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+The Project Gutenberg EBook of Earth and Sky Every Child Should Know, by 
+Julia Ellen Rogers
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Earth and Sky Every Child Should Know
+       Easy studies of the earth and the stars for any time and place
+
+Author: Julia Ellen Rogers
+
+Release Date: May 30, 2010 [EBook #32598]
+
+Language: English
+
+Character set encoding: ISO-8859-1
+
+*** START OF THIS PROJECT GUTENBERG EBOOK EARTH AND SKY ***
+
+
+
+
+Produced by Juliet Sutherland, Christine D. and the Online
+Distributed Proofreading Team at http://www.pgdp.net
+
+
+
+
+
+
+
+
+
+[Illustration: Pike's Peak, Colorado]
+
+  EARTH and SKY EVERY
+  CHILD SHOULD KNOW
+
+  EASY STUDIES OF THE EARTH AND THE
+  STARS FOR ANY TIME AND PLACE
+
+BY
+
+JULIA ELLEN ROGERS
+
+  AUTHOR OF
+  "THE TREE BOOK," "THE SHELL BOOK," "KEY TO THE NATURE
+  LIBRARY," "TREES EVERY CHILD SHOULD KNOW."
+
+  ILLUSTRATED BY
+  THIRTY-ONE PAGES OF PHOTOGRAPHS AND DRAWINGS
+
+[Illustration]
+
+  NEW YORK
+  GROSSET & DUNLAP
+  PUBLISHERS
+
+  COPYRIGHT, 1910, BY DOUBLEDAY, PAGE & COMPANY
+
+  PUBLISHED, OCTOBER, 1910
+
+  ALL RIGHTS RESERVED, INCLUDING THAT OF TRANSLATION
+  INTO FOREIGN LANGUAGES, INCLUDING THE SCANDINAVIAN
+
+
+
+
+ACKNOWLEDGMENTS
+
+
+A number of the photographs in this volume are used by permission of the
+American Museum of Natural History. The star maps and drawings of the
+constellations are by Mrs. Jerome B. Thomas. The poem by Longfellow,
+quoted in part, is with the permission of the publishers, Houghton,
+Mifflin & Co.
+
+       *       *       *       *       *
+
+
+
+
+CONTENTS
+
+
+  _PART I. THE EARTH_
+
+  PAGE
+
+  THE GREAT STONE BOOK                                          3
+
+  THE FOSSIL FISH                                               6
+
+  THE CRUST OF THE EARTH                                        9
+
+  WHAT IS THE EARTH MADE OF?                                   14
+
+  THE FIRST DRY LAND                                           22
+
+  A STUDY OF GRANITE                                           27
+
+  METAMORPHIC ROCKS                                            31
+
+  THE AIR IN MOTION                                            35
+
+  THE WORK OF THE WIND                                         44
+
+  RAIN IN SUMMER, _by Henry W. Longfellow_                     50
+
+  WHAT BECOMES OF THE RAIN?                                    51
+
+  THE SOIL IN FIELDS AND GARDENS                               58
+
+  THE WORK OF EARTHWORMS                                       63
+
+  QUIET FORCES THAT DESTROY ROCKS                              68
+
+  HOW ROCKS ARE MADE                                           72
+
+  GETTING ACQUAINTED WITH A RIVER                              78
+
+  THE WAYS OF RIVERS                                           84
+
+  THE STORY OF A POND                                          90
+
+  THE RIDDLE OF THE LOST ROCKS                                 93
+
+  THE QUESTION ANSWERED                                        96
+
+  GLACIERS AMONG THE ALPS                                      98
+
+  THE GREAT ICE SHEET                                         104
+
+  FOLLOWING SOME LOST RIVERS                                  110
+
+  THE MAMMOTH CAVE OF KENTUCKY                                114
+
+  LAND BUILDING BY RIVERS                                     121
+
+  THE MAKING OF MOUNTAINS                                     126
+
+  THE LAVA FLOOD OF THE NORTHWEST                             130
+
+  THE FIRST LIVING THINGS                                     134
+
+  AN ANCIENT BEACH AT EBB TIDE                                138
+
+  THE LIME ROCKS                                              147
+
+  THE AGE OF FISHES                                           152
+
+  KING COAL                                                   155
+
+  HOW COAL WAS MADE                                           160
+
+  THE MOST USEFUL METAL                                       167
+
+  THE AGE OF REPTILES                                         175
+
+  THE AGE OF MAMMALS                                          180
+
+  THE HORSE AND HIS ANCESTORS                                 186
+
+  THE AGE OF MAN                                              194
+
+
+  _PART II. THE SKY_
+
+  EVERY FAMILY A "STAR CLUB"                                  201
+
+  THE DIPPERS AND THE POLE STAR                               207
+
+  CONSTELLATIONS YOU CAN ALWAYS SEE                           213
+
+  WINTER CONSTELLATIONS                                       219
+
+  ORION, HIS DOGS, AND THE BULL                               223
+
+  SEVEN FAMOUS CONSTELLATIONS                                 231
+
+  THE TWENTY BRIGHTEST STARS                                  239
+
+  HOW TO LEARN MORE                                           241
+
+
+
+
+ILLUSTRATIONS
+
+
+  Pike's Peak                                               _Frontispiece_
+
+                                                               FACING PAGE
+
+  Sand Dunes in Arizona                                                 44
+
+  Grand Ca�on of the Colorado                                           45
+
+  Castles Carved by Rain and Wind                                       52
+
+  Where All the Water Comes From                                        53
+
+  The Richest Gold and Silver Mines                                     72
+
+  Rocks Being Ground to Flour                                           73
+
+  A Pond Made by a Glacier                                              88
+
+  The Struggle Between a Stream and Its
+  Banks                                                                 89
+
+  Ripple Marks and Glacial Stri�                                       102
+
+  Glacial Grooves and Markings                                         103
+
+  Crinoid and Ammonite                                                 140
+
+  Fossil Corals, Coquina, Hippurite Limestone                          141
+
+  Fossil Fish                                                          152
+
+  Meteorite                                                            153
+
+  Eocene Fish and Trilobite                                            156
+
+  How Coal Was Made                                                    157
+
+  Banded Sandstone. Opalized Wood                                      176
+
+  Allosaurus                                                           177
+
+  A Three-horned Dinosaur                                              178
+
+  Remains of Brontosaurus                                              179
+
+  Restoration of Brontosaurus                                          182
+
+  Ornitholestes, a Small Dinosaur                                      183
+
+  A Mammoth                                                            186
+
+  An Ancestor of the Horse                                             187
+
+  Orion, His Dogs, and the Bull                                        214
+
+  Other Fanciful Sketches of Constellations                            215
+
+  The Sky in Winter                                                    244
+
+  The Sky in Spring                                                    244
+
+  The Sky in Summer                                                    244
+
+  The Sky in Autumn                                                    244
+
+
+
+
+PART I
+
+THE EARTH
+
+       *       *       *       *       *
+
+
+
+
+THE GREAT STONE BOOK
+
+    "The crust of our earth is a great cemetery where the rocks
+    are tombstones on which the buried dead have written their
+    own epitaphs. They tell us who they were, and when and where
+    they lived."--_Louis Agassiz._
+
+
+Deep in the ground, and high and dry on the sides of mountains, belts of
+limestone and sandstone and slate lie on the ancient granite ribs of the
+earth. They are the deposits of sand and mud that formed the shores of
+ancient seas. The limestone is formed of the decayed shells of animal
+forms that flourished in shallow bays along those shores. And all we
+know about the life of these early days is read in the epitaphs written
+on these stone tables.
+
+Under the stratified rocks, the granite foundations tell nothing of life
+on the earth. But the sea rolled over them, and in it lived a great
+variety of shellfish. Evidently the earliest fossil-bearing rocks were
+worn away, for the rocks that now lie on the granite show not the
+beginnings, but the high tide of life. The "lost interval" of which
+geologists speak was a time when living forms were few in the sea.
+
+In the muddy bottoms of shallow, quiet bays lie the shells and skeletons
+of the creatures that live their lives in those waters and die when they
+grow old and feeble. We have seen the fiddler crabs by thousands on
+such shores, young and old, lusty and feeble. We have seen the rocks
+along another coast almost covered by the coiled shells of little gray
+periwinkles, and big clumps of black mussels hanging on the piers and
+wharfs. All these creatures die, at length, and their shells accumulate
+on the shallow sea bottom. Who has not spent hours gathering dead shells
+which the tide has thrown up on the beach? Who has not cut his foot on
+the broken shells that lie in the sandy bottom we walk on whenever we go
+into the surf to swim or bathe?
+
+Read downward from the surface toward the earth's centre--
+
+
+TABLE OF CONTENTS
+
+
+  ------+----------------------+-----------+-----------------------
+  Part  | _Rock Systems_       | _Dominant | _Dominant Plants_
+        |                      | Animals_  |
+  ------+----------------------+-----------+-----------------------
+   VII. | Recent               | Man       | Flowering kinds
+        |{ Quaternary          |           |
+    VI. |           { Pliocene | Mammals   | Early flowering
+        |{ Tertiary { Miocene  |           |
+        |           { Eocene   |           |
+     V. | Mesozoic             | Reptiles  | Cycads
+    IV. | Carboniferous        | Amphibians| Ferns and Conifers
+   III. | Devonian             | Fishes    | Ferns
+    II. | Silurian             | Molluscs  | Seaweeds
+     I. | Fire-formed          | No life   | No life
+  ------+----------------------+-----------+-----------------------
+
+It is by dying that the creatures of the sea write their epitaphs. The
+mud or sand swallows them up. In time these submerged banks may be left
+dry, and become beds of stone. Then some of the skeletons and shells
+may be revealed in blocks of quarried stone, still perfect in form after
+lying buried for thousands of years.
+
+The leaves of this great stone book are the layers of rock, laid down
+under water. Between the leaves are pressed specimens--fossils of
+animals and plants that have lived on the earth.
+
+
+
+
+THE FOSSIL FISH
+
+
+I remember seeing a flat piece of stone on a library table, with the
+skeleton of a fish distinctly raised on one surface. The friend who
+owned this strange-looking specimen told me that she found it in a stone
+quarry. She brought home a large piece of the slate, and a stone-mason
+cut out the block with the fish in it, and her souvenir made a useful
+and interesting paper-weight.
+
+The story of that fish I heard with wonder, and have never forgotten. I
+had never heard of fossil animals or plants until my good neighbour
+talked about them. She showed me bits of stone with fern leaves pressed
+into them. One piece of hard limestone was as full of little sea-shells
+as it could possibly be. One ball of marble was a honeycombed pattern,
+and called "fossil coral."
+
+The fossil fish was once alive, swimming in the sea, and feeding on the
+things it liked to eat, as all happy fishes do. Near shore a river
+poured its muddy water into the sea, and the sandy bottom was covered
+with the mud that settled on it. At last the fish grew old, and perhaps
+a trifle stupid about catching minnows. It died, and sank to the muddy
+floor of the sea. Its horny bones were not dissolved by the water. They
+remained, and the mud filtered in and filled all the spaces. Soon the
+fish was buried completely by the sediment the river brought.
+
+Years, thousands of them, went by, and the layer of mud was so thick and
+heavy above the skeleton of the fish that it bore a weight of tons
+there, under the water. The close-packed mud became a stiff clay. After
+more thousands of years, the sea no longer came so far ashore, for the
+river had built up a great delta of land out of mud. The clay in which
+the fish was hidden hardened into slate. Water crept down in the loose
+upper layers, dissolving out salt and other minerals, and having harder
+work to soak through, the lower it went. The water left some of the
+minerals it had accumulated, calcium and silica and iron, in the lower
+rock beds, making them harder than they were before, and heavier and
+less porous.
+
+When the river gorge was cut through these layers of rock, the colour
+and thickness of each kind were laid bare. Centuries after, perhaps
+thousands of years, indeed, the quarrymen cut out the layers fit for
+building stones, flags for walks and slates for roofing. In the
+splitting of a flagstone, the long-buried skeleton of the fish came to
+light.
+
+Under our feet the earth lies in layers. Under the soil lie loose beds
+of clay and sand and gravel, and under these loose kinds of earth are
+close-packed clays, sandstones, limestones, shales, often strangely
+tilted away from the horizontal line, but variously fitted, one layer to
+another. Under these rocks lie the foundations of the earth--the
+fire-formed rocks, like granite. The depth of this original rock is
+unknown. It is the substance out of which the earth is made, we think.
+All the layered rocks are made of particles of the older ones, stolen by
+wind and water, and finally deposited on the borders of lakes and seas.
+So our rivers are doing to-day what they have always done--they are
+tearing down rocks, grinding and sifting the fragments, and letting them
+fall where the current of fresh water meets a great body of water that
+is still, or has currents contrary to that of the river.
+
+Do you see a little dead fish in the water? It is on the way to become a
+fossil, and the mud that sifts over it, to become a layer of slate.
+Every seashore buries its dead in layers of sand and mud.
+
+
+
+
+THE CRUST OF THE EARTH
+
+
+It is hard to believe that our solid earth was once a ball of seething
+liquid, like the red-hot iron that is poured out of the big clay cups
+into the sand moulds at an iron foundry. But when a mountain like
+Vesuvius sets up a mighty rumbling, and finally a mass of white-hot lava
+bursts from the centre and streams down the sides, covering the
+vineyards and olive orchards, and driving the people out of their homes
+in terror, it seems as if the earth's crust must be but a thin and frail
+affair, covering a fiery interior, which might at any time break out.
+The people who live near volcanoes might easily get this idea.
+
+But they do not. They go back as soon as the lava streams are cooled,
+and rebuild their homes, and plant more orchards and vineyards. "It is
+_so_ many years," say they to one another, "since the last bad eruption.
+Vesuvius will probably sleep now till we are dead and gone."
+
+This is good reasoning. There are few active volcanoes left on the
+earth, compared with the number that were once active, and long ago
+became extinct. And the time between eruptions of the active ones grows
+longer; the eruptions less violent. Terrible as were the recent
+earthquakes of San Francisco and Messina, this form of disturbance of
+the earth's crust is growing constantly less frequent. The earth is
+growing cooler as it grows older; the crust thickens and grows stronger
+as centuries pass. We have been studying the earth only a few hundred
+years. The crust has been cooling for millions of years, and
+mountain-making was the result of the shrinking of the crust. That
+formed folds and clefts, and let masses of the heated substance pour out
+on the surface.
+
+My first geography lesson I shall never forget. The new teacher had very
+bright eyes and _such_ pretty hands! She held up a red apple, and told
+us that the earth's substance was melted and burning, inside its crust,
+which was about as thick, in proportion to the size of the globe, as the
+skin of the apple. I was filled with wonder and fear. What if we
+children jumped the rope so hard as to break through the fragile shell,
+and drop out of sight in a sea of fiery metal, like melted iron? Some of
+the boys didn't believe it, but they were impressed, nevertheless.
+
+The theory of the heated interior of the earth is still believed, but
+the idea that flames and bubbling metals are enclosed in the outer layer
+of solid matter has generally been abandoned. The power that draws all
+of its particles toward the earth's centre is stated by the laws of
+gravitation. The amount of "pull" is the measure of the weight of any
+substance. Lift a stone, and then a feather pillow, much larger than
+the stone. One is strongly drawn to the earth; the other not. One is
+_heavy_, we say, the other _light_.
+
+If a stone you can pick up is heavy, how much heavier is a great boulder
+that it takes a four-horse team to haul. What tremendous weight there is
+in all the boulders scattered on a hillside! The hill itself could not
+be made level without digging away thousands of tons of earth. The
+earth's outer crust, with its miles in depth of mountains and level
+ground, is a crushing weight lying on the heated under-substance. Every
+foot of depth adds greatly to the pressure exerted upon the mass, for
+the attraction of gravitation increases amazingly as the centre of the
+earth is approached.
+
+It is now believed that the earth is solid to its centre, though heated
+to a high degree. Terrific pressure, which causes this heat, is exerted
+by the weight of the crust. A crack in the crust may relieve this
+pressure at some point, and a mass of substance may be forced out and
+burst into a flaming stream of lava. Such an eruption is familiar in
+volcanic regions. The fact that red-hot lava streams from the crater of
+Vesuvius is no proof that it was seething and bubbling while far below
+the surface.
+
+Volcanoes, geysers, and hot springs prove that the earth's interior is
+hot. The crust is frozen the year around in the polar regions, and never
+between the Tropics of Cancer and Capricorn. The sun's rays produce our
+different climates, but they affect only the surface. Underground, there
+is a rise of a degree of temperature for every fifty feet one goes
+down. The lowest mine shaft is about a mile deep. That is only one
+four-thousandth of the distance to the earth's centre.
+
+By an easy computation we could locate the known melting-point for
+metals and other rock materials. But one degree for each fifty feet of
+depth below the surface may not be correct for the second mile, as it is
+for the first. Again, the melting-point is probably a great deal higher
+for substances under great pressure. The weight of the crust is a burden
+the under-rocks bear. Probably the pressure on every square inch reaches
+thousands of tons. Could any substance become liquid with such a weight
+upon it, whatever heat it attained? Nobody can answer this question.
+
+The theory that volcanoes are chimneys connecting lakes of burning lava
+with the surface of the earth is discredited by geologists. The weight
+of the overlying crust would, they think, close such chambers, and
+reduce liquids to a solid condition.
+
+Since the first land rose above the sea, the crust of the earth has
+gradually become more stable, but even now there is scarcely a day when
+the instruments called seismographs do not record earthquake shocks in
+some part of the earth; and the outbreaks of Vesuvius and �tna, the
+constant boiling of lava in the craters of the Hawaiian Islands and
+other volcanic centres, prove that even now the earth's crust is very
+thin and unstable. The further back in time we go, the thinner was the
+crust, the more frequent the outbursts of volcanic activity, the more
+readily did wrinkles form.
+
+The shores of New Jersey and of Greenland are gradually sinking, and the
+sea coming up over the land. Certain parts of the world are gradually
+rising out of the sea. In earlier times the rising or the sinking of
+land over large areas happened much more frequently than now.
+
+
+
+
+WHAT IS THE EARTH MADE OF?
+
+
+"Baking day" is a great institution in the comfortable farm life of the
+American people. The big range oven is not allowed to grow cold until
+rows of pies adorn the pantry shelves, and cakes, tarts, and generous
+loaves of bread are added to the store. Cookies, perhaps, and a big pan
+full of crisp, brown doughnuts often crown the day's work. No gallery of
+art treasures will ever charm the grown-up boys and girls as those
+pantry shelves charmed the bright-eyed, hungry children, who were
+allowed to survey the treasure-house, and sample its good things while
+they were still warm.
+
+You could count a dozen different kinds of cakes and pies, rolls and
+cookies on those pantry shelves, yet several of them were made out of
+the same dough. Instead of a loaf of bread, mother could make two or
+three kinds of coffee cake, or cinnamon rolls, or currant buns, or
+Parker-House rolls. Even the pastry, which made the pies and tarts, was
+not so different from the bread dough, for each was made of flour, and
+contained, besides the salt, "shortening," which was butter or lard.
+Sugar was used in everything, from the bread, which had a
+table-spoonful, to the cookies, which were finished with a sifting of
+sugar on top.
+
+How much of the food we eat is made of a very few staple
+foodstuffs,--starch, sugar, fats! So in the wonderful earth and all that
+grows out of it and lives upon it. Only seventy different elements have
+been discovered, counting, besides the earth, the water and the air, and
+even the strange wandering bodies, called meteorites, that fall upon the
+earth out of the sky. Like the flour in the different cakes and pies,
+the element carbon is found in abundance and in strangely different
+combinations. As a gas, in combination with oxygen, it is breathed out
+of our lungs, and out of chimneys where coal and wood are burned. It
+forms a large part of the framework of trees and other plants, and
+remains as charcoal when the wood is slowly burned under a close
+covering. There is a good proportion of carbon in animal bodies, in the
+bones as well as the soft parts, and carbon is plentiful in the mineral
+substances of the earth.
+
+The chemist is the man who has determined for us the existence and the
+distribution of the seventy elements. He finds them in the solid
+substances of the globe and in the water that covers four-fifths of its
+surface; in the atmosphere that covers sea and land, and in all the
+living forms of plants and animals that live in the seas and on the
+land. By means of an instrument called the spectroscope, the heavenly
+bodies are proved to be made of the same substances that are found in
+the rocks. The sun tells what it is made of, and one proof that the
+earth is a child of the sun is in the fact that the same elements are
+found in the substance of both.
+
+Of the seventy elements, the most important are these: Oxygen, silicon,
+aluminum, iron, manganese, calcium, magnesium, potassium, sodium,
+carbon, hydrogen, phosphorus, sulphur, chlorine, nitrogen.
+
+_Oxygen_ is the most plentiful and the most important element. One-fifth
+of the air we breathe is oxygen; one-third of the water we drink. The
+rock foundations of the earth are nearly one-half oxygen. No fire can
+burn, no plant or animal can grow, or even decay after it dies, unless
+oxygen is present and takes an active part in each process. Strangely
+enough, this wonderful element is invisible. We open a window, and pure
+air, rich in oxygen, comes in and takes the place of the bad air but we
+cannot see the change. Water we see, but if the oxygen and the hydrogen
+which compose the colourless liquid were separated, each would become at
+once an invisible gas. The oxygen of solid rocks exists only in
+combination with other elements.
+
+_Silicon_ is the element which, united with oxygen, makes the rock
+called quartz. On the seashore the children are busy with their pails
+and shovels digging in the white, clean sand. These grains are of
+quartz,--fine crystals of a rock which forms nearly three-quarters of
+the solid earth's substance. Not only in rocks, but out here in the
+garden, the soil is full of particles of sand. You cannot get away from
+it.
+
+_Aluminum_ is a light, bluish-white metal which we know best in
+expensive cooking utensils. It is more abundant even than iron, but
+processes of extracting it from the clay are still expensive. It is
+oftenest found in combination with oxygen and silicon. While nearly
+one-tenth of the earth's crust is composed of the metal aluminum,
+four-fifths and more is composed of the minerals called silicates of
+aluminum--oxygen, silicon, and aluminum in various combinations. It is
+more plentiful than any other substance in rocks and in the clays and
+ordinary soils, which are the finely ground particles of rock material.
+
+_Iron_ is one of the commonest of elements. We know it by its red
+colour. A rusty nail is covered with oxide of iron, a combination which
+is readily formed wherever iron is exposed to the action of water or
+air. You have seen yellowish or red streaks in clefts of the rocks. This
+shows where water has dissolved out the iron and formed the oxide. The
+red colour of New Jersey soil is due to the iron it contains. Indeed,
+the whole earth's crust is rich in iron which the water easily
+dissolves. The roots of plants take up quantities of iron in solution
+and this mounts to the blossoms, leaves, and fruit. The red or yellow
+colour of autumn leaves, of apples, of strawberries, of tulips, and of
+roses, is produced by iron. The rosy cheeks of children are due to iron
+in the food they eat and in the water they drink. The doctor but follows
+the suggestion of nature when he gives a pale and listless person a
+tonic of iron to make his blood red.
+
+Iron is rarely found free, but it forms about five per cent. of the
+crust of the earth, and it is believed to form at least one-fifth of the
+unknown centre of the earth, the bulk of the globe, the weight of which
+we know, but concerning the substance of which we can say little that is
+positive.
+
+_Manganese_ is not a conspicuous element, but is found united with
+oxygen in purplish or black streaks on the sides of rocks. It is
+somewhat like iron, but much less common.
+
+_Calcium_ is the element that is the foundation of limestones. The
+skeletons and shells of animals are made of calcite, a common mineral
+formed by the uniting of carbon, oxygen, and calcium. Marbles are,
+perhaps, the most permanent form of the limestone rocks. "Hard" water
+has filtered through rocks containing calcite, and absorbed particles of
+this mineral. From water thus impregnated, all animal life on the earth
+obtains its bone-building and shell-building materials.
+
+_Carbon_ forms a large part of the tissues of plants and animals, and in
+the remains of these it is chiefly found in the earth's crust. When
+these burn or decay, the carbon remains as charcoal or escapes to the
+air in union with oxygen as the well known carbonic acid gas. This is
+one of the most important foods of plants. Joined with calcium it forms
+the mineral calcite, or carbonate of lime.
+
+_Hydrogen_ is one of the two gases that unite to form water. Oxygen is
+the other. Many kinds of rock contain a considerable amount of water.
+Surface water sinks into porous soils and rocks, and accumulates in
+pockets and veins which feed springs, and are the reserve water supply
+that keeps our rivers flowing, even through dry weather. More water is
+held by absorption in the earth's solid crust than in all the oceans and
+seas and great lakes.
+
+Hydrogen, combined with carbon, occurs in solid rocks where the remains
+of plants and animals have slowly decayed. From such processes the
+so-called hydrocarbons, rock oil and natural gas, have accumulated. When
+such decay goes on above ground, these valuable products escape into the
+air. Marsh gas, whose feeble flame above decaying vegetation is the
+will-o'-the-wisp of swamps, is an example.
+
+_Magnesium_, _potassium_, and _sodium_ are found in equal quantities in
+the earth's crust, but never free. In union with chlorine, each forms a
+soluble salt, and is thus found in water. Common salt, chloride of
+sodium, is the most abundant of these. Water dissolves salt out of the
+rocks, and carries it into the sea. Clouds that rise by the evaporation
+of ocean water leave the salt behind, hence the seas are becoming more
+and more salty, for the rivers carry salt to the oceans, which hold fast
+all they get.
+
+_Phosphorus_ is an element found united with oxygen in the tissues of
+both plants and animals. It is most abundant in bones. Rocks containing
+fossil bones are rich in lime phosphates, which are important commercial
+fertilizers for enriching the soil. Beds of these rocks are found and
+mined in South Carolina and elsewhere.
+
+_Sulphur_ is well known as a yellow powder found most plentifully in
+rocks that are near volcanoes. It is a needed element in plant and
+animal bodies. It occurs in rocks, united with many different elements.
+In union with oxygen and a metal it forms the group of minerals called
+sulphates. In union with iron it forms sulphide of iron. The "fool's
+gold" which Captain John Smith's colonists found in the sand at
+Jamestown, was this worthless iron pyrites.
+
+_Chlorine_ is a greenish, yellow gas, very heavy, and dangerous to
+inhale. If it gets into the lungs, it settles into the lowest levels,
+and one must stand on one's head to get it out. As an element of the
+earth's crust it is not very plentiful, but it is a part of all the
+chlorides of sodium, magnesium, and potassium. In salt, it forms two per
+cent. of the sea water. It is much less abundant in the rocks.
+
+To these elements we might add _nitrogen_, that invisible gas which
+forms nearly four-fifths of our atmosphere, and is a most important
+element of plant food in the soil. Most of the seventy elements are very
+rare. Many are metals, like gold and iron and silver. Some are not
+metals. Some are solid. A few are liquid, like the metal mercury, and
+several are gaseous. Some are free and pure, and show no disposition to
+unite with others. Nuggets of gold are examples of this. Some exist only
+in union with other elements. This is the common rule among the
+elements. Changes are constantly going on. The elements are constantly
+abandoning old partnerships and forming new ones. Growth and decay of
+plant and animal life are but parts of the great programme of constant
+change which is going on and has been in progress since the world
+began.
+
+
+
+
+THE FIRST DRY LAND
+
+
+When the earth's crust first formed it was still hot, though not so hot
+as when it was a mass of melted, glowing substance. As it moved through
+the cold spaces of the sky, it lost more heat and its crust became
+thicker. At length the cloud masses became condensed enough to fall in
+torrents of water, and a great sea covered all the land. This was before
+any living thing, plant or animal, existed on our planet. Can you
+imagine the continents and islands that form the land part of a map or
+globe suddenly overwhelmed by the oceans, the names and boundaries of
+which you have taken such pains to learn in the study of geography? The
+globe would be one blank of blue water, and geography would be
+abolished--and there would be nobody to study it. Possibly the fishes in
+the sea might not notice any change in the course of their lives, except
+when they swam among the ruins of buried cities and peered into the
+windows of high buildings, or wondered what new kind of seaweed it was
+when they came upon a submerged forest.
+
+In that old time of the great sea that covered the globe, we are told
+that there was a dense atmosphere over the face of the deep. So things
+were shaping themselves for the far-off time when life should exist,
+not only in the sea, where the first life did appear, but on land. But
+it took millions of years to fit the earth for living things.
+
+The cooling of the earth made it shrink, and the crust began to be
+folded into gentle curves, as the skin of a shrunken apple becomes
+wrinkled on the flesh. Some of these creases merely changed the depth of
+water on the sea bottom; but one ridge was lifted above the water. The
+water parted and streamed down its sloping sides, and a granite reef,
+which shone in the sunshine, became the first dry land. It lay east and
+west, and stretched for many miles. It is still dry land and is a part
+of our own continent. Now it is but a small part of the country, but it
+is known by geologists, who can tell its boundaries, though newer land
+joins it on every side. It is named the Laurentian Hills, on geological
+maps. Its southern border reaches along the northern boundary of the
+Great Lakes to the head-waters of the Mississippi River.
+
+From this base, two ridges are lifted, forming a colossal V. One extends
+northeast to Nova Scotia; the other northwest to the Arctic seas. The V
+encloses Hudson Bay.
+
+Besides this first elongated island of bare rocks, land appeared in a
+strip where now the Blue Ridge Mountains stretch from New England to
+Georgia. The other side of the continent lifted up two folds of the
+crust above sea level. They are the main ridges of the Colorado and the
+Wasatch Mountains. Possibly the main ridge of the Sierra Nevada rose
+also at this time. The Ozark group of mountains, too, showed as a few
+island peaks above the sea.
+
+These first rocks were rapidly eaten away, for the atmosphere was not
+like ours, but heavily charged with destructive gases, which did more,
+we believe, to disintegrate the exposed rock surfaces than did the two
+other forces, wind and water, combined. The sediment washed down to the
+sea by rains, accumulated along the shores, filling the shallows and
+thus adding to the width of the land areas. The ancient granite ridge of
+the Laurentian Hills is now low, and slopes gently. This is true of all
+very old mountains. The newer ones are high and steep. It takes time to
+grind down the peaks and carry off the waste material loosened by
+erosion.
+
+Far more material than could have been washed down the slopes of the
+first land ridges came directly from the interior of the earth, and
+spread out in vast, submarine layers upon the early crust. Volcanic
+craters opened under water, and poured out liquid mineral matter, that
+flowed over the sea bottom before it cooled. Imagine the commotion that
+agitated the water as these submerged chimneys blew off their lids, and
+discharged their fiery contents! It was long before the sea was cool
+enough to be the home of living things.
+
+The layers of rock that formed under the sea during this period of the
+earth's history are of enormous thickness. They were four or five miles
+deep along the Laurentian Hills. They broadened the original granite
+ridge by filling the sea bottom along the shores. The backbones of the
+Appalachian system and the Cordilleras were built up in the same
+way--the oldest rocks were worn away, and their d�bris built up newer
+ones in strata.
+
+When these layers of rock became dry land, the earth's crust was much
+more stable and cool than it had ever been before. The vast
+rock-building of that era equals all that has been done since. The
+layers of rocks formed since then do not equal the total thickness of
+these first strata. So we believe that the time required to build those
+Arch�an rock foundations equals or surpasses the vast period that has
+elapsed since the Arch�an strata were formed.
+
+The northern part of North America has grown around those old granite
+ridges by the gradual rising of the shores. The geologist may walk along
+the Laurentian Hills, that parted the waters into a northern and a
+southern ocean. He crosses the rocky beds deposited upon the granite;
+then the successive beds formed as the land rose and the ocean receded.
+Age after age is recorded in the rocks. Gradually the sea is crowded
+back, and the land masses, east, west, and north, meet to form the
+continent. Nowhere on the earth are the steps of continental growth
+shown in unbroken sequence as they are in North America.
+
+How long ago did those first islands appear above the sea? Nobody
+ventures a definite answer to this question. No one has the means of
+knowing. But those who know most about it estimate that at the least one
+hundred million years have passed since then--one hundred thousand
+thousand years!
+
+
+
+
+A STUDY OF GRANITE
+
+
+In Every village cemetery it is easy to find shafts of gray or speckled
+granite, the polished surfaces of which show that the granite is made of
+small bits of different coloured minerals, cemented together into solid
+rock. Outside the gate you will usually find a place where monuments and
+gravestones may be bought. Here there is usually a stonecutter chipping
+away on a block with his graving tools. He is a man worth knowing, and
+because his work is rather monotonous he will probably be glad to talk
+to a chance visitor and answer questions about the different kinds of
+stone on which he works.
+
+There are bits of granite lying about on the ground. If you have a
+hand-glass of low power, such as the botany class uses to examine the
+parts of flowers, it will be interesting to look through it and see the
+magnified surface of a flake of broken granite. Here are bits of glassy
+quartz, clear and sparkling in the sun. Black and white may be all the
+colours you make out in this specimen, or it may be that you see specks
+of pink, dark green, gray, and smoky brown, all cemented together with
+no spaces that are not filled. The particles of quartz are of various
+colours, and are very hard. They scratch glass, and you cannot scratch
+them with the steel point of your knife, as you can scratch the other
+minerals associated with the grains of quartz.
+
+Granite is made of quartz, feldspar, and mica, sometimes with added
+particles of hornblende. Feldspar particles have as wide a range of
+colour as quartz, but it is easy to tell the two apart. A knife will
+scratch feldspar, as it is not so hard as quartz. The crystals of
+feldspar have smooth faces, while quartz breaks with a rough surface as
+glass does. Feldspar loses its glassy lustre when exposed to the
+weather, and becomes dull, with the soft lustre of pearl.
+
+Mica may be clear and glassy, and it ranges in colour from transparency
+through various shades of brown to black. It has the peculiarity of
+splitting into thin, leaf-like, flexible sheets, so it is easy to find
+out which particles in a piece of granite are mica. One has only to use
+one's pocket knife with a little care. Hornblende is a dark mineral
+which contains considerable iron. It is found in lavas and granites,
+where it easily decays by the rusting of the iron. It is not unusual to
+see a rough granite boulder streaked with dark red rust from this cause.
+
+The crumbling of granite is constantly going on as a result of the
+exposure of its four mineral elements to the air. Quartz is the most
+stable and resistant to weathering. Soil water trickling over a granite
+cliff has little effect on the quartz particles; but it dissolves out
+some of the silicon. The bits of feldspar are even more resistant to
+water than quartz is, but the air causes them to decay rapidly, and
+finally to fall away in a sort of mealy clay. Mica, like feldspar,
+decays easily. Its substance is dissolved by water and carried away to
+become a kind of clay. The hornblende rusts away chiefly under the
+influence of moist air and trickling water.
+
+We think of granite as a firm, imperishable kind of rock, and use it in
+great buildings like churches and cathedrals that are to stand for
+centuries. But the faces that are exposed to the air suffer, especially
+in regions having a moist climate. The signs of decay are plainly
+visible on the outer surfaces of these stones. Fortunate it is that the
+weathering process cannot go very deep.
+
+The glassy polish on a smooth granite shaft is the silicon which acts as
+a cement to bind all the particles together. It is resistant to the
+weather. A polished shaft will last longer than an unpolished one.
+
+Granites differ in colouring because the minerals that compose them, the
+feldspars, quartzes, micas, and hornblendes, have each so wide a range
+of colour. Again, the proportions of the different mineral elements vary
+greatly in different granites. A banded granite the colours of which
+give it a stratified appearance is called a gneiss.
+
+We have spoken before of the seventy elements found in the earth's
+crust. A mineral is a union of two or more of these different elements;
+and we have found four minerals composing our granite rock. It may be
+interesting to go back and inquire what elements compose these four
+minerals. Quartz is made of silicon and oxygen. Feldspar is made of
+silicon, oxygen, and aluminum. Mica is made of silicon, oxygen, and
+carbon, with some mingling of potassium and iron and other elements in
+differing proportions. Hornblende is made of silicon, oxygen, carbon,
+and iron.
+
+The crumbling of a granite rock separates the minerals that compose it,
+reducing some to the condition of clay, others to grains of sand. Some
+of the elements let go their union and become free to form new unions.
+Water and wind gather up the fragments of crumbling granite and carry
+them away. The feldspar and mica fragments form clay; the quartz
+fragments, sand. All of the sandstones and slates, the sand-banks and
+sand beaches, are made out of crumbled granite, the rocky foundations of
+the earth.
+
+
+
+
+METAMORPHIC ROCKS
+
+
+In the dawn of life on the earth, soft-bodied creatures, lowest in the
+scale of being, inhabited the sea. The ancient volcanoes the
+subterranean eruptions of which had spread layers of mineral substance
+on the ocean floor, and heated the water to a high degree, had subsided.
+The ocean was sufficiently cool to maintain life. The land was being
+worn down, and its d�bris washed into the ocean. The first sand-banks
+were accumulating along sandy shores. The finer sediment was carried
+farther out and deposited as mud-banks. These were buried under later
+deposits, and finally, by the rising of the earth's crust, they became
+dry land. Time and pressure converted the sand-banks into sandstones;
+the mud-banks into clay. The remains of living creatures utterly
+disappeared, for they had no hard parts to be preserved as fossils.
+
+The shrinking of the earth's crust had crumpled into folds of the utmost
+complexity those horizontal layers of lava rock poured out on the ocean
+floor. Next, the same forces attacked the thick rock layers formed out
+of sediment--the aqueous or water-formed sandstones and clays.
+
+The core of the globe contracts, and the force that crumples the crust
+to fit the core generates heat. The alkaline water in the rocks joins
+with the heat produced by the crumpling and crushing forces, acting
+downward, and from the sides, to transform pure sandstone into glassy
+quartzite, and clay into slate. In other words, water-formed rocks are
+baked until they become fire-formed rocks. They are what the geologist
+calls _metamorphic_, which means _changed_.
+
+In many mountainous regions there are breaks through the strata of
+sandstone and slates and limestones, through which streams of lava have
+poured forth from the heated interior. Along the sides of these fissures
+the hot lava has changed all the rocks it touched. The heat of the
+volcanic rock matter has melted the silica in the sand, which has
+hardened again into a crystalline substance like glass.
+
+Have you ever visited a brick-yard? Here men are sifting clay dug out of
+a pit or the side of a hill, adding sand from a sand-bank, and in a big
+mixing box, stirring these two "dry ingredients" with water into a thick
+paste. This dough is moulded into bricks, sun-dried, and then baked in
+kilns themselves built of bricks. At the end of the baking, the soft,
+doughy clay block is transformed into a hard, glassy, or dull brick.
+From aqueous rock materials, fire has produced a metamorphic rock.
+Volcanic action is imitated in this common, simple process of
+brickmaking.
+
+Milwaukee brick is made of clay that has no iron in it. For this reason
+the bricks are yellow after baking. Most bricks are red, on account of
+the iron in the clay, which is converted into a red oxide, or rust, by
+water and heat.
+
+Common flower pots and the tiles used in draining wet land are not
+glazed, as hard-burned bricks are. The baking of these clay things is
+done with much less heat. They are left somewhat porous. But the tiles
+of roofs are baked harder, and get a surface glaze by the melting of the
+glassy particles of the sand.
+
+As bricks vary in colour and quality according to the materials that
+compose them, so the metamorphic rocks differ. The white sand one sees
+on many beaches is largely quartz. This is the substance of pure, white
+sandstone. Metamorphism melts the silica into a glassy liquid cement;
+the particles are bound close together on cooling. The rock becomes a
+white, granular quartzite, that looks like loaf sugar. If banded, it is
+called gneiss. Such rocks take a fine polish.
+
+Pure limestone is also white and granular. When metamorphosed by heat,
+it becomes white marble. The glassy cement that holds the particles of
+lime carbonate shows as the glaze of the polished surface. It is silica.
+One sees the same mineral on the face of polished granite.
+
+Clays are rarely pure. Kaolin is a white clay which, when baked, becomes
+porcelain. China-ware is artificially metamorphosed kaolin. In the
+early rocks the clay beds were transformed by heat into jasper and
+slates. In beds where clay mingled with sand, in layers, gneiss was
+formed. If mica is a prominent element, the metamorphic rock is easily
+parted into overlapping, scaly layers. It is a mica schist. If
+hornblende is the most abundant mineral, the same scaly structure shows
+in a dark rock called hornblende schist, rich in iron. A schist
+containing much magnesia is called serpentine.
+
+The bricks of the wall, the tiles on the roof, the flower pots on the
+window sill, and the dishes on the breakfast table, are examples of
+metamorphic rocks made by man's skill, by the use of fire and water
+acting on sand and clay. Pottery has preserved the record of
+civilization, from the making of the first crude utensils by cave men to
+the finest expression of decorative art in glass and porcelain.
+
+The choicest material of the builder and the sculptor is limestone baked
+by the fires under the earth's crust into marble. The most enduring of
+all the rocks are the foundation granite, and the metamorphic rocks that
+lie next to them. Over these lie thick layers of sedimentary rocks laid
+down by water. In them the record of life on the earth is written in
+fossils.
+
+
+
+
+THE AIR IN MOTION
+
+
+Most of the beautiful things that surround us and make our lives full of
+happiness appeal to one or more of our five senses. The green trees we
+can see, the bird songs we hear, the perfume of honey-laden flowers we
+smell, the velvety smoothness of a peach we feel, and its rich pulp we
+taste. But over all and through all the things we see and feel and hear
+and taste and smell, is the life-giving air, that lies like a blanket,
+miles in depth, upon the earth. The substance which makes the life of
+plants and animals possible is, when motionless, an invisible,
+tasteless, odourless substance, which makes no sound and is not
+perceptible to the touch.
+
+Air fills the porous substance of the earth's crust for a considerable
+distance, and even the water has so much air in it that fishes are able
+to breathe without coming to the surface. It is not a simple element,
+like gold, or carbon, or calcium, but is made up of several elements,
+chief among which are nitrogen and oxygen. Four-fifths of its bulk is
+nitrogen and one-fifth oxygen. There is present in air more or less of
+watery vapour and of carbon dioxide, the gas which results from the
+burning or decay of any substance. Although no more than one per cent.
+of the air that surrounds us is water, yet this is a most important
+element. It forms the clouds that bear water back from the ocean and
+scatter it in rain upon the thirsty land. Solid matter in the form of
+dust, and soot from chimneys, accumulates in the clouds and does a good
+work in condensing the moisture and causing it to fall.
+
+It is believed that the air reaches to a height of one hundred to two
+hundred miles above the earth's surface. If a globe six feet in diameter
+were furnished with an atmosphere proportionately as deep as ours, it
+would be about an inch in depth. At the level of the sea the air reaches
+its greatest density. Two miles above sea-level it is only two-thirds as
+dense. On the tops of high mountains, four or five miles above sea
+level, the air is so rarefied as to cause the blood to start from the
+nostrils and eyelids of explorers. The walls of the little blood-vessels
+are broken by the expansion of the air that is inside. At the sea-level
+air presses at the rate of fifteen pounds per square foot in all
+directions. As one ascends to higher levels, the air pressure becomes
+less and less.
+
+The barometer is the instrument by which the pressure of air is
+measured. A glass tube, closed at one end, and filled with mercury, the
+liquid metal often called quicksilver, is inverted in a cup of the same
+metal, and so supported that the metal is free to flow between the two
+vessels. The pressure of air on the surface of the mercury in the cup is
+sufficient at the sea-level to sustain a column of mercury thirty
+inches high in the tube. As the instrument is carried up the side of a
+mountain the mercury falls in the tube. This is because the air pressure
+decreases the higher up we go. If we should descend into the shaft of
+the deepest mine that reaches below the sea level, the column of air
+supported by the mercury in the cup would be a mile higher, and for this
+reason its weight would be correspondingly greater. The mercury would
+thus be forced higher in the tube than the thirty-inch mark, which
+indicates sea-level.
+
+Another form of barometer often seen is a tube, the lower and open end
+of which forms a U-shaped curve. In this open end the downward pressure
+of the air rests upon the mercury and holds it up in the closed end,
+forcing it higher as the instrument is carried to loftier altitudes. At
+sea level a change of 900 feet in altitude makes a change of an inch in
+the height of the mercury in the column. The glass tube is marked with
+the fractions of inches, or of the metre if the metric system of
+measurements is used.
+
+It is a peculiarity of air to become heated when it is compressed, and
+cooled when it is allowed to expand again. It is also true that when the
+sun rises, the atmosphere is warmed by its rays. This is why the hottest
+part of the day is near noon when the sun's rays fall vertically. The
+earth absorbs a great deal of the sun's heat in the daytime and through
+the summer season. When it cools this heat is given off, thus warming
+the surrounding atmosphere. In the polar regions, north and south, the
+air is far below freezing point the year round. In the region of the
+Equator it rarely falls below 90 degrees, a temperature which we find
+very uncomfortable, especially when there is a good deal of moisture in
+the air.
+
+If we climb a mountain in Mexico, we leave the sultry valley, where the
+heat is almost unbearable, and very soon notice a change. For every
+three hundred feet of altitude we gain there is a fall of one degree in
+the temperature. Before we are half way up the slope we have left behind
+the tropical vegetation, and come into a temperate zone, where the
+plants are entirely different from those in the lower valley. As we
+climb, the vegetation becomes stunted, and the thermometer drops still
+lower. At last we come to the region of perpetual snow, where the
+climate is like that of the frozen north.
+
+So we see that the air becomes gradually colder as we go north or south
+from the Equator, and the same change is met as we rise higher and
+higher from the level of the sea.
+
+It is only when air is in motion that we can feel and hear it, and there
+are very few moments of the day, and days of the year, when there is not
+a breeze. On a still day fanning sets the air in motion, and creates a
+miniature breeze, the sound of which we hear in the swishing of the fan.
+The great blanket of air that covers the earth is in a state of almost
+constant disturbance, because of the lightness of warm air and the
+heaviness of cold air. These two different bodies are constantly
+changing places. For instance, the heated air at the Equator is
+constantly being crowded upward by cold air which settles to the level
+of the earth. Cold streams of air flow to the Tropics from north and
+south of the Equator, and push upward the air heated by the sun.
+
+This constant inrush of air from north and south forms a double belt of
+constant winds. If the earth stood still, no doubt the direction would
+be due north and due south for these winds; but the earth rotates
+rapidly from west to east upon its axis, carrying with it everything
+that is securely fastened to the surface: the trees, the houses, etc.
+But the air is not a part of the earth, not even so much as the seas,
+the waters of which must stay in their proper basins, and be whirled
+around with other fixed objects. The earth whirls so rapidly that the
+winds from north and south of the Equator lag behind, and thus take a
+constantly diagonal direction. Instead of due south the northern belt of
+cold air drifts south-west and the southern belt drifts northwest. These
+are called the Trade Winds. Near the Equator they are practically east
+winds.
+
+The belt of trade winds is about fifty degrees wide. It swings northward
+in our summer and southward in our winter, its centre following the
+vertical position of the sun. Near the centre of the course which marks
+the meeting of the northern with the southern winds is a "Belt of
+Calms" where the air draws upward in a strong draught. The colder air of
+the trade winds is pushing up the columns of light, heated air. This
+strip is known by sailors as "the Doldrums," or "the region of
+equatorial calms." Though never wider than two or three hundred miles,
+this is a region dreaded by captains of sailing-vessels, for they often
+lie becalmed for weeks in an effort to reach the friendly trade winds
+that help them to their desired ports. Vessels becalmed are at the mercy
+of sudden tempests which come suddenly like thunder-storms, and
+sometimes do great damage to vessels because they take the sailors
+unawares and allow no time to shorten sail.
+
+Until late years the routes of vessels were charted so that sailors
+could take advantage of the trade winds in their long voyages. It was
+necessary in the days of sailing-vessels for the captain to understand
+the movements of winds which furnished the motive power that carried his
+vessel. Fortunate it was for him that there were steady winds in the
+temperate zones that he could take advantage of in latitudes north of
+the Tropic of Cancer and south of the Tropic of Capricorn. What becomes
+of the hot air that rises in a constant stream above the "Doldrums,"
+pushed up by the cooler trade winds that blow in from north and south?
+Naturally this air cannot ascend very high, for it soon reaches an
+altitude in which its heat is rapidly lost, and it would sink if it
+were not constantly being pushed by the rising column of warm air under
+it. So it turns and flows north and south at a level above the trade
+winds. Not far north of the Tropic of Cancer it sinks to the level of
+sea and land, and forms a belt of winds that blows ships in a
+northeasterly direction. Between trades and anti-trades is another zone
+of calms,--near the Tropics of Cancer and of Capricorn.
+
+The land masses of the continents with their high mountain ranges
+interfere with these winds, especially in the northern hemisphere, but
+in the Southern Pacific and on the opposite side of the globe the
+"Roaring Forties," as these prevailing westerly winds are known by the
+sailors, have an almost unbroken waste of seas over which they blow. In
+the long voyages between England and Australia, and in the Indian trade,
+the ships of England set their sails to catch the roaring forties both
+going and coming. They accomplish this by sailing past the Cape of Good
+Hope on the outward voyage and coming home by way of Cape Horn, thus
+circling the globe with every trip. In the North Atlantic, traffic is
+now mostly carried on in vessels driven by engines, not by sails. Yet
+the westerly winds that blow from the West Indies diagonally across the
+Atlantic are still useful to all sailing craft that are making for
+British ports.
+
+From the north and from the south cold air flows down into the regions
+of warmer climate. These polar winds are not so important to sea
+commerce, but they do a great work in tempering the heat in the
+equatorial regions. We cannot know how much our summers are tempered by
+the cool breath of winds that blow over polar ice-fields. And the cold
+regions of the earth, in their brief summer, enjoy the benefits of the
+warm breezes that flow north and south from the heated equatorial
+regions.
+
+The land, north and south, is made habitable by the clouds. They gather
+their burdens of vapour from the warm seas, the wind drifts them north
+and south, where they let it fall in rains that make and keep the earth
+green and beautiful. From the clouds the earth gathers, like a great
+sponge, the water that stores the springs and feeds rivers and lakes.
+How necessary are the winds that transport the cloud masses!
+
+The air is the breath of life to all living things on our planet. Mars
+is one of the sun's family so provided. Plants or animals could probably
+live on the planet Mars. Do we think often enough of this invisible,
+life-giving element upon which we depend so constantly?
+
+The open air which the wind purifies by keeping it in motion is the best
+place in which to work, to play, and to sleep, when work and play are
+done and we rest until another day comes. Indoors we need all the air we
+can coax to come in through windows and doors. Fresh air purifies air
+that is stale and unwholesome from being shut up. Nobody is afraid,
+nowadays, to breathe night air! What a foolish notion it was that led
+people to close their bedroom windows at night. Clean air, in plenty,
+day and night, we need. Air and sunshine are the two best gifts of God.
+
+
+
+
+THE WORK OF THE WIND
+
+
+When the March wind comes blustering down the street, rudely dashing a
+cloud of dust in our faces, we are uncomfortable and out of patience. We
+duck our heads and cover our faces, but even then we are likely to get a
+cinder in one eye, to swallow germs by the dozens, and to get a gray
+coating of plain, harmless dust. We welcome the rain that lays the dust,
+or its feeble imitation, the water sprinkler, that brings us temporary
+relief.
+
+On the quietest day, even after a thorough sweeping and dusting of the
+library, you are able to write your name plainly on the film of dust
+that lies on the polished table. Take a book from the open shelves, and
+blow into the trough of its top. This is always dusty. Where does the
+dust come from? This is the house-keeper's riddle.
+
+The answer is not a hard one. I look out of my window on a street which
+is famous as the road Washington took on his retreat from White Plains
+to Trenton. It has always been the main thoroughfare between New York
+and Philadelphia, and now is the route that automobiles follow. A
+constant procession of vehicles passes my house, and to-day each one
+approaches in a cloud of dust. The air is gray with suspended particles
+of dirt. The wind carries the successive clouds, and they roll up
+against the houses like breakers on the beach. Windows and doors are
+loose enough to let dust sift in. When a door opens, the cloud enters
+and lights on rugs and carpets and curtains. Any ledge collects its
+share of dust. The beating of carpets and rugs disturbs the accumulated
+dust of many months.
+
+[Illustration: In this lonely Arizona desert the wind drifts the sand
+into dunes, just as it does on the toe of Cape Cod]
+
+[Illustration: The Grand Canyon of the Colorado shows on a magnificent
+scale the work of water in cutting away rock walls]
+
+The wind sweeps the ploughed field, and takes all the dust it can carry.
+It blows the finest top soil from our gardens into the street. It blows
+soil from other fields and gardens into ours, so the level of our land
+is not noticeably lowered. The wind strips the high land and drops its
+burden on lower levels. This is one of the big jobs the water has to do,
+and the wind is a valuable helper. To tear down the mountains and fill
+in the valleys is the great work of the two partners, wind and water.
+
+Dead, still air holds the finest dust, without letting it fall. The
+buoyancy of the particles overcomes their weight. We see them in a
+sunbeam, like shining points of precious metal, and watch them. A light
+breeze picks up bits of soil and litter, from the smallest up to a
+certain size and weight. If the velocity of the wind increases, its
+carrying power increases. It is able to carry bits that are larger and
+heavier. The following table is exact and interesting:
+
+                      _Velocity_      _Pressure_
+                      _in Miles_      _in Pounds_
+                      _per Hour_     _per Sq. Ft._
+
+  Light breeze              14                   1
+  Strong breeze             42                   9
+  Strong gale               70                  25
+  Hurricane                 84                  36
+
+The terrible paths of hurricanes are seen in forest countries. The trees
+are uprooted, as if a great roller had crushed them, throwing the tops
+all in one direction, and leaving the roots uncovered, and a sunken
+pocket where each tree stood. On a steep, rocky slope, the uprooting of
+scattered trees often loosens tons of rock, and sends the mass
+thundering down the mountain-side. Much more destruction may be
+accomplished by one brief tornado than by years of wear by ordinary
+breezes.
+
+The wind does much to help the waves in their patient beating on rocky
+shores. If the wind blows from the ocean and the tide is landward, the
+two forces combine, and the loose rocks are thrown against the solid
+beach with astonishing force. Even the gravel and the sharp sand are
+tools of great usefulness to the waves in grinding down the resisting
+shore. Up and back they are swept by the water, and going and coming
+they have their chance to scratch or strike a blow. Boulders on the
+beach become pockmarked by the constant sand-blast that plays upon them.
+The lower windows of exposed seaside houses are dimmed by the sand that
+picks away the smooth surface outside, making it ground glass by the
+same process used in the factory. Lighthouses have this difficulty in
+keeping their windows clear. The "lantern" itself is sometimes reached
+by the sand grains. That is the cupola in which burns the great light
+that warns vessels away from the rocks and tells the captain where he
+is.
+
+In the Far Western States the telegraph poles and fence posts are soon
+cut off at the ground by the flinty knives the wind carries. These are
+the grains of sand that are blown along just above the ground. The trees
+are killed by having their bark girdled in this way. The sand-storms
+which in the orange and lemon region of California are called "Santa
+Anas" sometimes last two or three days, and damage the trees by piercing
+the tender bark with the needle-pointed sand.
+
+Wind-driven soil, gathered from the sides of bare hills and mountains,
+fills many valleys of China with a fine, hard-packed material called
+"loess." In some places it is hundreds of feet deep. The people dig into
+the side of a hill of this loess and carry out the diggings, making
+themselves homes, of many rooms, with windows, doors, and solid walls
+and floors, all in one solid piece, like the chambered house a mole
+makes underground in the middle of a field. So compact is the loess that
+there is no danger of a cave-in.
+
+The hills of sand piled up on the southern shore of Lake Michigan, and
+at Provincetown, at the toe of Cape Cod, are the work of the wind. On
+almost any sandy shore these "dunes" are common. The long slope is
+toward the beach that furnishes the sand. The wind does the building. Up
+the slope it climbs, then drops its burden, which slides to the bottom
+of an abrupt landward steep. There is a gradual movement inland if the
+strongest winds come from the water. The shifting of the dunes threatens
+to cover fertile land near them. In the desert regions, the border-land
+is always in danger of being taken back again, even though it has been
+reclaimed from the desert and cultivated for long years.
+
+Besides tearing down, carrying away, and building up again the fragments
+of the earth's crust, the wind does much that makes the earth a pleasant
+planet to live on. It drives the clouds over the land, bringing rains
+and snows and scattering them where they will bless the thirsty ground
+and feed the springs and brooks and rivers. It scatters the seeds of
+plants, and thus plants forests and prairies and lovely mountain slopes,
+making the wonderful wild gardens that men find when they first enter
+and explore a new region. The trade winds blow the warm air of the
+Tropics north and south, making the climate of the northern countries
+milder than it would otherwise be. Sea winds blow coolness over the land
+in summer, and cool lake breezes temper the inland regions. From the
+snow-capped mountains come the winds that refresh the hot, tired worker
+in the valleys.
+
+Everywhere the wind blows, the life-giving oxygen is carried. This is
+what we mean when we speak of fresh air. Stagnant air is as unwholesome
+as stagnant water. Constant moving purifies both. So we must give the
+wind credit for some of the greatest blessings that come into our lives.
+Light and warmth come from the sun. Pure water and pure air are gifts
+the bountiful earth provides. Without them there would be no life on the
+earth.
+
+
+
+
+RAIN IN SUMMER
+
+
+    How beautiful is the rain!
+    After the dust and heat,
+    In the broad and fiery street,
+    In the narrow lane,
+    How beautiful is the rain!
+
+    How it clatters along roofs,
+    Like the tramp of hoofs!
+    How it gushes and struggles out
+    From the throat of the overflowing spout!
+    Across the window-pane
+
+    It pours and pours;
+    And swift and wide,
+    With a muddy tide,
+    Like a river down the gutter roars
+    The rain, the welcome rain!
+
+    The sick man from his chamber looks
+    At the twisted brooks;
+    He can feel the cool
+    Breath of each little pool;
+    His fevered brain
+    Grows calm again,
+    And he breathes a blessing on the rain.
+
+                 --HENRY W. LONGFELLOW.
+
+
+
+
+WHAT BECOMES OF THE RAIN?
+
+
+The clouds that sail overhead are made of watery vapour. Sometimes they
+look like great masses of cotton-wool against the intense blue of the
+sky. Sometimes they are set like fleecy plumes high above the earth.
+Sometimes they hang like a sullen blanket of gray smoke, so low they
+almost touch the roofs of the houses. Indeed, they often rest on the
+ground and then we walk through a dense fog.
+
+In their various forms, clouds are like wet sponges, and when they are
+wrung dry they disappear--all their moisture falls upon the earth. When
+the air is warm, the water comes in the form of rain. If it is cold, the
+drops are frozen into hail, sleet, or snow.
+
+All of the water in the oceans, in the lakes and rivers, great and
+small, all over the earth, comes from one source, the clouds. In the
+course of a year enough rain and snow fall to cover the entire surface
+of the globe to a depth of forty inches. This quantity of water amounts
+to 34,480 barrels on every acre. What becomes of it all?
+
+We can easily understand that all the seas and the other bodies of water
+would simply add forty inches to their depth, and many would become
+larger, because the water would creep up on their gradually sloping
+shores. We have to account for the rain and the snow that fall upon the
+dry land and disappear.
+
+Go out after a drenching rainstorm and look for the answer to this
+question. The gullies along the street are full of muddy, running water.
+There are pools of standing water on level places, but on every slope
+the water is hurrying away. The ground is so sticky that wagons on
+country roads may mire to the hubs in the pasty earth. There is no use
+in trying to work in the garden or to mow the lawn. The sod is soft as a
+cushion, and the garden soil is water-soaked below the depth of a
+spading-fork.
+
+The sun comes out, warm and bright, and the flagstones of the sidewalk
+soon begin to steam like the wooden planks of the board walk. The sun is
+changing the surface water into steam which rises into the sky to form a
+part of another bank of clouds. The earth has soaked up quantities of
+the water that fell. If we followed the racing currents in the gullies
+we should find them pouring into sewer mains at various points, and from
+these underground pipes the water is conducted to some outlet like a
+river. All of the streams are swollen by the hundreds of brooks and
+rivulets that are carrying the surface water to the lowest level.
+
+[Illustration: Rain and wind are the sculptors that have carved these
+strange castles out of a rocky table]
+
+[Illustration: All the water in the seas, lakes, rivers, and springs
+came out of the clouds]
+
+So we can see some of the rainfall going back to the sky, some running
+off through rivulets to the sea, and some soaking into the ground. It
+will be interesting to follow this last portion as it gradually settles
+into the earth. The soil will hold a certain quantity, for it is made up
+of fine particles, all separated by air spaces, and it acts like a
+sponge. In seasons of drought and great heat the sun will draw this soil
+water back to the surface, by forming cracks in the earth, and fine,
+hair-like tubes, through which the vapour may easily rise. The gardener
+has to rake the surface of the beds frequently to stop up these channels
+by which the sun is stealing the precious moisture.
+
+The water that the surface soil cannot absorb sinks lower and lower into
+the ground. It finds no trouble to settle through layers of sand, for
+the particles do not fit closely together. It may come to a bed of clay
+which is far closer. Here progress is retarded. The water may
+accumulate, but finally it will get through, if the clay is not too
+closely packed. Again it may sink rapidly through thick beds of gravel
+or sand. Reaching another bed of clay which is stiffer by reason of the
+weight of the earth above it, the water may find that it cannot soak
+through. The only way to pass this clay barrier is to fill the basin,
+and to trickle over the edge, unless a place is found in the bottom
+where some looser substance offers a passage. Let us suppose that a
+concave clay basin of considerable depth is filled with water-soaked
+sand. At the very lowest point on the edge of this basin a stream will
+slowly trickle out, and will continue to flow, as long as water from
+above keeps the bowl full.
+
+It is not uncommon to find on hillsides, in many regions, little brooks
+whose beginnings are traceable to springs that gush out of the ground.
+The spring fills a little basin, the overflow of which is the brook. If
+the source of this spring could be traced underground, we might easily
+follow it along some loose rock formation until we come to a clay basin
+like the one described above. We might have to go down quite a distance
+and then up again to reach the level of this supply, but the level of
+the water at the mouth of the spring can never be higher than the level
+of the water in the underground supply basin.
+
+Often in hot summers springs "go dry." The level of water in the supply
+basin has fallen below the level of the spring. We must wait until
+rainfall has added to the depth of water in the basin before we can
+expect any flow into the pool which marks the place where the brook
+begins.
+
+Suppose we had no beds of clay, but only sand and gravel under the
+surface soil. We should then expect the water to sink through this loose
+material without hindrance, and, finding its way out of the ground, to
+flow directly into the various branches of the main river system of our
+region. After a long rain we should have the streams flooded for a few
+days, then dry weather and the streams all low, many of them entirely
+dry until the next rainstorm.
+
+Instead of this, the soil to a great depth is stored with water which
+cannot get away, except by the slow process by which the springs draw
+it off. This explains the steady flow of rivers. What should we do for
+wells if it were not for the water basins that lie below the surface? A
+shallow well may go dry. Its owner digs deeper, and strikes a lower
+"vein" of water that gives a more generous supply. In the regions of the
+country where the drift soil, left by the great ice-sheet, lies deepest,
+the glacial boulder clay is very far down. The surface water, settling
+from one level to another, finally reaches the bottom of the drift.
+Wells have to be deep that reach this water bed.
+
+The water follows the slope of this bed and is drained into the ocean,
+sometimes by subterranean channels, because the bed of the nearest river
+is on a much higher level. So we must not think that the springs contain
+only the water that feeds the rivers. They contain more.
+
+The layers of clay at different levels, from the surface down to the
+bottom of the drift, form water basins and make it possible for people
+to obtain a water supply without the expense of digging deep wells. The
+clayey subsoil, only a few feet below the surface, checks the downward
+course of the water, so that the sun can gradually draw it back, and
+keep a supply where plant roots can get it. The vapour rising keeps the
+air humid, and furnishes the dew that keeps all plant life comfortable
+and happy even through the hot summer months.
+
+Under the drift lie layers of stratified rock, and under these are the
+granites and other fire-formed rocks, the beginning of those rock masses
+which form the solid bulk of the globe. We know little about the core of
+the earth, but the granites that are exposed in mountain ridges are
+found to have a great capacity for absorbing water, so it is not
+unlikely that much surface water soaks into the rock foundations and is
+never drained away into the sea.
+
+The water in our wells is often hard. It becomes so by passing through
+strata of soil and rock made, in part, at least, of limestone, which is
+readily dissolved by water which contains some acid. Soil water absorbs
+acids from the decaying vegetation,--the dead leaves and roots of
+plants. Rain water is soft, and so is the water in ponds that have muddy
+basins, destitute of lime. Water in the springs and wells of the
+Mid-Western States is "hard" because it percolates through limestone
+material. In many parts of this country the well water is "soft,"
+because of the scarcity of limestone in the soil.
+
+I have seen springs around which the plants and the pebbles were coated
+with an incrustation of lime. "Petrified moss" is the name given to the
+plants thus turned to stone. The reason for this deposit is clear.
+Underground water is often subjected to great pressure, and at this time
+it is able to dissolve much more of any mineral substance than under
+ordinary conditions. When the pressure is released, the water is unable
+to hold in solution the quantity of mineral it contains; therefore, as
+it flows out through the mouth of the spring, the burden of mineral is
+laid down. The plants coated with the lime gradually decay, but their
+forms are preserved.
+
+There are springs the water of which comes out burdened with iron, which
+is deposited as a yellowish or red mineral on objects over which it
+flows. Ponds fed by these springs accumulate deposits of the mineral in
+the muddy bottoms. Some of the most valuable deposits of iron ore have
+accumulated in bogs fed by iron-impregnated spring water. In a similar
+way lime deposits called marl or chalk are made.
+
+
+
+
+THE SOIL IN FIELDS AND GARDENS
+
+
+City and country teachers are expected to teach classes about the
+formation and cultivation of soil. It is surprising how much of the
+needed materials can be brought in by the children, even in the cities.
+The beginning is a flowering plant growing in a pot. A window box is a
+small garden. A garden plot is a miniature farm.
+
+_Materials to collect for study indoors._ A few pieces of different
+kinds of rock: Granite, sandstone, slate; gravelly fragments of each,
+and finer sand. Pebbles from brooks and seashore. Samples of clays of
+different colors, and sands. Samples of sandy and clay soils, black pond
+muck, peat and coal. Rock fossils. A box of moist earth with earthworms
+in it. _Keep it moist._ A piece of sod, and a red clover plant with the
+soil clinging to its roots.
+
+_What is soil?_ It is the surface layer of the earth's crust, sometimes
+too shallow on the rocks to plough, sometimes much deeper. Under deep
+soil lies the "subsoil," usually hard and rarely ploughed.
+
+_What is soil made of?_ Ground rock materials and decayed remains of
+animal and plant life. By slow decay the soil becomes rich food for the
+growing of new plants. Wild land grows up to weeds and finally to
+forests. The soil in fields and gardens is cultivated to make it
+fertile. Plants take fertility from the soil. To maintain the same
+richness, plant food must be put back into the soil. This is done by
+deep tillage, and by mixing in with the soil manures, green crops, like
+clover, and commercial fertilizers.
+
+_Plants must be made comfortable, and must be fed._ Few plants are
+comfortable in sand. It gets hot, it lets water through, and it shifts
+in wind and is a poor anchor for roots. Clay is so stiff that water
+cannot easily permeate it; roots have the same trouble to penetrate it
+and get at the food it is rich in. Air cannot get in.
+
+Sand mixed with clay makes a mellow soil, which lets water and air pass
+freely through. The roots are more comfortable, and the tiny root hairs
+can reach the particles of both kinds of mineral food. But the needful
+third element is decaying plant and animal substances, called "humus."
+These enrich the soil, but they do a more important thing: their decay
+hastens the release of plant food from the earthy part of the soil, and
+they add to it a sticky element which has a wonderful power to attract
+and hold the water that soaks into the earth.
+
+_What is the best garden soil?_ A mixture of sand, clay, and humus is
+called "loam." If sand predominates, it is a sandy loam--warm, mellow
+soil. If clay predominates, we have a clay loam--a heavy, rich, but
+cool soil. All gradations between the two extremes are suited to the
+needs of crops, from the melons on sandy soil, to celery that prefers
+deep, cool soil, and cranberries that demand muck--just old humus.
+
+_How do plant roots feed in soil?_ By means of delicate root hairs which
+come into contact with particles of soil around which a film of soil
+water clings. This fluid dissolves the food, and the root absorbs the
+fluid. Plants can take no food in solid form. Hence it is of the
+greatest importance to have the soil pulverized and spongy, able to
+absorb and hold the greatest amount of water. The moisture-coated soil
+particles must have air-spaces between them. Air is as necessary to the
+roots as to the tops of growing plants.
+
+_Why does the farmer plough and harrow and roll the land?_ To pulverize
+the soil; to mellow and lighten it; to mix in thoroughly the manure he
+has spread on it, and to reach, if he can, the deeper layers that have
+plant food which the roots of his crops have not yet touched. Killing
+weeds is but a minor business, compared with tillage.
+
+Later, ploughing or cultivating the surface lightly not only destroys
+the weeds, but it checks the loss of water by evaporation from the
+cracks that form in dry weather. Raking the garden once a day in dry
+weather does more good than watering it. The "dust mulch" acts as a cool
+sunguard over the roots.
+
+_The process of soil-making._ If the man chopping wood in the Yosemite
+Valley looks about him he can see the soil-making forces at work on a
+grand scale. The bald, steep front of El Capitan is of the hardest
+granite, but it is slowly crumbling, and its fragments are accumulating
+at the bottom of the long slope. Rain and snow fill all crevices in the
+rocks. Frost is a wonderful force in widening these cracks, for water
+expands when it freezes. The loosened rock masses plough their way down
+the steep, gathering, as they go, increasing power to tear away any
+rocks in their path.
+
+Wind blows finer rock fragments along, and they lodge in cracks. Fine
+dust and the seeds of plants are lodged there. The rocky slopes of the
+Yosemite Valley are all more or less covered with trees and shrubs that
+have come from wind-sown seeds. These plants thrust their roots deeper
+each year into the rock crevices. The feeding tips of roots secrete
+acids that eat away lime and other substances that occur in rocks. Dead
+leaves and other discarded portions of the trees rot about their roots,
+and form soil of increasing depth. The largest trees grow on the rocky
+soil deposited at the base of the slope. The tree's roots prevent the
+river from carrying it off.
+
+When granite crumbles, its different mineral elements are separated.
+Clear, glassy particles of quartz we call sand. Dark particles of
+feldspar become clay, and may harden into slate. Sand may become
+sandstone. Exposed slate and sandstone are crumbled by exposure to wind
+and frost and moving water, and are deposited again as sand-bars and
+beds of clay.
+
+The most interesting phase of soil study is the discovery of what a work
+the humble earthworm does in mellowing and enriching the soil.
+
+
+
+
+THE WORK OF EARTHWORMS
+
+
+The farmer and the gardener should expect very poor crops if they
+planted seed without first ploughing or spading the soil. Next, its fine
+particles must be separated by the breaking of the hard clods. A wise
+man ploughs heavy soil in the fall. It is caked into great clods which
+crumble before planting time. The water in the clods freezes in winter.
+The expansion due to freezing makes this soil water a force that
+separates the fine particles. So the frost works for the farmer.
+
+Just under the surface of the soil lives a host of workers which are our
+patient friends. They work for their living, and are perhaps unconscious
+of the fact that they are constantly increasing the fertility of the
+soil. They are the earthworms, also called fishworms, which are
+distributed all over the world. They are not generally known to farmers
+and gardeners as friendly, useful creatures, and their services are
+rarely noticed. We see robins pulling them out of the ground, and we are
+likely to think the birds are ridding us of a garden pest. What we need
+is to use our eyes, and to read the wonderful discoveries recorded in a
+book called "Vegetable Mould and Earthworms," written by Charles
+Darwin.
+
+The benefits of ploughing and spading are the loosening and pulverizing
+of the packed earth; the mixing of dead leaves and other vegetation on
+and near the surface with the more solid earth farther down; the letting
+in of water and air; and the checking of loss of water through cracks
+the sun forms by baking the soil dry.
+
+The earthworm is a creature of the dark. It cannot see, but it is
+sufficiently sensitive to light to avoid the sun, the rays of which
+would shrivel up its moist skin. Having no lungs or gills, the worm uses
+the skin as the breathing organ; and it must be kept moist in order to
+serve its important use. This is why earthworms are never seen above
+ground except on rainy days, and never in the top soil if it has become
+dry. In seasons of little rain, they go down where the earth is moist,
+and venture to the surface only at night, when dew makes their coming up
+possible.
+
+Earthworms have no teeth, but they have a long snout that protrudes
+beyond the mouth. Their food is found on and in the surface soil. They
+will eat scraps of meat by sucking the juices, and scrape off the pulp
+of leaves and root vegetables in much the same way. Much of their
+subsistence is upon organic matter that can be extracted from the soil.
+Quantities of earth are swallowed. It is rare that an earthworm is dug
+up that does not show earth pellets somewhere on their way through the
+long digestive canal. The rich juices of plant substance are absorbed
+from these pellets as they pass through the body.
+
+Earthworms explore the surface of the soil by night, and pick up what
+they can find of fresh food. Nowhere have I heard of them as a nuisance
+in gardens, but they eagerly feed on bits of meat, especially fat, and
+on fresh leaves. They drag all such victuals into their burrows, and
+begin the digestion of the food by pouring on it from their mouths a
+secretion somewhat like pancreatic juice.
+
+The worms honeycomb the earth with their burrows, which are long,
+winding tubes. In dry or cold weather these burrows may reach eight feet
+under ground. They run obliquely, as a rule, from the surface, and are
+lined with a layer of the smooth soil, like soft paste, cast from the
+body. The lining being spread, the burrow fits the worm's body closely.
+This enables it to pass quickly from one end to the other, though it
+must wriggle backward or forward without turning around.
+
+At the lower end of the burrow, an enlarged chamber is found, where
+hibernating worms coil and sleep together in winter. At the top, a
+lining of dead leaves extends downward for a few inches, and in day time
+a plug of the same material is the outside door. At night the worm comes
+to the surface, and casts out the pellets of earth swallowed. The burrow
+grows in length by the amount of earth scraped off by the long snout
+and swallowed. The daily amount of excavation done is fairly estimated
+by the castings observed each morning on the surface.
+
+One earthworm's work for the farmer is not very much, but consider how
+many are at work, and what each one is doing. It is boring holes through
+the solid earth, and letting in the surface water and the air. It is
+carrying the lower soil up to the surface, often the stubborn subsoil,
+that no plough could reach. It is burying and thus hastening the decay
+of plant fibre, which lightens heavy soil and makes it rich because it
+is porous. Moreover, the earthworms are doing over and over again this
+work of fining and turning over the soil, which the plough does but
+seldom.
+
+By the continuous carrying up of their castings, the earthworms
+gradually bury manures spread on the surface. The collapse of their
+burrows and the making of new ones keep the soil constantly in motion.
+The particles are being loosened and brought into contact with the soil
+water, that dissolves, and thus frees for the use of feeding roots, the
+plant food stored in the rock particles that compose the mineral part of
+the soil.
+
+The weight of earth brought to the surface by worms in the course of a
+year has been carefully estimated. Darwin gives seven to eighteen tons
+per acre as the lowest and highest reports, based on careful collecting
+of castings by four observers, working on small areas of totally
+different soils. In England, earthworms have done a great deal more
+toward burying boulders and ancient ruins than any other agency. They
+eagerly burrow under heavy objects, the weight of which causes them to
+crush the honeycombed earth. Undiscouraged, the earthworms repeat their
+work.
+
+"Long before man existed, the land was regularly ploughed, and continues
+still to be ploughed by earthworms. It may be doubted whether there are
+many other animals which have played so important a part in the history
+of the world as have these lowly organized creatures."
+
+After years of study, Charles Darwin came to this conclusion. The more
+we study the lives of these earth-consuming creatures, the more fully do
+we believe what the great nature student said. The fertile soil is made
+of rock meal and decayed leaves and roots. Only recently have ploughs
+been invented. But the great forest crops have grown in soil made mellow
+by the earthworm's ploughing.
+
+
+
+
+QUIET FORCES THAT DESTROY ROCKS
+
+
+Wind and water are the blustering active agents we see at work tearing
+down rocks and carrying away their particles. They do the most of this
+work of levelling the land; but there are quiet forces at work which
+might not attract our attention at all, and yet, without their help,
+wind and running water would not accomplish half the work for which they
+take the credit.
+
+The air contains certain destructive gases which by their chemical
+action separate the particles of the hardest rocks, causing them to
+crumble. Now the wind blows away these crumbling particles, and the
+solid unchanged rock beneath is again exposed to the crumbling agencies.
+
+The changes in temperature between day and night cause rocks to contract
+and expand, and these changes put a strain upon the mineral particles
+that compose them. Much scaling of rock surfaces is due to these causes.
+Building a fire on top of a rock, and then dashing water upon the heated
+mass, shatters it in many directions. This process merely intensifies
+the effect produced by the mild changes of winter and summer. Water is
+present in most rocks, in surprising quantities, often filling the
+spaces in porous rocks like sandstones.
+
+When winter brings the temperature down to the freezing point, the water
+near the surface of the rock first feels it. Ice forms, and every
+particle of water is swollen by the change. A strain is put upon the
+mineral particles against which the particles of ice crowd for more
+room. Frost is a very powerful agent in the crumbling of rocks, as well
+as of stubborn clods of earth. In warm climates, and in desert regions
+where there is little moisture in the rocks, this destructive action of
+freezing water is not known. In cold countries, and in high altitudes,
+where the air is heavy with moisture, its greatest work is done.
+
+Some kinds of rock decay when they become dry, and resist crumbling
+better when they absorb a certain amount of moisture. Alternate wetting
+and drying is destructive to certain rocks.
+
+One of the unnoticed agents of rock decay is the action of lowly plants.
+Mosses grow upon the faces of rocks, thrusting their tiny root processes
+into pits they dig deeper by means of acids secreted by the delicate
+tips. You have seen shaded green patches of lichens, like little rugs,
+of different shapes, spread on the surface of rocks. But you cannot see
+so well the work these growths are doing in etching away the surface,
+and feeding upon the decaying mineral substance.
+
+Mosses and lichens do a mighty work, with the help of water, in
+reducing rocks to their original elements, and thus forming soil. No
+plants but lichens and mosses can grow on the bare faces of rocks. As
+their root-like processes lengthen and go deeper into the rock face,
+particles are pried off, and the under-substance is attacked. Higher
+plants then find a footing. Have you not seen little trees growing on a
+patch of moss which gets its food from the air and the rock to which it
+clings? The spongy moss cushion soaks up the rain and holds it against
+the rock face. A streak of iron in the rock may cause the water to
+follow and rust it out, leaving a distinct crevice. Now the roots of any
+plant that happens to be growing on the moss may find a foot-hold in the
+crack. Streaks of lime in a rock readily absorb water, which gradually
+dissolves and absorbs its particles, inviting the roots to enter these
+new passages and feed upon the disintegrating minerals. Dead leaves
+decay, and the acids the trickling water absorbs from them are
+especially active in disintegrating lime rocks.
+
+From such small beginnings has resulted the shattering of great rock
+masses by the growth of plants upon them. Tree roots that grow in rock
+crevices exert a power that is irresistible. The roots of smaller plants
+do the same great work in a quieter way.
+
+When a hurricane or a flood tears down the mountain-side, sweeping
+everything before it, trees, torn out by the roots, drag great masses
+of rock and soil into the air, and fling them down the slope. Wind and
+water thus finish the destruction which the humble mosses and lichens
+began. What seemed an impregnable fortress of granite has crumbled into
+fragments. Its particles are reduced to dust, or are on the way to this
+condition. The plant food locked up in granite boulders becomes
+available to hungry roots. Forests, grain-fields, and meadows cover the
+work of destructive agencies with a mantle of green.
+
+
+
+
+HOW ROCKS ARE MADE
+
+
+The granite shaft is made out of the original substance of the earth's
+crust. Its minerals are the elements out of which all of the rock masses
+of the earth are formed, no matter how different they look from granite.
+Sandstone is made of particles of quartz. Clay and slate are made out of
+feldspar and mica. Iron ore comes from the hornblende in granite. The
+mineral particles, reassembled in different proportions, form all of the
+different rocks that are known.
+
+Here in my hand is a piece of pudding-stone. It is made of pebbles of
+different sizes, each made of different coloured minerals. The pebbles
+are cemented together with a paste that has hardened into stone. This
+kind of rock the geologists call _conglomerate_. Pudding-stone is the
+common name, for the pebbles in the pasty matrix certainly do suggest
+the currants and the raisins that are sprinkled through a Christmas
+pudding.
+
+Under the seashores there are forming to-day thick beds of sand. The
+rivers bring the rock material down from the hills, and it is sorted and
+laid down. The moving water drops the heaviest particles near shore, and
+carries the finer ones farther out before letting them fall.
+
+[Illustration: The town of Cripple Creek, Colorado, which has grown up
+like magic since 1891, covers the richest gold and silver mines in the
+world]
+
+[Illustration: The level valley is filled up with fine rock flour washed
+from the sides of the neighboring mountains]
+
+The hard water, that comes through limestone rocks, adds lime in
+solution to the ocean water. All the shellfish of the sea, and the
+creatures with bony skeletons, take in the bone-building, shell-making
+lime with their food. Generations of these inhabitants of the sea have
+died, and their shells and bones have accumulated and been transformed
+into thick beds of limestone on the ocean floor. This is going on
+to-day; but the limestone does not accumulate as rapidly as when the
+ocean teemed with shell-bearing creatures of gigantic size. Of these we
+shall speak in another chapter.
+
+The fine dust that is blown into the ocean from the land, and that makes
+river water muddy, accumulates on the sea bottom as banks of mud, which
+by the burden of later deposits is converted into clay. Sandstone is but
+the compressed sand-bank.
+
+In the study of mountains, geologists have discovered that old seashores
+were thrown up into the first great ridges that form the backbone of a
+mountain system. The Rocky Mountains, and the Appalachian system on the
+east, were made out of thick strata of rocks that had been formed by
+accumulations of mud and sand--the washings of the land--on the opposite
+shores of a great mid-continental sea, that stretched from the crest of
+one great mountain system across to the other, and north and south from
+the Laurentian Hills to the Gulf of Mexico. The great weight of the
+accumulating layers of rock materials on one side, and the wasted land
+surfaces on the other, made the sea border a line of greatest weakness
+in the crust of the earth. The shrinking of the globe underneath caused
+the break; mashing and folding followed, throwing the ridge above
+sea-level, and making dry land out of rock waste which had been
+accumulating, perhaps for millions of years, under the sea. The
+wrinkling of the earth's crust was the result of crushing forces which
+produced tremendous heat.
+
+Streams of lava sprang out through the fissures and poured streams of
+melted rock down the sides of the fold, quite burying, in many places,
+the layers of limestone, sandstone, and clay. Between the strata of
+water-formed rocks there were often created chimney-like openings, into
+which molten rock from below was forced, forming, when cool, veins and
+dikes of rock material, specimens of the substance of the earth's
+interior.
+
+Tremendous pressure and heat, acting upon stratified rocks saturated
+with water transform them into very different kinds of rock. Limestone,
+subjected to these forces, is changed into marble. Clays are transformed
+into slates. Sandstone is changed into quartzite, the sand grains being
+melted so as to become no longer visible to the naked eye. The
+anthracite coal of the Pennsylvania mountains is the result of heat and
+pressure acting upon soft coal. Associated with these beds of hard coal
+are beds of black lead, or graphite, the substance used in making "lead"
+pencils. We believe that the same forces that operated to transform clay
+rocks into slate, and limestone into marble, transformed soft coal into
+hard, and hard coal into graphite, in the days when the earth was young.
+
+The word _sedimentary_ is applied to rocks which were originally laid
+down under water, as sediment, brought by running water, or by wind, or
+by the decay of organic substances. _Stratified_ rocks are those which
+are arranged in layers. Sedimentary rocks will fall into this class.
+_Aqueous_ rocks are those which are formed under water. Most of the
+stratified and sedimentary rocks, but not all, may be included under
+this term. Rocks that are made out of fragments of other rocks torn down
+by the agencies of erosion are called _fragmental_. Wind, water, and ice
+are the three great agencies that wear away the land, bring rock
+fragments long distances, and deposit them where aqueous rocks are being
+formed. Volcanic eruptions bring material from the earth's interior.
+This material ranges all the way from huge boulders to the finest
+impalpable dust, called volcanic ashes. Rivers of ice called glaciers
+crowd against their banks, loosening rock masses and carrying away
+fragments of all sizes, in their progress down the valley. Brooks and
+rivers carry the pebbles and the larger rock masses they are able to
+loosen from their walls and beds, and grind them smooth as they move
+along toward lower levels.
+
+The air itself causes rocks to crumble; percolating water robs them of
+their soluble salts, reducing even solid granite to a loose mass of
+quartz grains and clay. Plants and animals absorb as food the mineral
+substances of rocks, when they are dissolved in water. They transform
+these food elements into their own body substance, and finally give back
+their dead bodies, the mineral substances of which are freed by decay to
+return to the earth, and become elements of rock again.
+
+The decay of rock is well shown by the materials that accumulate at the
+base of a cliff. Angular fragments of all sizes, but all more or less
+flattened, come from strata of shaly rock, that can be seen jutting out
+far above. A great deal of this sort of material is found mingled with
+the soil of the Northeastern States. Round pebbles in pudding-stone have
+been formed in brook beds and deposited on beaches where they have
+become caked in mud and finally consolidated into rock. If the beach
+chanced to be sandy instead of muddy, a matrix of sandy paste holds the
+larger pebbles in place. Limestone paste cements together the pebbles of
+limestone conglomerates.
+
+In St. Augustine many of the houses are built of coquina rock, a mass of
+broken shells which have become cemented together by lime mud, derived
+from their own decay. On the slopes of volcanoes, rock fragments of all
+kinds are cemented together by the flowing lava. So we see that there
+are pudding-stones of many kinds to be found. If some solvent acid is
+present in the water that percolates through these rocks it may soften
+the cement and thus free the pebbles, reducing the conglomerate again to
+a mere heap of shell fragments, or gravel, or rounded pebbles.
+
+The story of rock formation tells how fire and water, and the two
+combined, have made, and made over, again and again, the substance of
+the earth's crust. Chemical and physical changes constantly tear down
+some portions of the earth to build up others. The constant, combined
+effort of wind and water is to level the earth and fill up the ocean
+bed. Rocks are constantly being formed; the changes that have been going
+on since the world began are still in progress. We can see them all
+about us on any and every day of our lives.
+
+
+
+
+GETTING ACQUAINTED WITH A RIVER
+
+
+I have two friends whose childhood was spent in a home on the banks of a
+noble eastern river. Their father taught the boy and the girl to row a
+boat, and later each learned the more difficult art of managing a canoe.
+On holidays they enjoyed no pleasure so much as a picnic on the
+river-bank at some point that could be reached by rowing. As they grew
+older, longer trips were planned, and the river was explored as far as
+it was navigable by boat or canoe. Last summer when vacation came, these
+two carried out a long-cherished plan to find the beginning of the
+river--to follow it to its source. So they left home, and canoed
+up-stream, until the stream became a brook, so shallow they could go no
+farther. Then they followed it on foot--wading, climbing, making little
+d�tours, but never losing the little river. At last they came to the
+beginning of it--a tiny rivulet trickled out of the side of a hill,
+filling a wooden keg that formed a basin, where thirsty passers-by could
+stoop and drink. They decided to mark the spring, so that people who
+found it later, and were refreshed by its clear water, might know that
+here was born the greatest river of a great state. But they were not the
+original discoverers. Above the spring, a board was nailed to a tree,
+saying that this is the headwater of the river with the beautiful Indian
+name, Susquehanna.
+
+It was a dry summer, and the overflow of the basin was almost all drunk
+up by the thirsty ground. They could scarcely follow it, except by the
+groove cut by the rivulet in seasons when the flow was greater. They
+followed the runaway brook, through the grass roots, that almost hid it.
+As the ground grew steeper, it hurried faster. Soon it gathered the
+water of other springs, which hurried toward it in small rivulets,
+because its level was lower. Water always seeks the lowest level it can
+find. Sometimes marshy spots were reached where water stood in the holes
+made by the feet of cattle that came there to drink. The water was
+muddy, and seemed to stand still. But it was settling steadily, and at
+one side the little river was found, flowing away with the water it drew
+from the swampy, springy ground. All the mud was gone, now; the water
+was clear. It flowed in a bed with a stony floor, and there were rough
+steps where the water fell down in little sheets, forming a waterfall,
+the first of many that make this river beautiful in the upper half of
+its course. To get from the high level of that hillside spring to the
+low level of the sea, the water has to make a fall of twenty-three
+hundred feet, but it makes the descent gradually. It could not climb
+over anything, but always found a way to get around the rocks and hills
+that stood in its way. When the flat marsh land interfered, the water
+poured in and overflowed the basin at the lowest margin.
+
+In the rocky ground the two explorers found that the stream had widened
+its channel by entering a narrow crevice and wearing away its walls. The
+continual washing of the water wears away stone. Rocks are softened by
+being wet. Streaks of iron in the hardest granite will rust out and let
+the water in. Then the lime in rocks is easily dissolved. Every dead
+leaf the river carried along added an acid to the water, and this made
+easier the process of dissolving the limestone.
+
+Every crumbling rock gives the river tools that it uses like hammer and
+chisel and sandpaper to smooth all the uneven surfaces in its bed, to
+move stumbling blocks, and to dig the bed deeper and wider. The steeper
+the slope is, the faster the stream flows, and the larger the rocks it
+can carry. Rocks loosened from the stream bed are rolled along by the
+current. Then bang! against the rocks that are not loose, and often they
+are able to break them loose. The fine sand is swept along, and its
+sharp points strike like steel needles, and do a great work in polishing
+roughness and loosening small particles from the stream bed. The bigger
+pebbles of the stream have banged against the rock walls, with the same
+effect, smoothing away unevenness and pounding fragments loose, rolling
+against one another, and getting their own rough corners worn away.
+
+The makers of stone marbles learned their business from a brook. They
+cut the stone into cubical blocks, and throw them into troughs, into
+which is poured a stream of running water. The blocks are kept in
+motion, and the grinding makes each block help the rest to grind off the
+eight corners and the twelve ridges of each one. The water becomes muddy
+with the fine particles, just as the drip from a grindstone becomes
+unclean when an axe is ground. Pretty soon all the blocks in the trough
+are changed into globes--the marbles that children buy at the shops when
+marble season comes around.
+
+I suppose if the troughs are not watched and emptied in time, the
+marbles would gradually be ground down to the size of peas, then to the
+size of small bird shot, and finally they would escape as muddy water
+and fine sand grains.
+
+Sure it is that the sandy shores that line most rivers are the remnants
+of hard rocks that have been torn out and ground up by the action of the
+current.
+
+Not very many miles from its first waterfall the stream had grown so
+large that my two friends knew that they would soon find their canoes.
+The plan now was to float down the curious, winding river and to learn,
+if the river and the banks could tell them, just why the course was so
+crooked on the map. They came into a broad, level valley where streams
+met them, coming out of deep clefts between the hills they were leaving
+behind them. The banks were pebbly, but blackened with slimy mud that
+made the water murky. The current swerved from one side to the other,
+sometimes quite close to the bank, where the river turned and formed a
+deep bend. On this side the bank was steep, the roots of plants and
+trees exposed. On the opposite side a muddy bank sloped gently out into
+the stream. Here building up was going on, to offset the tearing down.
+
+The sharp bends are made sharper, once the current is deflected from the
+middle of the stream to one side. At length the loops bend on each other
+and come so near together that the current breaks through, leaving a
+semicircular bayou of still water, and the river's course straightened
+at that place. It must have been in a spring flood that this cut-off was
+made, and, the break once made was easily widened, for the soil is fine
+mud which, when soaked, crumbles and dissolves into muddy water.
+
+Stately and slow that river moves down to the bay, into which it empties
+its load. The rain that falls on hundreds of square miles of territory
+flows into the streams that feed this trunk. The little spring that is
+the headwater of the system is but one of many pockets in the hillsides
+that hold the water that soaks into the ground and give it out by slow
+degrees. Surface water after a rain flows quickly into the streams. It
+is the springs that hold back their supply and keep the rivers from
+running dry in hot weather.
+
+Do they feel now that they know their river? Are they ready to leave it,
+and explore some other? Indeed, no. They are barely introduced to it.
+All kinds of rivers are shown by the different parts of this one. It is
+a river of the mountains and of the lowland. It flows through woods and
+prairies, through rocky passes and reedy flats. It races impetuously in
+its youth, and plods sedately in later life. The trees and the other
+plants that shadow this stream, and live by its bounty, are very
+different in the upland and in the lowland. The scenery along this
+stream shows endless variety. Up yonder all is wild. Down here great
+bridges span the flood, boats of all kinds carry on the commerce between
+two neighbour cities. A great park comes down to the river-bank on one
+side. Canoes are thick as they can paddle on late summer afternoons.
+
+No one can ever really know a river well enough to feel that it is an
+old story. There is always something new it has to tell its friends. So
+my two explorers say, and they know far more about their friendly river
+than I do.
+
+
+
+
+THE WAYS OF RIVERS
+
+
+A canal is an artificial river, built to carry boats from one place to
+another. Its course is, as nearly as possible, a straight line between
+two points. A river, we all agree, is more beautiful than a canal, for
+it winds in graceful curves, in and out among the hills, its waters
+seeking the lowest level, always.
+
+No artist could lay out curves more beautiful than the river forms.
+These curves change from year to year, some slowly, some more rapidly.
+It is not hard to understand just why these changes take place.
+
+Some rivers are dangerous for boating at certain points. The current is
+strong, and there are eddies and whirlpools that have to be avoided, or
+the boat becomes unmanageable. People are drowned each season by
+trusting themselves to rivers the dangerous tricks of which they do not
+know. Deep holes are washed out of the bed of the stream by whirling
+eddies. The pot-holes of which people talk are deep, rounded cavities,
+ground out of the rocky stream-bed by the scouring of sand and loose
+stones driven by whirling eddies in shallow basins. Every year deepens
+each pot-hole until some change in the stream-bed shifts the eddy to
+another place.
+
+No stream finds its channel ready-made; it makes its own, and constantly
+changes it. The current swings to one side of the channel, lifting the
+loose sediment and grinding deeper the bed of the stream. The water lags
+on the opposite side, and sediment falls to the bottom. So the
+building-up of one side is going on at the same time that the
+tearing-down process is being carried on on the other. With the lowering
+of the bed the river swerves toward one bank, and a hollow is worn by
+slow degrees. The current swings into this hollow, and in passing out is
+thrown across the stream to the opposite bank. Here its force wears away
+another hollow; and so it zigzags down-stream. The deeper the hollows,
+the more curved becomes the course, if the general fall is but moderate.
+It is toward the lower courses of the stream that the winding becomes
+more noticeable. The sediment that is carried is deposited at the point
+where the current is least strong, so that while the outcurves become
+sharper by the tearing away of the stream's bank, the incurves become
+sharper by the building up of this bank.
+
+The Mississippi below Memphis is thrown into a wonderful series of
+curves by the erosion and the deposit caused by the current zigzagging
+back and forth from one bank to the other. Gradually the curves become
+loops. The river's current finally jumps across the meeting of the
+curves, and abandons the circular bend. It becomes a bayou or lagoon of
+still water, while the current flows on in the straightened channel.
+All rivers that flow through flat, swampy land show these intricate
+winding channels and many lagoons that have once been curves of the
+river.
+
+No one would ever mistake a river for a lake or any other body of water,
+yet rivers differ greatly in character. One tears its way along down its
+steep, rock-encumbered channel between walls that rise as vertical
+precipices on both sides. The roaming, angry waters are drawn into
+whirlpools in one place. They lie stagnant as if sulking in another,
+then leap boisterously over ledges of rock and are churned into creamy
+foam at the bottom. Outside the mountainous part of its course this same
+river flows broad and calm through a mud-banked channel, cut by
+tributary streams that draw in the water of low, sloping hills.
+
+The Missouri is such a wild mountain stream at its headwaters. We who
+have seen its muddy waters from Sioux City to St. Louis would hardly
+believe that its impetuous and picturesque youth could merge into an old
+age so comfortable and placid and commonplace.
+
+This thing is true of all rivers. They flow, gradually or suddenly, from
+higher to lower levels. To reach the lowest level as soon as possible is
+the end each river is striving toward. If it could, each river would cut
+its bed to this depth at the first stage of its course. Its tools are
+the rocks it carries, great and small. The force that uses these tools
+is the power of falling water, represented by the current of the stream.
+The upper part of a river such as the Missouri or Mississippi engages in
+a campaign of widening and deepening its channel, and carrying away
+quantities of sediment. The lower reaches of the stream flow through
+more level country; the current is checked, and a vast burden of
+sediment is laid down. Instead of tearing away its banks and bottom, the
+river fills up gradually with mud. The current meanders between banks of
+sediment over a bottom which becomes shallower year by year. The Rocky
+Mountains are being carried to the Gulf of Mexico. The commerce of the
+river is impeded by mountain d�bris deposited as mud-banks along the
+river's lower course.
+
+Many rivers are quiet and commonplace throughout their length. They flow
+between low, rounded hills, and are joined by quiet streams, that occupy
+the separating grooves between the hills. This is the oldest type of
+river. It has done its work. Rainfall and stream-flow have brought the
+level of the land nearly to the level of the stream. Very little more is
+left to be ground down and carried away. The landscape is beautiful, but
+it is no longer picturesque. Wind and water have smoothed away
+unevennesses. Trees and grass and other vegetation check erosion, and
+the river has little to do but to carry away the surface water that
+falls as rain.
+
+But suppose our river, flowing gently between its grassy banks, should
+feel some mighty power lifting it up, with all its neighbour hills and
+valleys, to form a wrinkle in the still unstable crust of the earth.
+Away off at the river's mouth the level may not have changed, or that
+region may have been depressed instead of elevated by the shrinking
+process. Suppose the great upheaval has not severed the upper from the
+lower courses of the stream. With tremendous force and speed, the
+current flows from the higher levels to the lower. The river in the
+highlands strikes hard to reach the level of its mouth. It grinds with
+all its might, and all its rocky tools, upon its bed. All the mud is
+scoured out, and then the underlying rocks are attacked. If these rocks
+are soft and easily worn away, the channel deepens rapidly. One after
+another the alternating layers are excavated, and the river flows in a
+canyon which deepens more and more. As the level is lowered, the current
+of the stream becomes slower and the cutting away of its bed less rapid.
+The stream is content to flow gently, for it has almost reached the old
+level, on which it flowed before the valley became a ridge or
+table-land.
+
+The rivers that flow in canyons have been thousands of years in carving
+out their channels, yet they are newer, geologically speaking, than the
+streams that drain the level prairie country. The earth has risen, and
+the canyons have been carved since the prairies became rolling, level
+ground.
+
+[Illustration: This little pond is a basin hollowed by the same glacier
+that scattered the stones and rounded the hills]
+
+[Illustration: Every stream is wearing away its banks, while trees and
+grass blades are holding on to the soil with all their roots]
+
+The Colorado River flows through a canyon with walls that in places
+present sheer vertical faces a mile in depth, and so smooth that no
+trail can be found by which to reach from top to bottom. The region has
+but slight erosion by wind, and practically none by rain. The local
+rainfall is very slight. So the river is the one force that has acted to
+cut down the rocks, and its force is all expended in the narrow area of
+its own bed. Had frequent rains been the rule on the Colorado plateau,
+the angles of the mesas would have been rounded into hills of the
+familiar kind so constantly a part of the landscape in the eastern half
+of the continent.
+
+The Colorado is an ancient river which has to carry away the store of
+moisture that comes from the Pacific Ocean and falls as snow on the high
+peaks of the Rocky Mountains. Similar river gorges with similar stories
+to tell are the Arkansas, the Platte, and the Yellowstone. All cut their
+channels unaided through regions of little rain.
+
+When the earth's crust is thrown up in mountain folds, and between them
+valleys are formed, the level of rivers is sometimes lowered and the
+rapidity of their flow is checked. A stream which has torn down its
+walls at a rapid rate becomes a sluggish water-course, its current
+clogged with sediment, which it has no power to carry farther. When such
+a river begins to build and obstruct its own waters it bars its progress
+and may form a lake as the outlet of its tributary streams. Many ancient
+rivers have been utterly changed and some obliterated by general
+movements of the earth's crust.
+
+
+
+
+THE STORY OF A POND
+
+
+Look out of the car window as you cross a flat stretch of new prairie
+country, and you see a great many little ponds of water dotting the
+green landscape. Forty years ago Iowa was a good place to see ponds of
+all shapes and sizes. The copious rainfall of the early spring gathered
+in the hollows of the land, and the stiff clay subsoil prevented the
+water from soaking quickly into the ground. The ponds might dry away
+during the hot, dry summer, leaving a baked clay basin, checked with an
+intricate system of cracks. Or if rains were frequent and heavy, they
+might keep full to the brim throughout the season.
+
+Tall bulrushes stood around the margins of the largest ponds, and
+water-lilies blossomed on the surface during the summer. The bass and
+the treble of the spring chorus were made by frogs and toads and little
+hylas, all of which resorted to the ponds to lay their eggs, in coiled
+ropes or spongy masses, according to their various family traditions. On
+many a spring night my zo�logy class and I have visited the squashy
+margins of these ponds, and, by the light of a lantern, seen singing
+toads and frogs sitting on bare hummocks of grass roots that stood
+above the water-line. The throat of each musician was puffed out into a
+bag about the size and shape of a small hen's egg; and all were singing
+for dear life, and making a din that was almost ear-splitting at close
+range. So great was the self-absorption of these singers that we could
+approach them, daze them with the light of the lantern, and capture any
+number of them with our long-handled nets before they noticed us. But it
+was not easy to persuade them to sing in captivity, no matter how many
+of the comforts of home we provided in the school aquariums. So, after
+some very interesting nature studies, we always carried them back and
+liberated them, where they could rejoin their kinsfolk and neighbours.
+
+It was when we were scraping the mud from our rubber boots that we
+realized the character of the bottoms of our prairie ponds. The slimy
+black deposit was made partly of the clay bottom, but largely of
+decaying roots and tops of water plants of various kinds. Whenever it
+rained or the wind blew hard, the bottom was stirred enough to make the
+water muddy; and on the quietest days a pail of pond water had a tinge
+of brown because there were always decaying leaves and other rubbish to
+stain its purity.
+
+The farmers drained the ponds as fast as they were able, carrying the
+water, by open ditches first, and later by underground tile drains, to
+lower levels. Finally these trunk drain pipes discharged the water into
+streams or lakes. To-day a large proportion of the pond areas of Iowa
+has disappeared; the hollow tile of terra-cotta has been the most
+efficient means of converting the waste land, covered by ponds, into
+fertile fields.
+
+But the ponds that have not been drained are smaller than they used to
+be, and are on the straight road to extinction. This process one can see
+at any time by visiting a pond. Every year a crop of reeds and a dozen
+other species of vigorous water plants dies at the top and adds the
+substance of their summer growth to the dust and other refuse that
+gathers in the bottom of the pond. Each spring roots and seeds send up
+another crop, if possible more vigorous than the last, and this top
+growth in turn dies and lies upon the bottom. The pond level varies with
+the rainfall of the years, but it averages a certain depth, from which
+something is each year subtracted by the accumulations of rotting
+vegetable matter in the bottom. Evaporation lowers the water-level,
+especially in hot, dry summers. From year to year the water plants draw
+in to form a smaller circle, the grassy meadow land encroaches on all
+sides. The end of the story is the filling up of the pond basin with the
+rotting substance of its own vegetation. This is what is happening to
+ponds and inland marshes by slow degrees. The tile drain pipes
+obliterate the pond in a single season. Nature is more deliberate. She
+may require a hundred years to fill up a single pond which the farmer
+can rid himself of by a few days of work and a few rods of tiling.
+
+
+
+
+THE RIDDLE OF THE LOST ROCKS
+
+
+Outside of my window two robins are building a nest in the crotch of a
+blossoming red maple tree. And just across the hedge, men are digging a
+big square hole in the ground--the cellar of our neighbour's new house.
+It looks now as if the robins would get their house built first, for
+they need but one room, and they do not trouble about a cellar. I shall
+watch both houses as they grow through the breezy March days.
+
+The brown sod was first torn up by a plough, which uncovered the red New
+Jersey soil. Two men, with a team hitched to a scraper, have carried
+load after load of the loose earth to a heap on the back of the lot,
+while two other men with pickaxes dug into the hard subsoil, loosening
+it, so that the scraper could scoop it up.
+
+This subsoil is heavy, like clay, and it breaks apart into hard clods.
+At the surface the men found a network of tree roots, about which the
+soil easily crumbled. Often I hear a sharp, metallic stroke, unlike the
+dull sound of the picks striking into the earth. The digger has struck a
+stone, and he must work around it, pry it up and lift it out of the way.
+A row of these stones is seen at one side of the cellar hole, ranged
+along the bank. They are all different in size and shape, and red with
+clay, so I can't tell what they are made of. But from this distance I
+see plainly that they are irregular in form and have no sharp corners.
+The soil strewn along the lot by the scraper is full of stones, mostly
+irregular, but some rounded; some are as big as your head, others grade
+down to the sizes of marbles.
+
+When I went down and examined this red earth, I found pebbles of all
+shapes and sizes, gravel in with the clay, and grains of sand. This
+rock-sprinkled soil in New Jersey is very much like soil which I know
+very well in Iowa; it looks different in colour, but those pebbles and
+rock fragments must be explained in the same way here as there.
+
+These are not native stones, the outcrop of near-by hillsides, but
+strangers in this region. The stones in Iowa soil are also imported.
+
+The prairie land of Iowa has not many big rocks on the surface, yet
+enough of them to make trouble. The man who was ploughing kept a sharp
+lookout, and swung his plough point away from a buried rock that showed
+above ground, lest it should break the steel blade. One of the farmer's
+jobs for the less busy season was to go out with sledge and dynamite
+sticks, and blast into fragments the buried boulders too large to move.
+Sometimes building a hot fire on the top of it, and throwing on water,
+would crack the stubborn "dornick" into pieces small enough to be loaded
+on stone-boats.
+
+I remember when the last giant boulder whose buried bulk scarcely showed
+at the surface, was fractured by dynamite. Its total weight proved to be
+many tons. We hauled the pieces to the great stone pile which furnished
+materials for walling the sides of a deep well and for laying the
+foundation of the new house. Yet for years stones have been
+accumulating, all of them turned out of the same farm, when pastures and
+swampy land came under the plough.
+
+Draw a line on the map from New York to St. Louis, and then turn
+northward a little and extend it to the Yellowstone Park. The
+boulder-strewn states lie north of this line, and are not found south of
+it, anywhere. Canada has boulders just like those of our Northern
+States. The same power scattered them over all of the vast northern half
+of North America and a large part of Europe.
+
+What explanation is there for this extensive distribution of unsorted
+d�bris?
+
+
+
+
+THE QUESTION ANSWERED
+
+
+The rocks tell their own story, partly, but not wholly. They told just
+enough to keep the early geologists guessing; and only very recently has
+the guessing come upon the truth.
+
+These things the rocks told:
+
+1. We have come from a distance.
+
+2. We have had our sharp corners worn off.
+
+3. Many of us have deep scratches on our sides.
+
+4. At various places we have been dumped in long ridges, mixed with much
+earth.
+
+5. A big boulder is often balanced on another one.
+
+The first thing the geologist noted was the fact that these boulders are
+strangers--that is, they are not the native rocks that outcrop on
+hillsides and on mountain slopes near where they are found. Far to the
+north are beds of rock from which this d�bris undoubtedly came. Could a
+flood have scattered them as they are found? No, for water sorts the
+rock d�bris it deposits, and it rounds and polishes rock fragments,
+instead of scratching and grooving them and leaving them angular, as
+these are.
+
+Professor Agassiz went to Switzerland and studied the glaciers. He found
+unsorted rock fragments where the glacier's nose melted, and let them
+fall. They were worn and scratched and grooved, by being frozen into the
+ice, and dragged over the rocky bed of the stream. The rocky walls of
+the valley were scored by the glacier's tools. Rounded domes of rock
+jutted out of the ground, in the paths of the ice streams, just like the
+granite outcrop in Central Park in New York, and many others in the
+region of scattered boulders.
+
+After long studies in Europe and in North America, Professor Agassiz
+declared his belief that a great ice-sheet once covered the northern
+half of both countries, rounding the hills, scooping out the valleys and
+lake basins, and scattering the boulders, gravel, and clay, as it
+gradually melted away.
+
+The belief of Professor Agassiz was not accepted at once, but further
+studies prove that he guessed the riddle of the boulders. The rich soil
+of the Northern States is the glacial drift--the mixture of rock
+fragments of all sizes with fine boulder clay, left by the gradual
+melting of the great ice-sheet as it retreated northward at the end of
+the "Glacial Epoch."
+
+
+
+
+GLACIERS AMONG THE ALPS
+
+
+Switzerland is a little country without any seacoast, mountainous, with
+steep, lofty peaks, and narrow valleys. The climate is cool and moist,
+and snow falls the year round on the mountain slopes. A snow-cap covers
+the lower peaks and ridges. Above the level of nine thousand feet the
+bare peaks rise into a dry atmosphere; but below this altitude, and
+above the six thousand-foot mark, lies the belt of greatest snowfall.
+Peaks between six and nine thousand feet high are buried under the
+Alpine snow-field, which adds thickness with each storm, and is drained
+away to feed the rushing mountain streams in the lower valleys.
+
+The snow that falls on the steep, smooth slope clings at first; but as
+the thickness and the weight of these snow banks increase, their hold on
+the slope weakens. They may slip off, at any moment. The village at the
+foot of the slope is in danger of being buried under a snow-slide, which
+people call an avalanche. "Challanche" is another name for it. The
+hunter on the snow-clad mountains dares not shout for fear that his
+voice, re�choing among the silent mountains, may start an avalanche on
+its deadly plunge into the valley.
+
+On the surface of the snow-field, light snow-flakes rest. Under them the
+snow is packed closer. Deeper down, the snow is granular, like pellets
+of ice; and still under this is ice, made of snow under pressure. The
+weight of the accumulated snow presses the underlying ice out into the
+valleys. These streams are the glaciers--rivers of ice.
+
+The glaciers of the Alps vary in length from five to fifteen miles, from
+one to three miles in width, and from two hundred to six hundred feet in
+thickness. They flow at the rate of from one to three feet a day, going
+faster on the steeper slopes.
+
+It is hard to believe that any substance as solid and brittle as ice can
+flow. Its movement is like that of stiff molasses, or wax, or pitch. The
+tremendous pressure of the snow-field pushes the mass of ice out into
+the valleys, and its own weight, combined with the constant pressure
+from behind, keeps it moving.
+
+The glacier's progress is hindered by the uneven walls and bed of the
+valley, and by any decrease in the slope of the bed. When a flat, broad
+area is reached, a lake of ice may be formed. These are not frequent in
+the Alps. The water near the banks and at the bottom of a river does not
+flow as swiftly as in the middle and at the surface of the stream. The
+flow of ice in a glacier is just so. Friction with the banks and bottom
+retards the ice while the middle parts go forward, melting under the
+strain, and freezing again. There is a constant readjusting of
+particles, which does not affect the solidity of the mass.
+
+The ice moulds itself over any unevenness in its bed if it cannot remove
+the obstruction. The drop which would cause a small waterfall in a
+river, makes a bend in the thick body of the ice river. Great cracks,
+called _crevasses_, are made at the surface, along the line of the bend.
+The width of the V-shaped openings depends upon the depth of the glacier
+and the sharpness of the bend that causes the breaks.
+
+Rocky ridges in the bed of the ice-stream may cause crevasses that run
+lengthwise of the glacier. Snow may fill these chasms or bridge them
+over. The hunter or the tourist who ventures on the glacier is in
+constant danger, unless he sees solid ice under him. Men rope themselves
+together in climbing over perilous places, so that if one slips into a
+crevasse his mates can save him.
+
+A glacier tears away and carries away quantities of rock and earth that
+form the walls of its bed. As the valley narrows, tremendous pressure
+crowds the ice against the sides, tearing trees out by the roots and
+causing rock masses to fall on the top of the glacier, or to be dragged
+along frozen solidly into its sides. The weight of the ice bears on the
+bed of the glacier, and its progress crowds irresistibly against all
+loose rock material. The glacier's tools are the rocks it carries frozen
+into its icy walls and bottom. These rocks rub against the walls,
+grinding off d�bris which is pushed or carried along. No matter how
+heavy the boulders are that fall in the way of the ice river, the ice
+carries them along. It cannot drop them as a river of water would do.
+Slowly they travel, and finally stop where the nose of the glacier melts
+and leaves all d�bris that the mountain stream, fed by the melting of
+the ice, cannot carry away.
+
+The bedrock under a glacier is scraped and ground and scored by the
+glacier's tools--the rock fragments frozen into the bottom of the ice.
+These rocks are worn away by constant grinding, just as a steel knife
+becomes thin and narrow by use. Scratches and scorings and polished
+surfaces are found in all rocks that pass one another in close contact.
+Its worn-out tools the glacier drops at the point where its ice melts.
+This great, unsorted mass of rock meal and coarser d�bris the stream is
+gradually scattering down the valley.
+
+The name "moraine" has been given to the earth rubbish a glacier
+collects and finally dumps. The _top moraine_ is at the surface of the
+ice. The _lateral moraines_, one at each side, are the d�bris gathered
+from the sides of the valley. The _ground moraine_ is what d�bris the
+ice pushes and drags along on the bottom. The _terminal moraine_ is the
+dumping-ground of this mass of material, where the ice river melts.
+
+Glaciers, like other rivers, often have tributary streams. A _median
+moraine_, seen as a dark streak running lengthwise on the surface of a
+glacier, means that two branch glaciers have united to form this one. Go
+back far enough and you will reach the place where the two streams come
+together. The two lateral moraines that join form the middle line of
+d�bris, the median moraine. Three ice-streams joined produce two top
+moraines. They locate the lateral moraines of the middle glacier.
+
+The surface of a glacier is often a mass of broken and rough ice,
+forming a series of pits and pinnacles that make crossing impossible.
+The sun melts the surface, forming pools and percolating streams of
+water, that honeycomb the mass. Underneath, the ice is tunnelled, and a
+rushing stream flows out under the end of the glacier. It is not clear,
+but black with mud, called _boulder clay_, or _till_, made of ground
+rock, and mixed with fragments of all shapes and sizes. This is the meal
+from the glacier's mill, dumped where the water can sift it.
+
+"Balanced rocks" are boulders, one upon another, that once lay on a
+glacier, and were left in this strange, unstable position when the
+supporting ice walls melted away from them. In Bronx Park in New York
+the "rocking stone" always attracts attention. The glacier that lodged
+it there, also rounded the granite dome in Central Park and scattered
+the rock-strewn boulder clay on Long Island. Doubtless in an earlier day
+the edges of this glacier were thrust out into the Atlantic, not far
+from the Great South Bay, and icebergs broke off and floated away.
+
+[Illustration: Potsdam sandstone showing ripple marks]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Glacial stri� on Lower Helderberg limestone]
+
+[Illustration: Glacial grooves in the South Meadow, Central Park, New
+York]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Mt. Tom, West 83d St., New York]
+
+Glaciers are small to-day compared with what they were long ago, in
+Europe and in America. The climate became warmer, and the ice-cap
+retreated. Old moraines show that the ice rivers of the Alps once came
+much farther down the valleys than they do now. Smooth, deeply scored
+domes of rock, the one in Central Park and the bald head of Mount Tom,
+are just like those that lie in Alpine valleys from which the glaciers
+have long ago retreated. There are old moraines far up the sides of
+valleys, showing that once the glaciers were far deeper than now. No
+other power could have brought rocks from strata higher up the
+mountains, and lodged them thus.
+
+Nearer home, Mt. Shasta and Mt. Rainier still have glaciers that have
+dwindled in size, until they bear little comparison to the gigantic
+ice-streams that once filled the smooth beds their puny successors flow
+into. Remnants of glaciers lie in the hollows of the Sierras. We must go
+north to find the snow-fields of Alaska and glaciers worthy to be
+compared with those ancient ice rivers whose work is plainly to be seen,
+though they are gone.
+
+
+
+
+THE GREAT ICE-SHEET
+
+
+Greenland is green only along its southern edge, and only in summer, so
+its name is misleading. It is a frozen continent lying under a great
+ice-cap, which covers 500,000 square miles and is several thousand feet
+in thickness. The top of this icy table-land rises from five thousand to
+ten thousand feet above the sea-level. The long, cold winters are marked
+by great snowfall, and the drifts do not have time to melt during the
+short summer; and so they keep getting deeper and deeper. Streams of ice
+flow down the steeps into the sea, and break off by their weight when
+they are pushed out into the water. These are the icebergs which float
+off into the North Atlantic, and are often seen by passengers on
+transatlantic steamers.
+
+Long ago Greenland better deserved its name. Explorers who have climbed
+the mountain steeps that guard the unknown ice-fields of the interior
+have discovered, a thousand feet above the sea-level, an ancient beach,
+strewn with shells of molluscs like those which now inhabit salt water,
+and skeletons of fishes lie buried in the sand. It is impossible to
+think that the ocean has subsided. The only explanation that accounts
+for the ancient beach, high and dry on the side of Greenland's icy
+mountain is that the continent has been lifted a thousand feet above its
+former level. This is an accepted fact.
+
+We know that climate changes with changed altitude as well as latitude.
+Going up the side of a mountain, even in tropical regions, we may reach
+the snow-line in the middle of summer. Magnolia trees and tree ferns
+once grew luxuriantly in Greenland forests. Their fossil remains have
+been found in the rocks. This was long before the continent was lifted
+into the altitude of ice and snow. And it is believed that the climate
+of northern latitudes has become more severe than formerly from other
+causes. It is possible that the earth's orbit has gradually changed in
+form and position.
+
+If Greenland should ever subside until the ancient beach rests again at
+sea-level, the secrets of that unknown land would be revealed by the
+melting of the glacial sheet that overspreads it. Possibly it would turn
+out to be a mere flock of islands. We can only guess. North America had,
+not so long ago, two-thirds of its area covered with an ice-sheet like
+that of Greenland, and a climate as cold as Greenland's. At this time
+the land was lifted two to three thousand feet higher than its present
+level. All of the rain fell as snow, and the ice accumulated and became
+thicker year by year. Instead of glaciers filling the gorges, a great
+ice flood covered all the land, and pushed southward as far as the Ohio
+River on the east and Yellowstone Park in the west. The Rocky Mountains
+and some parts of the Appalachian system accumulated snow and formed
+local glaciers, separated from the vast ice-sheet.
+
+The unstable crust of the earth began to sink at length, and gradually
+the ice-sheet's progress southward was checked, and it began to recede
+by melting. All along the borders of this great fan-shaped ice-field
+water accumulated from the melting, and flooded the streams which
+drained it to the Atlantic and the Gulf. Icebergs broken off of the edge
+of the retiring ice-sheet floated in a great inland sea. The land sank
+lower and lower until the general level was five hundred to one thousand
+feet lower than it now is. The climate became correspondingly warm, and
+the icebergs melted away. Then the land rose again, and in time the
+inland sea was drained away into the ocean, except for the waters that
+remained in thousands of lakes great and small that now occupy the
+region covered by the ice.
+
+Ancient sea beaches mark the level of high water at the time that the
+flood followed the melting ice. On the shores of Lake Champlain, but
+nearly five hundred feet higher than the present level of the lake,
+curious geologists have found many kinds of marine shells on a
+well-marked old sea beach. The members of one exploring party in the
+same region were surprised and delighted to come by digging upon the
+skeleton of a whale that had drifted ashore in the ancient days when
+the inland sea joined the Atlantic.
+
+Lake Ontario's ancient beach is five hundred feet above the present
+water-level; Lake Erie's is two hundred fifty feet above it; Lake
+Superior's three hundred thirty feet higher than the present beach. No
+doubt when the water stood at the highest level, the Great Lakes formed
+one single sheet of water which settled to a lower level as the rivers
+flowing south cut their channels deep enough to draw off the water
+toward the Gulf. Lake Winnipeg is now the small remnant of a vast lake
+the shores of which have been traced. The Minnesota River finally made
+its way into the Mississippi and drained this great area the stranded
+beaches of which still remain. The name of Agassiz has been given to the
+ancient lake formed by the glacial flood and drained away thousands of
+years ago but not until it had built the terraced beach which locates it
+on the geological map of the region.
+
+When the ice-sheet came down from the north it dragged along all of the
+soil and loose rock material that lay in its path. With the boulders
+frozen into its lower surface it scratched and grooved the firm bedrock
+over which it slid, and rounded it to a smooth and billowy surface. The
+progress of the ice-sheet was southward, but it spread like a fan so
+that its widening border turned to east and west.
+
+When it reached its southernmost limit and began to melt, it laid down a
+great ridge of unsorted rock material, remnants of which remain to this
+day,--the terminal moraine of the ancient ice-sheet. The line of this
+ancient deposit starts on Long Island, crosses New Jersey and
+Pennsylvania, then dips southward, following the general course of the
+Ohio River to its mouth, forming bluffs in southern Ohio, Indiana, and
+Illinois. The line bends upward as it crosses central Missouri, a corner
+of Kansas, and eastern Nebraska, parallel with the course of the
+Missouri.
+
+As the ice-sheet melted, boulders were dropped all over the Northern
+States and Canada. These were both angular and rounded. In some places
+they are scattered thickly over the surface and are so numerous as to be
+a great hindrance to agriculture. In many places great boulders of
+thousands of tons weight are perched on very slight foundations, just
+where they lodged when the ice went off and left them, after carrying
+them hundreds of miles. Around them are scattered quantities of loose
+rock material, not scored or ground as are those which were carried on
+the under-surface of the glacial ice. These unscarred fragments rode on
+the top of the ice. They were a part of the top moraine of the glacial
+sheet.
+
+The finest material deposited is rock meal, ground by the great glacial
+mill, and called "boulder clay." It is a stiff, dense, stony paste in
+which boulders of all sizes, gravel, pebbles, and cobblestones are
+cemented.
+
+The "drift" of the ice-sheet is the rubbish, coarse and fine, it left
+behind as it retreated. Below the Ohio River there is a deep soil
+produced by the decay of rocks that lie under it. North of Ohio is
+spread that peculiar mixture of earth and rock fragments which was
+transported from the north and spread over the land which the ice-sheet
+swept bare and ground smooth and polished.
+
+The drift has been washed away in places by the floods that followed the
+ice. Granite domes are thus exposed, the grooves and scratches of which
+tell in what direction the ice flood was travelling. Miles away from
+that scored granite, but in the same direction as the scratches,
+scattered fragments of the same foundation rock cover fields and
+meadows. Thus, much of the drift material can be traced to its original
+home, and the course of the ice-sheet can be determined. Many immense
+boulders the home of which was in the northern highlands of Canada rode
+southward, frozen into icebergs that floated in the great inland sea.
+Great quantities of d�bris were added to the original glacial drift
+through the agency of these floating ice masses, which melted by slow
+degrees.
+
+
+
+
+FOLLOWING SOME LOST RIVERS
+
+
+What would you think if the boat in which you were floating down a
+pleasant river should suddenly grate upon sand, and you should look over
+the gunwale and find that here the waters sank out of sight, the river
+ended? I believe you would rub your eyes, and feel sure that you were
+dreaming. Do not all rivers flow along their beds, growing larger with
+every mile, and finally empty their waters into a sea, or bay, or lake,
+or flow into some larger stream? This is the way of most rivers, but
+there are exceptions. In the Far West there are some great rivers that
+absolutely disappear before they reach a larger body of water. They
+simply sink away into the sand, and sometimes reappear to finish their
+courses after flowing underground for miles. Do you know the name of one
+great western river of which I am thinking? Is there any stream in your
+neighbourhood which has such peculiar ways?
+
+Down in Kentucky there is a region where, it is said, one may walk fifty
+miles without crossing running water. In the middle of our country, in
+the region of plentiful rainfall, and in a state covered with beautiful
+woodlands and famous for blue grass and other grain crops, it is
+amazing that, over a large area, brooks and larger streams are lacking.
+In most of the state there is plenty of water flowing in streams like
+those in other parts of the eastern half of the United States. In the
+near neighbourhood of this peculiar section of the state the streams
+come to an end suddenly, pouring their water into funnel-shaped
+depressions of the ground called sink-holes. After a heavy rain the
+surface water, accumulating in rivulets, may also be traced to small
+depressions which seem like leaks in the earth's crust, into which the
+water trickles and disappears.
+
+It must have been noticed by the early settlers who came over the
+mountains from the eastern colonies, and settled in the new, wild, hilly
+country, which they called Kentucky. The first settlers built their log
+cabins along the streams they found, and shot deer and wild turkey and
+other game that was plentiful in the woods. The deer showed them where
+salt was to be found in earthy deposits near the streams; for salt is
+necessary to every creature. Deer trails led from many directions to the
+"salt licks" which the wild animals visited frequently.
+
+Perhaps the same pioneers who dug the salt out of the earth found
+likewise deposits of _nitre_, called also _saltpetre_, a very precious
+mineral, for it is one of the elements necessary in the manufacture of
+gunpowder. With the Indians all about him, and often showing themselves
+unfriendly, the pioneer counted gunpowder a necessity of life. He relied
+on his gun to defend and to feed his family. There were men among those
+first settlers who knew how to make gunpowder, and saltpetre was one of
+the things that had to be carried across the mountains into Kentucky,
+until they found it in the hills. No wonder that prospectors went about
+looking for nitre beds in the overhanging ledges of rocks along
+stream-beds. In such situations the deposits of nitre were found. The
+earth was washed in troughs of running water to remove the clayey
+impurity. After a filtering through wood-ashes, the water which held the
+nitre in solution was boiled down, and left to evaporate, after which
+the crystals of saltpetre remained.
+
+Solid masses of saltpetre weighing hundreds of pounds were sometimes
+found in protected corners under shelving rocks. It was no doubt in the
+fascinating hunt for lumps of this pure nitre that the early prospectors
+discovered that the streams which disappeared into the sink-holes made
+their way into caverns underground. Digging in the sides of ravines
+often made the earthy wall cave in, and the surprised prospector stood
+at the door of a cavern. The discoverer of a cave had hopes that by
+entering he might find nitre beds richer than those he could uncover on
+the surface, and this often turned out to be true. The hope of finding
+precious metals and beds of iron ore also encouraged the exploration of
+these caves. By the time the war of 1812 was declared, the mining of
+saltpetre was a good-sized industry in Kentucky. Most of the mineral was
+taken out of small caves, and shipped, when purified, over the
+mountains, on mule-back by trails, and in carts over good roads that
+were built on purpose to bring this mineral product to market. As long
+as war threatened the country, the Government was ready to buy all the
+saltpetre the Kentucky frontiersmen could produce. And the miners were
+constantly in search of richer beds that promised better returns for
+their labour.
+
+It was this search that led to the exploration of the caves discovered,
+although the explorer took his life in his hands when he left the
+daylight behind him and plunged into the under-world.
+
+Not all lost rivers tell as interesting stories or reveal as valuable
+secrets as did those the neighbours of Daniel Boone traced along their
+dark passages underground, and finally saw emerge as hillside springs,
+in many cases, to feed Kentucky rivers. But it is plain that no river
+sinks from sight unless it finds porous or honeycombed rocks that let it
+through. The water seeks the nearest and easiest route to the sea. Its
+weight presses toward the lowest level, always. The more water absorbs
+of acid, the more powerfully does it attack and carry away the substance
+of lime rocks through which it passes.
+
+
+
+
+THE MAMMOTH CAVE OF KENTUCKY
+
+
+There is no more fertile soil in the country than that of the famous
+blue grass region of Kentucky. The surface soil rests upon a deep
+foundation of limestone rocks, and very gradually the plant food locked
+up in these underlying strata is pulled up to the surface by the soil
+water, and greedily appropriated by the roots of the plants.
+
+Part of the water of the abundant rainfall of this region soaks into the
+layers of the lime rock, carrying various acids in solution which give
+it power to dissolve the limestone particles, and thus to make its way
+easily through comparatively porous rock to the very depths of the
+earth. So it has come about that the surface of the earth is undermined.
+Vast empty chambers have been carved by the patient work of trickling
+water, which has carried away the lime that once formed solid and
+continuous layers of the earth's crust. We must believe that the work
+has taken thousands of years, at least, for no perceptible change has
+come to these wonderful caves since the discovery and exploration of
+them a century and more ago.
+
+The streams that flow into the region of these caves disappear suddenly
+into sink-holes and flow through caverns. After wearing away their
+subterranean channels, leaping down from one level to another, forming
+waterfalls and lakes, some emerge finally through hillsides in the form
+of springs.
+
+The cavern region of Kentucky covers eight thousand square miles. The
+underground chambers found there are in the limestone rock which varies
+from ten to four hundred feet in thickness, and averages a little less
+than two hundred feet. Over this territory the number of sink-holes
+average one hundred to the square mile; and the streams that have poured
+their water into these basins have made a network of open caverns one
+hundred thousand miles in length.
+
+A great many small caverns have been thoroughly explored and are famous
+for their beauty. The Diamond Cave is one of the most splendid, for it
+is lined with walls and pillars of alabaster that sparkle in the
+torchlight with crystals that look like veritable diamonds. Beautiful
+springs and waterfalls are found in many caves, but the grandest of all
+is the Mammoth Cave, beside which no other is counted worthy to be
+compared.
+
+Great tales the miners told of the wonder and the beauty of these
+caverns, the walls of which were supported by arching alabaster columns
+and wonderful domes, of indescribable beauty of form and colouring. In
+1799, the year that Washington died, a pioneer discovered the entrance
+to a cave, the size and beauty of which surpassed anything he had seen
+before. After exploring it for a short distance he returned home and
+took his whole family with him to enjoy the first view of the wonderful
+cavern he had discovered. They carried pine knots and a lighted torch,
+by which they made their way for some distance, but the torch was
+accidentally extinguished and they groped their way in darkness and
+missed the entrance. Without anything to guide them, they wandered in
+darkness for three days, and were almost dead when at last they stumbled
+upon the exit. This is the doorway of the Mammoth Cave of Kentucky, one
+of the wonders of the world.
+
+This was a terrible experience. The next persons who attempted to
+explore the new cave were better provisioned against the chance of
+spending some time underground. The pioneers found rich deposits of
+nitre in the "Great Cave," as they called it. Scientists visited it and
+explored many of its chambers. The reputation of this cavern has been
+spread by thousands of visitors who have come from all over the world to
+see it. The cave has not yet been completely explored. The regular
+tours, on which the guides conduct visitors, cover but a small part of
+the one hundred and fifty miles measured by the two hundred or more
+avenues. The passages wind in and out, crossing each other, sometimes at
+different levels, and forming a network of avenues in which the
+unaccustomed traveller would surely be lost. The old guides know every
+inch of their regular course, and their quaint and edifying talk adds
+greatly to the pleasure of the visitors.
+
+From the hotel, parties are organized for ten o'clock in the morning and
+seven o'clock in the evening. Each visitor is provided with a lard-oil
+lamp. The guide carries a flask of oil and plenty of matches. No special
+garb is necessary, though people usually dress for comfort, and wear
+easy shoes. The temperature of the cave is uniform winter and summer,
+varying between fifty-three and fifty-four degrees Fahrenheit.
+
+The cave entrance is an arch of seventy-foot span in the hillside. A
+winding flight of seventy stone steps leads the party around a
+waterfall, into a great chamber under the rocks. Then the way goes
+through a narrow passage, where the guide unlocks an iron gate to let
+them in. The visitors now leave all thoughts of daylight behind, for the
+breeze that put out their lights as they entered the cave is past, and
+they stand in the Rotunda, a vast high-ceilinged chamber, silent and
+impressive, with walls of creamy limestone, encrusted with gypsum, which
+has been stained black by manganese. From the vestibule on, each passage
+and each room has a name, based upon some historic event or some fancied
+resemblance. The Giant's Coffin is a great kite-shaped rock lying in one
+of the rooms of the cave. The Star Chamber has a wonderful
+crystal-studded dome in which the guide produces the effect of a sunrise
+by burning coloured lights. Bonfires built at suitable points produce
+wonderful shadow effects, which are like nothing else in the world. The
+old saltpetre vats which the visitors pass in taking the "Long Route"
+through the cave, point them back to the days during the War of 1812,
+when this valuable mineral was extracted from the earth in the floor of
+the cave. The industry greatly enriched the thrifty owners of the cave,
+but the works were abandoned after peace was declared.
+
+It must be a wonderful experience to walk steadily for nine hours over
+the Long Route, for so pure is the air and so wonderful is the scenery
+that people rarely complain of fatigue when the experience is over.
+There is no dust on the floors of these subterranean chambers, and they
+are not damp except near places where water trickles, here and there, in
+rivulets and cascades. Pools of water at the bottoms of pits so deep
+that a lighted torch requires several seconds to reach the bottom, and
+rivers and lakes of considerable size, show where some of the surface
+water goes to. A strange underground suction creates whirlpools in some
+of these streams. People go in boats holding twenty passengers for a row
+on Echo River, and the guide dips up with a net the blind fish and
+crayfish and cave lizards which inhabit these subterranean waters. The
+echoes in various chambers of the Mammoth Cave are remarkable. In some
+of them a song by a single voice comes back with full chords, as if
+several voices carried the different parts. The single notes of flute
+and cornet are returned with the same beautiful harmonies. A pistol shot
+is given back a dozen times, the sound rebounding like a ball from rock
+to rock of the arching walls. The vibrations of the water made by the
+rower's paddles re�cho in sounds like bell notes, and they are
+multiplied into harmonies that suggest the chimes in the belfry of a
+cathedral.
+
+The walls of various chambers differ from each other according to the
+minerals that compose them. Some are creamy white limestone arches, some
+are walled with black gypsum, some are hung with great curtains of
+stalagmites, solid but suggesting the lightness and grace of folds of
+cr�pe. Under such hangings the floor is built up in stalactites. The
+mineral-laden water, the constant drip of which has produced a hanging,
+icicle-like stalagmite, has built up the stalactite to meet it.
+
+Probably nothing is more beautiful than the flower-like crystals that
+bloom all over the walls of a chamber called "Mary's Bower." The floor,
+even, sparkles with jewels that have fallen from the wonderful and
+delicate flower clusters built from deposits of the lime-laden water
+which goes on building and replacing the bits that fall. "Martha's
+Vineyard" is decorated with nodules, like bunches of grapes, that
+glisten as if the dew were on them. The white gypsum in some caves makes
+the walls look as if they were carved out of snow. Still others have
+clear, transparent crystals that make them gleam in the torches' light
+as if the walls were encrusted with diamonds.
+
+The cave region of Indiana is also famous. The great Wyandotte Cave in
+Crawford County is the most noted of many similar caverns. In some of
+the chambers, bats are found clinging to the ceiling, heads downward,
+like swarms of bees. The caverns of Luray, in Virginia, are complex and
+wonderful in their structure, and famous for the beautiful stalactites
+and stalagmites they contain. But there is no cave in this country so
+wonderful and so grand in its dimensions as the Mammoth Cave in
+Kentucky.
+
+
+
+
+LAND-BUILDING BY RIVERS
+
+
+Once a year, when the rainy season comes in the mountainous country
+south of Egypt, the old Nile floods its banks and spreads its slimy
+waters over the land, covering the low plains to the very edge of the
+Sahara Desert. The people know it is coming, and are prepared for this
+flood. We should think such an overflow of our nearest river a monstrous
+calamity, but the Egyptians bless the river which blesses them. They
+know that without the Nile's overflow their country would be added to
+the Desert of Sahara. In a short time after the overflow, the river
+reaches its highest point and begins to ebb. Canals lying parallel to
+its course are filled with water which is saved for use in the hot, dry
+summer. As the flood goes down, a deposit of slimy mud lies as a rich
+fertilizer on the land. It is this and the water which the earth has
+absorbed that make Egypt one of the most fertile agricultural countries
+in the world.
+
+The region covered by the Nile's overflow is the flood plain of this
+river. On this plain the Pyramids, the Sphinx, and other famous
+monuments of Egypt stand. The statue of Rameses II. built 3,000 years
+ago, has its base buried nine feet deep in the rich soil made of Nile
+sediment. A well dug in this region goes through forty feet of this soil
+before striking the underlying sand. How many years ago did the first
+Nile overflow take place? We may begin our calculation by finding out
+the average yearly deposit. It is a slow process that accumulates but
+nine feet in 3,000 years. If you were in Egypt when the Nile went back
+into its banks, you would see that the scum it leaves in a single
+overflow adds not a great deal to the thickness of the soil. Possibly
+floods have varied in their deposits from year to year, so that any
+calculation of the time it took to build that forty feet of surface soil
+must be but a rough estimate. This much we know: it has been an
+uninterrupted process which has taken place within the present
+geological epoch, "the Age of Man."
+
+Not all the rich sediment the Nile brings down is left on the level
+flood plain along its course. A vast quantity is dumped at the river's
+mouth, where the tides of the Mediterranean check the river's current.
+Thus the great delta is formed. The broad river splits into many mouths
+that spread out like a fan and build higher and broader each year the
+mud-banks between the streams. Upper Egypt consists of river swamps.
+Lower Egypt, from Cairo to the sea, is the delta built by the river
+itself on sea bottom. From the head of the delta, where the river
+commences to divide, to the sea, is an area of 10,000 square miles made
+out of material contributed by upper Egypt, and built by the river.
+Layer upon layer, it is constantly forming, but most rapidly during the
+season of floods.
+
+Coming closer home, let us look at the map of the Mississippi Valley.
+Begin as far north as St. Louis. For the rest of its course the
+Mississippi River flows through a widening plain of swamp land, flooded
+in rainy seasons. Through this swampy flood plain the river meanders;
+its current, heavily loaded with sediment, swings from one side to the
+other of the channel, building up here, wearing away there, and
+straightening its course when the curves become so sharp that their
+sides meet. Then the current breaks through the thin wall, and a bayou
+of still water is left behind.
+
+Below Baton Rouge the Mississippi breaks into many mouths, that spread
+and carry the water of the great river into the Gulf of Mexico. The Nile
+delta is triangular, like delta, [Greek: D], the fourth letter of the
+Greek alphabet; but the Mississippi's delta is very irregular. The main
+mouth of the river flows fifty miles out into the Gulf between
+mud-banks, narrow and low. At the tip it branches into several streams.
+
+From the mouth of the Ohio to the Gulf, the Mississippi flood plain
+covers 30,000 square miles. Over this area, sediment to an average depth
+of fifty feet has been laid down. In earlier times the river flooded
+this whole area, when freshets swelled its tributaries in the spring.
+The flood plain then became a sea, in the middle of which the river's
+current flowed swiftly. The slow-flowing water on each side of the main
+current let go of its burden of sediment and formed a double ridge.
+Between these two natural walls the main river flowed. When its level
+fell, two side streams, running parallel with the main river drained the
+flood plains on each side into the main tributaries to right and left.
+These natural walls deposited when the river was in flood are called
+_levees_. Each heavy flood builds them higher, and the bed of the stream
+rises by deposits of sediment. So it happens that the level of the river
+bed is higher than the level of its flood plain.
+
+This is an interesting fact in geology. But the people who have taken
+possession of the rich flood plain of the Mississippi River, who have
+built their homes there, drained and cultivated the land, and built
+cities and towns on the areas reclaimed from swamps, recognize the
+elevation of the river bed as the greatest danger that threatens them.
+Suppose a flood should come. Even if it does not overflow the levees, it
+may break through the natural banks and thus overflow the cities and the
+farm lands to left and right.
+
+Instead of living in constant fear of such a calamity, the people of the
+Mississippi flood plain have sought safety by making artificial levees,
+to make floods impossible. These are built upon the natural levees. As
+the river bed rises by the deposit of mud, the levees are built higher
+to contain the rising waters. No longer does the rich soil of the
+Mississippi flood plain receive layers of sediment from the river's
+overflow. The river very rarely breaks through a levee. The United
+States Government has spent great sums in walling in the river, and each
+state along its banks does its share toward paying for this
+self-protection.
+
+By means of _jetties_ the river's current is directed into a
+straightened course, and its power is expended upon the work of
+deepening its own channel and carrying its sediment to the Gulf. Much as
+the river has been forced to do in cleaning its own main channel,
+dredging is needed at various harbours to keep the river deep enough for
+navigation. The forests of the mountain slopes in Colorado are being
+slaughtered, and the headwaters of the Missouri are carrying more and
+more rocky d�bris to choke the current of the Mississippi. Colorado soil
+is stolen to build land in the vast delta, which is pushing out into the
+Gulf at the rate of six miles in a century--a mile in every sixteen
+years. The Mississippi delta measures 14,000 square miles. With the
+continued denuding of mountain slopes, we shall expect the rate of delta
+growth to be greatly increased, until reforesting checks the destructive
+work of wind and water.
+
+
+
+
+THE MAKING OF MOUNTAINS
+
+
+The gradual thickening and shrinking of the earth's crust as it cools
+have made the wrinkles we call mountain systems. Through millions of
+years the globe has been giving off heat to the cold sky spaces through
+which it swings in its orbit around the sun. The cooling caused the
+contraction of the outer layer to fit the shrinking of the mass. When a
+plump peach dries on its pit, the skin wrinkles down to fit the dried
+flesh. The fruit shrinks by loss of water, just as the face of an old
+person shrinks by loss of fat. The skin becomes wrinkled in both cases.
+
+The weakest places in the earth's crust were the places to crumple,
+because they could not resist the lateral pressure that was exerted by
+the shrinking process. Along the shores of the ancient seas the rivers
+piled great burdens of sediment. This caused the thin crust to sink and
+to become a basin alongside of a ridge. The wearing away of the land in
+certain places lightened and weakened the crust at these places, so that
+it bent upward in a ridge.
+
+Perhaps the first wrinkles were not very high and deep. The gradual
+cooling must have exerted continued pressure, and the wrinkles have
+become larger. It is not likely that new wrinkles would be formed as
+long as the old ones would crumple and draw up into narrower, steeper
+slopes, in response to the lateral crushing.
+
+We can imagine those first mountains rising as folds under the sea.
+Gradually their bases were narrowed, and their crests lifted out of the
+water. They rose as long, narrow islands, and grew in size as time went
+on.
+
+Why is the trend of the great mountain systems almost always north and
+south? Study the map of the continents and see how few cross ranges are
+shown, and how short they are, compared with the others. The molten
+globe bulged at its equator, as it rotated on its axis. The moon added
+its strong pulling force to make it bulge still more. As the crust
+thickened, it became less responsive to the two forces that caused it to
+bulge. The shrinkage was greatest where the globe had been most pulled
+out of shape. The rate of the earth's rotation is believed to have
+diminished. Every change tended to let the earth draw in its (imaginary)
+belt, a notch at a time. The forces of contraction acted along the line
+of the equator, and formed folds running toward the poles. In this early
+time the great mountain systems were born, and they grew in size
+gradually, from small beginnings.
+
+These mountains of upheaval, made by the bending of the earth's crust,
+and the formation of alternating ridges and depressed valleys, are many.
+The earth is old and much wrinkled. Other mountains have been formed by
+forces quite different. Volcanic mountains have been far more numerous
+in ages gone than they are now.
+
+Mt. Hood and Mt. Rainier are peaks built up by the materials thrown out
+of the craters of volcanoes dead these thousands of years. Vesuvius is
+at present showing us how volcanic mountains are made. Each eruption
+builds larger the cone--that is, the chimney through which the molten
+rocks, the ashes, and the steam are ejected. Side craters may open, the
+main cone be broken and its form changed, but the mass of lava and
+stones and ashes grows with each eruption. The mountain grows by the
+additions it receives. �tna is a mountain built of lava.
+
+A third mountain system grew, not by addition, but by subtraction. The
+Catskills illustrate this type. This group of mountains is the remnant
+of a table-land made of level layers of red sandstone. The rest of the
+high plain has been cut down and carried away, leaving these picturesque
+hills, the survival of which is as much a mystery as the disappearance
+of the balance of the plateau of which they were once a part.
+
+The fold that forms a typical mountain ridge has a cone of granite, the
+original rock foundation of the earth, and on this are layers of
+stratified rock, ancient deposits of sediment carried to the sea by
+streams. When exposed to wind and rain, the ridge is gradually worn
+down. In some places the water cuts away the soft rock and forms a
+stream-bed, that cuts deeper and deeper, using the rock fragments as its
+tools. Often the layers of aqueous rocks are cut through, and the
+granite exposed.
+
+Sometimes the hardest stratified rock-beds resist the water and the wind
+and are left as a series of ridges along the sides of the main range.
+The crumpling forces may crack the ridge open for its whole length, and
+one side of the chasm may slip down and the other go up. The result is a
+sheer wall of exposed rock strata, layers of which correspond with those
+that lie far below the top of the portion that slid down in the great
+upheaval and subsidence that parted them. These slips are known as
+_faults_.
+
+
+
+
+THE LAVA FLOOD OF THE NORTHWEST
+
+
+We know little about the substance that occupies the four thousand miles
+of distance between the surface and the centre of our earth. We know
+that the terrible weight borne by the central mass compresses it, so
+that the interior must grow denser as the core is approached. Scientists
+have weighed the earth, and tell us that the crust is lighter than the
+rest. The supposition is that there is a great deal of iron in the
+interior, and possibly precious metals, too.
+
+Our deepest wells and mines go down about a mile, then digging stops, on
+account of the excessive heat. But the crumpling of the crust, and the
+wearing away of the folded strata by wind and running water, have laid
+bare rocks several miles in thickness on the slopes of mountains, and
+exposed the underlying granite, on which the first sedimentary rocks
+were deposited. On this granite lie stratified rocks, which are
+crystalline in texture. These are the beds, sometimes miles in depth,
+called _metamorphic_ rocks, formed by water, then transformed by heat.
+
+The wearing away of rocks by wind and water has furnished the materials
+out of which the aqueous rocks have been made. Layers upon layers of
+sandstone, shales, limestone, and the like, are exposed when a river
+cuts a canyon through a plateau. The layered deposits of d�bris at the
+mouth of the river make new aqueous rocks out of old. Every sandy beach
+is sandstone in the making. This work is never ended.
+
+In the early days the earth's crust often gaped open in a mighty crater
+and let a flood of lava overspread the surface. The ocean floor often
+received this flood of melted rock. In many places the same chimney
+opened again and again, each time spreading a new layer of lava on top
+of the old, so that the surface has several lava sheets overlying the
+aqueous strata.
+
+If the hardened lava sheet proved a barrier to the rising tide of molten
+lava in the chimney it was often forced out in sheets between the layers
+of aqueous rocks. Wherever the heated material came into contact with
+aqueous rocks it transformed them, for a foot or more, into crystalline,
+metamorphic rocks.
+
+A chimney of lava is called a _dike_. In mountainous countries dikes are
+common. Sometimes small, they may also be hundreds of feet across, often
+standing high above the softer strata, which rains have worn away. Dikes
+often look like ruined walls, and may be traced for miles where they
+have been overturned in the mountain-making process.
+
+The great lava flood of the Northwest happened when the Coast Range was
+born. Along the border of the Pacific Ocean vast sedimentary deposits
+had accumulated during the Cretaceous and Tertiary Periods. Then the
+mighty upheaval came, the mountain ridge rose at the end of the Miocene
+epoch and stretched itself for hundreds of miles through the region
+which is now the coast of California and Oregon. Great fissures opened
+in the folded crust, and floods of lava overspread an area of 150,000
+square miles. A dozen dead craters show to-day where those immense
+volcanic chimneys were. The depth of the lava-beds is well shown where
+the Columbia River has worn its channel through. Walls of lava three
+thousand feet in thickness rise on each side of the river. They are made
+of columns of basalt, fitted together, like cells of a honeycomb, and
+jointed, forming stone blocks laid one upon another. The lava shrinks on
+cooling and forms prisms. In Ireland, the Giants' Causeway is a famous
+example of basaltic formation. In Oregon, the walls of the Des Chutes
+River show thirty lava layers, each made of vertical basalt columns. The
+palisades of the Hudson, Mt. Tom, and Mt. Holyoke are examples on the
+eastern side of the continent of basaltic rocks made by lava floods.
+
+Northern California, northwestern Nevada, and large part of Idaho,
+Montana, Oregon, and Washington are included in the basin filled with
+lava at the time of the great overflow, which extended far into British
+Columbia. It is probable that certain chimneys continued to discharge
+until comparatively recent times. Mt. Rainier, Mt. Shasta, and Mt. Hood
+are among dead volcanoes.
+
+Quite a different history has the great Deccan lava-field of India,
+which covers a larger area than the basin of our Northwest, and is in
+places more than a mile in depth. It has no volcanoes, nor signs of any
+ever having existed. The floods alone overspread the region, which shows
+no puny "follow-up system" of scattered craters, intermittently in
+eruption.
+
+
+
+
+THE FIRST LIVING THINGS
+
+
+Strange days and nights those must have been on the earth when the great
+sea was still too hot for living things to exist in it. The land above
+the water-line was bare rocks. These were rapidly being crumbled by the
+action of the air, which was not the mild, pleasant air we know, but was
+full of destructive gases, breathed out through cracks in the thin crust
+of the earth from the heated mass below. If you stand on the edge of a
+lava lake, like one of those on the islands of the Hawaiian group, the
+stifling fumes that rise might make you feel as if you were back at the
+beginning of the earth's history, when the solid crust was just a thin
+film on an unstable sea of molten rock, and this volcano but one of the
+vast number of openings by which the boiling lava and the condensed
+gases found their way to the surface. Then the rivers ran black with the
+waste of the rocky earth they furrowed, and there was no vegetation to
+soften the bleakness of the landscape.
+
+The beginnings of life on the earth are a mystery. Nobody can guess the
+riddle. The earliest rocks were subjected to great heat. It is not
+possible that life could have existed in the heated ocean or on the
+land. Gradually the shores of the seas became filled up with sediment
+washed down by the rivers. Layer on layer of this sediment accumulated,
+and it was crumpled by pressure, and changed by heat, so that if any
+plants or animals had lived along those old shores their remains would
+have been utterly destroyed.
+
+Rocks that lie in layers on top of these oldest, fire-scarred
+foundations of the earth show the first faint traces of living things.
+Limestone and beds of iron ore are signs of the presence of life. The
+first animals and plants lived in the ancient seas.
+
+From the traces that are left, we judge that the earliest life forms
+were of the simplest kind, like some plants and animals that swim in a
+drop of water. Have you ever seen a drop of pond water under a compound
+microscope? It is a wonder world you look into, and you forget all the
+world besides. You are one of the wonderful higher animals, the highest
+on the earth. You focus on a shapeless creature that moves about and
+feels and breathes, but hasn't any eyes or mouth or stomach--in fact, it
+is the lowest form of animal life, and one of the smallest. It is but
+one of many animal forms, all simple in structure, but able to feed and
+grow and reproduce their kind.
+
+Gaze out of the window on the garden, now. The flowering plants, the
+green grass, and the trees are among the highest forms of plants. In the
+drop of water under the microscope tiny specks of green are floating.
+They belong to the lowest order of plants. Among the plant and the
+animal forms that have been studied and named, are a few living things
+the places of which in the scale are not agreed upon. Some say they are
+animals; some believe they are plants. They are like both in some
+respects. It is probable that the first living things were like these
+confusing, minute things--not distinctly plants or animals, but the
+parent forms from which, later on, both plants and animals sprang.
+
+The lowest forms of life, plant and animal, live in water to-day. They
+are tiny and their bodies are made of a soft substance like the white of
+an egg. If these are at all like the living creatures that swarmed in
+the early seas, no wonder they left no traces in the rocks of the early
+part of the age when life is first recorded by fossils. Soft-bodied
+creatures never do.
+
+Some of the animals and the plants in the drop of water under the
+microscope have body walls of definite shapes, made of lime, or of a
+glassy substance called silica. When they die, these "skeletons" lie at
+the bottom of the water, and do not decay, as the living part of the
+body does, because they are mineral. Gradually a number of these shells,
+or hard skeletons, accumulate. In a glass of pond water they are found
+at the bottom, amongst the sediment. In a pond how many thousands of
+these creatures must live and their shells fall to the bottom at last,
+buried in the mud!
+
+So it is easy to understand why the first creatures on earth left no
+trace. The first real fossils found in the rocks are the hard shells or
+skeletons of the first plants and animals that had hard parts.
+
+
+
+
+AN ANCIENT BEACH AT EBB TIDE
+
+
+When the tide is out, the rocks on the Maine coast have plenty of living
+creatures to prove this northern shore inhabited. Starfishes lurk in the
+hollows, and the tent-shaped shells of the little periwinkle encrust the
+wet rocks. Mussels cling to the rocks in clumps, fastened to each other
+by their ropes of coarse black hair. The furry coating of sea mosses
+that encrust the rocks is a hiding-place for many kinds of living
+things, some soft-bodied, some protected by shells. The shallow water is
+the home of plants and animals of many different kinds. As proof of this
+one finds dead shells and fragments of seaweeds strewn on the shore
+after a storm.
+
+Along the outer shores of the Cape Cod peninsula and down the Jersey
+coast, the sober colouring of the shells of the north gives way to a
+brighter colour scheme. In the warmer waters, life becomes gayer, if we
+may judge by the rich tints that ornament the shells. The kinds of
+living creatures change. They are larger and more abundant. The seaweeds
+are more varied and more luxuriant in growth.
+
+When we reach the shores of the West Indian islands and the keys of
+Florida the greatest abundance and variety of living forms are found.
+The submerged rocks blossom with flower-like sea anemones of every
+colour. Corals, branching like trees and bushes on the sea floor, form
+groves under water. Among them brilliant-hued fishes swim, and highly
+ornamented shells glide, as people know who have gazed through the glass
+bottoms of the boats built especially to show visitors the wonderful sea
+gardens at Nassau, Bahama Islands, and at Santa Catalina Island,
+southern California.
+
+On every beach the skeletons of animals which die help to build up the
+land; though the process is not so rapid in the north as on the shores
+that approach the tropics. The coast of Florida has a rim of island
+reefs around it built out of coral limestone. Indeed, the peninsula was
+built by coral polyps. Houses in St. Augustine are built of coquina
+rock, which is simply a mass of broken shells held together by a lime
+cement. Every sea beach is packed with shells and other remnants of
+animals and plants that live in the shallow waters. Deeper and deeper
+year by year the sand buries these skeletons, and many of them are
+preserved for all time.
+
+Thus what is sandy beach to-day may, a few million years from now, be
+uncovered as a ledge of sandstone with the prints of waves distinctly
+shown, and fossil shells of molluscs, skeletons of fishes, and branches
+of seaweed--all of them different from those then growing upon the
+earth.
+
+In the neighbourhood of Cincinnati there have been uncovered banks of
+stone accumulated along the border of an ancient sea. From the sides of
+granite highlands streams brought down the sand built into these oldest
+sandstone rocks. The fine mud which now appears as beds of slate was the
+decay of feldspar and hornblende in the same granite. Limestone beds are
+full of the fossil shells of creatures that lived in the shallow seas.
+Their skeletons, accumulating on the bottom, formed deep layers of
+limestone mud. These rocks preserve, by the fossils they contain, a
+great variety of shellfish which had limy skeletons. The sea fairly
+swarmed along its shallow margin with these creatures. We might not
+recognize many of the shells and other curious fossils we find in the
+rock uncovered by the workmen who are cutting a railroad embankment.
+They are not exactly like the living forms that grow along our beaches
+to-day, but they are enough like them for us to know that they lived
+along the seashore, and if we had time to examine all the rocks of this
+kind preserved in a museum we should decide that seashore life was quite
+as abundant then as it is now. The pressed specimens of plants of those
+earliest seashores are mere imprints showing that they were pulpy and
+therefore gradually decayed. Only their shape is recorded by dark stains
+made by each branching part. The decay of the vegetable tissue painted
+the outline on the rock which when split apart shows us what those
+ancient seaweeds looked like. They belonged to the group of plants we
+call kelp, or tangle, which are still common enough in the sea, though
+the forms we now have are not exactly like the old ones. Seaweeds belong
+to the very lowest forms of plants.
+
+[Illustration: Crinoid from Indiana]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Ammonite from Jurassic of England]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Fossil corals Coquina, Hippurite limestone]
+
+The limestones are full of fossils of corals. Indeed, there must have
+been reefs like those that skirt Florida to-day built by these
+lime-building polyps. Their forms are so well preserved in the rocks
+that it is possible to know just how they looked when they grew in the
+shallows.
+
+One very common kind is called a cup coral, because the polyp formed a
+skeleton shaped like a cup. The body wall surrounded the skeleton, and
+the arms or tentacles rose from the centre of the funnel-like depression
+in the top. Little cups budded off from their parents, but remained
+attached, and at length the skeletons of all formed great masses of limy
+rock. Some cup corals grew in a solid mass, the new generation forming
+an outer layer, thus burying the parent cups.
+
+A second type of corals in these oldest limestones is the honeycomb
+group. The colonies of polyps lived in tubes which lengthened gradually,
+forming compact, limy cylinders like organ pipes, fitted close together.
+The living generation always inhabited the upper chambers of the tubes.
+A third type is the chain coral, made of tubes joined in rows, single
+file like pickets of a fence. But these walls bend into curious
+patterns, so that the cross-section of a mass of them looks like a
+complex pattern of crochet-work, the irregular spaces fenced with chain
+stitches. Each open link is a pit in which a polyp lived.
+
+Among the corals are sprays of a fine feathery growth embedded in the
+limestone. Fine, straight, splinter-like branches are saw-toothed on one
+or both edges. These limy fossils might not be seen at all, were they
+not bedded in shales, which are very fine-grained. Here again are the
+skeletons of animals. Each notch on each thread-like branch was the home
+of a tiny animal, not unlike a sea anemone and a coral polyp.
+
+To believe this story it is necessary only to pick up a bit of dead
+shell or floating driftwood on which a feathery growth is found. These
+plumes, like "sea mosses," as they are called, are not plants at all,
+but colonies of polyps. Each one lived in a tiny pit, and these pits
+range one above the other, so as to look like notches on the thread-like
+divisions of the stem. Put a piece of this so-called "sea moss" in a
+glass of sea water, and in a few moments of quiet you will see, by the
+use of a magnifying glass, the spreading arms of the polyp thrust out of
+each pit.
+
+The ancient seas swarmed with these living hydrozoans, and their remains
+are found preserved as fossils in the shales which once were beds of
+soft mud.
+
+The hard shells of sea urchins and starfishes are made of lime. In the
+ancient seas, starfishes were rare and sea urchins did not exist, but
+all over the sea bottom grew creatures called crinoids, the soft parts
+of which were enclosed in limy protective cases and attached to rocks on
+the sea bottom by means of jointed stems. No fossils are more plentiful
+in the early limestones than these wonderful "stone lilies." Indeed, the
+crinoidal limestone seemed to be built of the skeletons of these
+animals. The lily-like body was flung open, as a lily opens its calyx,
+when the creature was feeding. But any alarm caused the tentacles to be
+drawn in, and the petal-like divisions of the body wall to close tightly
+together, till that wall looked like an unopened bud.
+
+On the bottom of the Atlantic, near the Bahama Islands, these stone
+lilies are still found growing. Their jointed stems and body parts are
+as graceful in form and motion as any lily. The creature's mouth is in
+the centre of the flower-like top, and it feeds like the sea urchin, on
+particles obtained in the sea water.
+
+The old limestones contain great quantities of "lamp shells," which are
+old-fashioned bivalves. Their shells remind us of our bivalve clams and
+scallops, but the internal parts were very different. The gills of clams
+and oysters are soft parts. Inside of the lamp shells are coiled, bony
+arms, supporting the fringed gills.
+
+It is fortunate for us that a few lamp shells still live in the seas. By
+studying the soft parts of these living remnants of a very old race we
+can know the secrets of the lives of those ancient lamp shells, the
+soft parts of which were all washed away, and the fossil shells of which
+are preserved. Gradually the lamp shells died out, and the modern
+bivalves have come to take their places. Just so, the ancient crinoids
+are now almost extinct; the sea urchins and the starfishes have
+succeeded them.
+
+The chambered nautilus has its shell divided by partitions and it lives
+in the outer chamber, a many-tentacled creature, that is a close
+relative of the soft-bodied squid. In the ancient seas the same family
+was represented by huge creatures the shells of which were chambered,
+but not coiled. Their abundance and great size are proved by the rocks
+in which their fossils are preserved. Some of them must have been the
+rulers of the sea, as sharks and whales are to-day. Fossil specimens
+have been found more than fifteen feet long and ten inches in diameter
+in the ancient rocks of some of the Western States. It is possible to
+read from the lowest rock formations upward, the rise of these sea
+giants and their gradual decline. Certain strata of limestone contain
+the last relics of this race, after which they became extinct. As the
+straight-chambered forms diminished, great coiled forms became more
+abundant, but all died out.
+
+One of the most abundant fossil animals in ancient rocks is called a
+trilobite. Its body is divided by two grooves into three parts, a
+central ridge extending the whole length of the body and two side
+ridges. The front portion of the shell formed the head shield, and
+behind the main body part was a little tail shield. The skeleton was
+formed of many movable jointed plates, and the creature had eyes set in
+the head shield just as the king crab's are set. Jointed legs in pairs
+fringed each side of the body. Each leg had two branches, one for
+walking, the other for swimming. A pair of feelers rose from the head.
+The body could be rolled into a ball when danger threatened, by bringing
+head and tail together.
+
+These remarkable, extinct trilobites were the first crustaceans. Their
+nearest living relative to-day is the horseshoe crab. The fresh-water
+crayfish and the lobster are more distant relatives: so are the shrimps
+and the prawns. No such abundance of these creatures exists to-day as
+existed when the trilobites thronged the shallows. So well preserved are
+these skeletons that, although there are no living trilobites for
+comparison, it is possible to find out from the fossil enough about
+their structure to know how they fed and lived their lives along with
+the straight-horns which were the scavengers of those early seas and the
+terror of smaller creatures. The trilobites throve, and, dying, left
+their record in the rocks; then disappeared entirely. We find their
+fossils in a great variety of forms, shapes, and sizes. The smallest is
+but a fraction of an inch long, the largest twenty inches long.
+
+The ancient rocks, in which these lower forms of life have left their
+fossils, are known as the Silurian system. The time in which these rocks
+were accumulating under the seas covers a vast period. We call it the
+Age of Invertebrates, because these soft-bodied, hard-shelled animals,
+the crinoids, the molluscs, and the trilobites, with bony external
+skeletons and no backbones, were the most abundant. They overshadowed
+all other forms of life. The rocks of this wonderful series were formed
+on the shores of a great inland sea that covered the central portion of
+North America. In the ages that followed, these rocks were covered
+deeply with later sediments. But the upheavals of the crust have broken
+open and erosion has uncovered these strata in different regions.
+Geologists have found written there, page upon page, the record of life
+as it existed in the early seas.
+
+
+
+
+THE LIME ROCKS
+
+
+"Hard" water and "soft" water are very different. The rain that falls
+and fills our cisterns is not softer or more delightful to use than the
+well water in some favoured regions. In it, soap makes beautiful, creamy
+suds, and it is a real pleasure to put one's hands into it. But in hard
+water soap seems to curdle, and some softening agent like borax has to
+be added or the water will chap the hands. There is little satisfaction
+in using water of this kind for any purpose.
+
+Hard water was as soft as any when it fell from the sky; but the rain
+water trickled into the ground and passed through rocks containing lime.
+Some of this mineral was absorbed, for lime is readily soluble in water.
+Clear though it may be, water that has lime in it has quite a different
+feeling from rain water. Blow the breath into a basin of hard water, and
+a milky appearance will be noted. The carbonic acid gas exhaled from the
+lungs unites with the invisible lime, causing it to become visible
+particles of carbonate of lime, which fall to the bottom of the basin.
+
+Nearly all well water is hard. So is the water of lakes and rivers and
+the ocean, for limestone is one of the most widely distributed rocks in
+the surface of the earth. Rain water makes its way into the earth's
+crust, absorbs mineral substances, and collects in springs which feed
+brooks and rivers and lakes. Wells are holes in the ground which bore
+into water-soaked strata of sand.
+
+We gain something from the lime dissolved in hard water, for it is an
+essential part of our food. We must drink a certain amount of water each
+day to keep the body in perfect health. The lime in this water goes
+chiefly to the building of our bones. Plant roots take up lime in the
+water that mounts as sap through the plant bodies. We get some of the
+lime we need in vegetable foods we eat.
+
+All of the kingdom of vertebrate animals, from the lowest forms to the
+highest, all of the shell-bearing animals of sea and land, require lime.
+Many of the lower creatures especially these in the sea, such as corals
+and their near relatives, encase themselves in body walls of lime. They
+absorb the lime from the sea water, and deposit it as unconsciously as
+we build the bony framework of our bodies.
+
+All the bone and shell-bearing creatures that die on the earth and in
+the sea restore to the land and to the water the lime taken by the
+creatures while they lived. Carbonic acid gas in the water greatly
+hastens the dissolving of dead shells. Carbonic acid gas, whether free
+in the air, or absorbed by percolating water, hastens the dissolving of
+skeletons of creatures that die upon land. Then the raw materials are
+built again into lime rocks underground.
+
+The lime rocks are the most important group in the list of rocks that
+form the crust of the earth. They are made of the elements calcium,
+carbon, and oxygen, yet the different members of this calcite group
+differ widely in composition and appearance. So do oyster shells and
+beef bones, though both contain quantities of carbonate of lime.
+
+Calcite is a soft mineral, light in weight, sometimes white, but oftener
+of some other colour. It may be found crystallized or not. Whenever a
+drop of acid touches it, a frothy effervescence occurs. The drop of acid
+boils up and gives off the pungent odour of carbonic acid gas.
+
+The reason that calcite is hard to find in rocks is that percolating
+water, charged with acids, is constantly stealing it, and carrying it
+away into the ocean. The rocks that contain it crumble because the limy
+portions have been dissolved out.
+
+Some limestones resist the destructive action of water. When they are
+impregnated with silica they become transformed into marble, which takes
+a high polish like granite. Acids must be strong to make any impression
+on marble.
+
+The thick beds of pure limestone that underlie the surface soil in
+Kentucky and in parts of Virginia sometimes measure several hundred feet
+in thickness, a single stratum often being twenty feet thick. They are
+all horizontal, for they were formed on sea bottom, and have not been
+crumpled in later time. The dead bodies of sea creatures contributed
+their shells and skeletons to the lime deposit on the sea bottom. Who
+can estimate the time it took to form those thick, solid layers of lime
+rock? The animals were corals, crinoids, and molluscs. Little sand and
+clay show in the lime rock of this period, before the marshes of the
+Carboniferous Age took the place of the ancient inland sea of the
+Subcarboniferous Period, the sedimentary accumulations of which we are
+now talking about.
+
+The living corals one sees in the shallow water of the Florida coast
+to-day are building land by building up their limy skeletons. The reefs
+are the dead skeletons of past generations of these tiny living things.
+They take in lime from the water, and use it as we use lime in building
+our bones. In each case it is an unconscious process of animal
+growth--not a "building process" like a mason's building of a wall. Many
+people think that the coral polyp builds in this way. They give it
+credit for patience in a great undertaking. All the polyp does is to
+feed on whatever the water supplies that its digestive organs can use.
+It is like a sea anemone in appearance and in habits of life. It is not
+at all like an insect. Yet it is common to hear people speak of the
+"coral insect"! Do not let any one ever hear you repeat such a mistake.
+
+Southern Florida is made out of coral rock, but thinly covered with
+soil. It was made by the growth of reef after reef, and it is still
+growing.
+
+The Cretaceous Period of the earth's eventful history is named for the
+lime rock which we know as chalk. Beds of this recent kind of limestone
+are found in England and in France, pure white, made of the skeletons of
+the smallest of lime-consuming creatures, Foraminifera. They swarmed in
+deep water, and so did minute sponge animalcules and plant forms called
+Diatoms that took silica from the water, and formed their hard parts of
+this glassy substance. The result is seen in the nodules of flint found
+in the soft, snow-white chalk. Did you ever use a piece of chalk that
+scratched the black-board? The flint did it. Have you ever seen the
+chalk cliffs of Dover? When you do see them, notice how they gleam white
+in the sun. See how the rains have sculptured those cliffs. The
+prominences left standing out are strengthened by the flint they
+contain. Chalk beds occur in Texas and under our great plains; but the
+principal rocks of the age in America were sandstones and clays.
+
+
+
+
+THE AGE OF FISHES
+
+
+The first animal with a backbone recorded its existence among the
+fossils found in rocks of the upper Silurian strata. It is a fish; but
+the earliest fossils are very incomplete specimens. We know that these
+old-fashioned fishes were somewhat like the sturgeons of our rivers.
+Their bodies were encased in bony armour of hard scales, coated with
+enamel. The bones of the spine were connected by ball and socket joints,
+and the heads were movable. In these two particulars the fishes
+resembled reptiles. The modern gar-pike has a number of the same
+characteristics.
+
+Another backboned creature of the ancient seas was the ancestral type of
+the shark family. In some points this old-fashioned shark reminds us of
+birds and turtles. These early fishes foreshadowed all later
+vertebrates, not yet on the earth. After them came the amphibians, then
+the reptiles, then the birds, and latest the mammals.
+
+The race of fishes began, no doubt, with forms so soft-boned that no
+fossil traces are preserved in the rocks. When those with harder bones
+appeared, the fossil record began, and it tells the story of the passing
+of the early, unfish-like forms, and the coming of new kinds, great in
+size and in numbers, that swarmed in the seas, and were tyrants over all
+other living things. They conquered the giant straight-horns and
+trilobites, former rulers of the seas.
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+A sixteen-foot fossil fish from Cretaceous of Kansas, with a modern
+tarpon]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Ca�on Diablo meteorite from Arizona]
+
+One of these giant fishes fifteen to twenty feet long, three feet wide,
+had jaws two feet long, set with blade-like teeth. Devonian rocks in
+Ohio have yielded fine fossils of gigantic fishes and sharks.
+
+Devonian fishes were unlike modern kinds in these particulars, the
+spinal column extended to the end of the tail, whether the fins were
+arranged equally or unequally on the sides; the paired side fins look
+like limbs fringed with fins. Every Devonian fish of the gar type seems
+to have had a lung to help out its gill-breathing.
+
+In these traits the first fishes were much like the amphibians. They
+were the parent stock from which branched later the true fishes and the
+amphibians, as a single trunk parts into two main boughs. The trunk is
+the connecting link.
+
+The sea bottom was still thronged with crinoids, and lamp shells, and
+cup corals. Shells of both clam and snail shapes are plentiful. The
+chambered straight-horns are fewer and smaller, and coiled forms of this
+type of shell are found. Trilobite forms are smaller, and their numbers
+decrease.
+
+The first land plants appeared during this age. Ferns and giant club
+mosses and cycads grew in swampy ground. This was the beginning of the
+wonderful fern forests that marked the next age, when coal was formed.
+
+The rocks that bear the record of these living things in their fossils,
+form strata of great thickness that overlie the Silurian deposits. There
+is no break between them. So we understand that the sea changed its
+shore-line only when the Silurian deposits rose to the water-level.
+
+The Devonian sea was smaller than the Silurian. A great tract of
+Devonian deposits occupies the lower half of the state of New York,
+Canada between Lakes Erie and Huron, and the northern portions of
+Indiana and Illinois. These older layers of the stratified rock are
+covered with the deposits of later periods. Rivers that cut deep
+channels reveal the earlier rocks as outcrops along their canyon walk.
+The record of the age of fishes is, for the most part, still an unopened
+book. The pages are sealed, waiting for the geologist with his hammer to
+disclose the mysteries.
+
+
+
+
+KING COAL
+
+
+In this country, and in this age, who can doubt that coal is king? It is
+one of the few necessities of life. In various sections of the country,
+layers of coal have been discovered--some near the surface, others deep
+underground. These are the storehouses of fuel which the coal miners dig
+out and bring to the surface, and the railroads distribute. From
+Pennsylvania and Ohio to Alabama stretches the richest coal-basin.
+Illinois and Indiana contain another. From Iowa southward to Texas
+another broad basin lies. Central Michigan and Nova Scotia each has
+isolated coal-basins. All these have been discovered and mined, for they
+lie in the oldest part of the country.
+
+In the West, coal-beds have been discovered in several states, but many
+regions have not yet been explored. Vast coal-fields, still untouched,
+have been located in Alaska. The Government is trying to save this fuel
+supply for coming generations. Many of the richest coal-beds from Nova
+Scotia southward dip under the ocean. They have been robbed by the
+erosive action of waves and running water. Glaciers have ground away
+their substance, and given it to the sea. Much that remains intact must
+be left by miners on account of the difficulties of getting out coal
+from tilted and contorted strata.
+
+As a rule, the first-formed coal is the best. The Western coal-fields
+belong to the period following the Carboniferous Age. Although
+conditions were favourable to abundant coal formation, Western coal is
+not equal to the older, Eastern coal. It is often called _lignite_, a
+word that designates its immaturity compared with anthracite.
+
+Coal formed in the Triassic Period is found in a basin near Richmond,
+Virginia. There is an abundance of this coal, but it has been subjected
+to mountain-making pressure and heat, and is extremely inflammable. The
+miners are in constant danger on account of coal gas, which becomes
+explosive when the air of the shaft reaches and mingles with it. This
+the miner calls "fire damp." North Carolina has coal of the same
+formation, that is also dangerous to mine, and very awkward to reach, on
+account of the crumpling of the strata.
+
+There are beds of coal so pure that very little ash remains after the
+burning. Five per cent, of ash may be reasonably expected in pure coal,
+unmixed with sedimentary deposits. Such coal was formed in that part of
+the swamp which was not stirred by the inflow of a river. Wherever muddy
+water flowed in among the fallen stems of plants, or sand drifted over
+the accumulated peat, these deposits remained, to appear later and
+bother those who attempt to burn the coal.
+
+[Illustration: Eocene fish]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Trilobite from the Niagara limestone, Upper Silurian, of Western New
+York]
+
+[Illustration: Sigillaria, Stigmaria and Lepidodendron]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Coal fern]
+
+You know pure coal, that burns with great heat and leaves but little
+ashes. You know also the other kind, that ignites with difficulty, burns
+with little flame, gives out little heat, and dying leaves the furnace
+full of ashes. You are trying to burn ancient mud that has but a small
+proportion of coal mixed with it. The miners know good coal from poor,
+and so do the coal dealers. It is not profitable to mine the impure part
+of the vein. It costs as much to mine and ship as the best quality, and
+it brings a much lower price.
+
+The deeper beds of coal are better than those formed in comparatively
+recent time and found lying nearer the surface. In many bogs a layer of
+embedded root fibres, called peat, is cut into bricks and dried for
+burning. Deeper than peat-beds lie the _lignites_, which are old beds of
+peat, on the way to become coal. _Soft coal_ is older than lignite. It
+contains thirty to fifty per cent. of volatile matter, and burns
+readily, with a bright blaze. The richest of this bituminous coal is
+called _fat_, or _fusing coal_. The bitumen oozes out, and the coal
+cakes in burning. Ordinary soft coal contains less, but still we can see
+the resinous bitumen frying out of it as it burns. There is more heat
+and less volatile matter in _steam coal_, so-called because it is the
+fuel that most quickly forms steam in an engine. _Hard coal_ contains
+but five to ten per cent. of volatile matter. It is slow to ignite and
+burns with a small blue blaze.
+
+From peat to anthracite coal I have named the series which increases
+gradually in the amount of heat it gives out, and increases and then
+decreases in its readiness to burn and in the brightness of its flame.
+Anthracite coal has the highest amount of fixed carbon. This is the
+reason why it makes the best fuel, for fixed carbon is the substance
+which holds the store of imprisoned sunlight, liberated as heat when the
+coal burns. Tremendous pressure and heat due to shrinking of the earth's
+crust have crumpled and twisted the strata containing coal in eastern
+Pennsylvania, and thus changed bituminous coal into anthracite. Ohio
+beds, formed at the same time, but undisturbed by heat and pressure, are
+bituminous yet.
+
+The coal-beds of Rhode Island are anthracite, but the coal is so hard
+that it will not burn in an open fire. The terrible, mountain-making
+forces that crumpled these strata and robbed the coal of its volatile
+matter, left so little of the gas-forming element, that a very special
+treatment is necessary to make the carbon burn. It is used successfully
+in furnaces built for the smelting of ores.
+
+The last stage in the coal series is a black substance which we know as
+black lead, or graphite. We write with it when we use a "lead" pencil.
+This is anthracite coal after all of the volatile matter has been driven
+out of it. It cannot burn, although it is solid carbon. The beds of
+graphite have been formed out of coal by the same changes in the
+earth's crust which have converted soft coal into anthracite.
+
+The tremendous pressure that bears on the coal measures has changed a
+part of the carbon into liquid and gaseous form. Lakes of oil have been
+tapped from which jets of great force have spouted out. Such
+accumulations of oil usually fill porous layers of sandstone and are
+confined by overlying and underlying beds of impervious clay. Gas may be
+similarly confined until a well is drilled, relieving the pressure, and
+furnishing abundant or scanty supply of this valuable fuel. Western
+Pennsylvania coal-fields have beds of gas and oil. If mountain-making
+forces had broken the strata, as in eastern Pennsylvania, the gas and
+the oil would have been lost by evaporation.
+
+This is what happened in the anthracite coal-belt.
+
+
+
+
+HOW COAL WAS MADE
+
+
+The broad, rounded dome of a maple tree shades my windows from the
+intense heat of this August day. The air is hot, and every leaf of the
+tree's thatched roof is spread to catch the sunlight. The carbon in the
+air is breathed in through openings on the under side of each leaf. The
+sap in the leaf pulp uses the carbon in making starch. The sun's heat is
+absorbed. It is the energy that enables the leaf-green to produce a
+wonderful chemical change. Out of soil water, brought up from the roots,
+and the carbonic acid gas, taken in from the air, rich, sugary starch is
+manufactured in the leaf laboratory.
+
+This plant food returns in a slow current, feeding the growing cells
+under the bark, from leaf tip to root tip, throughout the growing tree.
+The sap builds solid wood. The maple tree has been built out of muddy
+water and carbon gas. It stands a miracle before our eyes. In its tough
+wood fibres is locked up all the heat its leaves absorbed from the sun,
+since the day the maple seed sprouted and the first pair of leaves
+lifted their palms above the ground.
+
+If my maple tree should die, and fall, and lie undisturbed on the
+ground, it would slowly decay. The carbon of its solid frame would pass
+back into the air, as gas, and the heat would escape so gradually that I
+could not notice it at all, unless I thrust my hand into the warm,
+crumbling mass.
+
+If my tree should be cut down to-day and chopped into stove wood, it
+would keep a fire in my grate for many months.
+
+Burning destroys wood substance a great deal faster than decay in the
+open air does, but the processes of rotting and burning are alike in
+this: each process releases the carbon, and gives it back to the air. It
+gives back also the sun's heat, stored while the tree was growing. There
+is left on the ground, and in the ashes on the hearth, only the mineral
+substance taken up in the water the roots gathered underground.
+
+If my tree stood in swampy ground and fell over under a high wind, the
+water that covered it and saturated its substance would prevent decay.
+The carbon would not be allowed to escape as a gas to the air; the woody
+substance would become gradually changed into _peat_. In this form it
+might remain for thousands of years, and finally be changed into coal.
+
+Whether it was burned while yet in the condition of peat, or millions of
+years later, when it was transformed into coal, the heat stored in its
+substance was liberated by the burning. The carbon and the heat went
+back to the air.
+
+Every green plant we see spreads its leaves to the sun. Every stick of
+wood we burn, and every lump of coal, is giving back, in the form of
+light and heat, the energy that came from sunshine and was captured by
+the green leaves. How long the wood has held this store of heat we may
+easily compute, for we can read the age of a tree. But the age of coal
+we cannot accurately state. The years probably should be counted by
+millions, instead of thousands.
+
+The great inland sea that covered the middle portion of the continent
+during the Silurian and the Devonian periods, became shallow by the
+deposit of vast quantities of sediment. Along the lines of the deposits
+of greatest thickness, a crumpling of the earth's crust lifted the first
+fold of the Alleghany Mountains as a great sea wall on the east, and on
+the western shore another formed the beginning of the Ozark Mountain
+system in Missouri. An island was lifted out of the sea, forming the
+elevated ground on which the city of Cincinnati now stands. Various
+other ridges and islands divided the ancient sea into much smaller
+bodies of water. Hemmed in by land these shallow sea-basins gradually
+changed into fresh-water lakes, for they no longer had connection with
+the ocean, and all the water they received came from rain. After
+centuries of freshets, and of filling in with the rock d�bris brought by
+the streams, they became great marshes, in which grew water-loving
+plants. Generation after generation of these plants died, and their
+remains, submerged by the water, were converted into peat. In the
+course of ages this peat became coal. This is the history of the coal
+measures.
+
+There is no guesswork here. The stems of plants do not lose their
+microscopic structure in all the ages it has taken to transform them to
+coal. A thin section of coal shows under a magnifier the structure of
+the stems of the coal-forming plants. Moreover, the veins of coal
+preserve above or below them, in shales that were once deposits of mud,
+the branching trunks of trees, perfectly fossilized. There are no better
+proofs of the vegetable origin of coal than the lumps themselves. But
+they are plain to the naked eye, while the coal tells its story to the
+man with the microscope.
+
+The fossil remains of the plants that flourished when coal was forming
+are gigantic, compared with plants of the same families now living. We
+must conclude that the climate was tropical, the air very heavy with
+moisture, and charged much more heavily than it is now with carbonic
+acid gas.
+
+These conditions produced, in rapid succession, forests of tree ferns
+and horsetails and giant club mosses. These are the three types of
+plants out of which the coal was made. They were all rich in resin,
+which makes the coal burn readily. The ferns had stems as large as tree
+trunks. Some have been found that are eighteen inches in diameter. We
+know they are ferns, because the leaves are found with their fruits
+attached to them in the manner of present-day ferns. The stems show the
+well known scar by which fern leaves are joined. And the wood of these
+fossil fern stems is tubular in structure, just as the wood of living
+ferns is to-day.
+
+Among the ferns which dominated these old marsh forests grew one kind,
+the scaly leaves of which covered the stems and bore their fruits on the
+branching tips. These giants, some of them with trunks four feet in
+diameter, belong to the same group of plants as our creeping club
+mosses, but in the ancient days they stood up among the other ferns as
+trees forty or fifty feet high.
+
+The giant scouring rushes, or horsetails, had the same general
+characteristics as the little reed-like plants we know by those names
+to-day.
+
+The highest plants of the coal period were leafy trees with nut-like
+fruits, that resemble the yew trees of the present. These gigantic trees
+were the first conifers upon the earth. They foreshadowed the pines and
+the other cone-bearing evergreens. Their leaves were broad and their
+fruits nut-like. The Japanese ginkgo, or maidenhair fern tree, is an
+old-fashioned conifer somewhat like those first examples of this family.
+Trunks sixty to seventy feet long, crowned with broad leaves and a spike
+of fruit, have been found lying in the upper layers of the coal-seams,
+and in sandstone strata that lie between the strata of coal. Peculiar
+circular discs, which the microscope reveals along the sides of the wood
+fibres of these fossil trees, prove the wood structure to be like that
+of modern conifers.
+
+Generation after generation of forests lived and died in the vast
+spreading swamps of this era. The land sank, and freshets came here and
+there, drowning out all plant life, and covering the layers of peat with
+beds of sand or mud. When the water went down, other forests took
+possession, and a new coal-bed was started. It is plainly seen that
+flooding often put an end to coal formation. Fifteen seams of coal, one
+above another, is the greatest number that have been found. The veins
+vary from one inch to forty feet in thickness. These are separated by
+layers of sandstone or shale, which accumulated as sediment, covering
+the stumps of dead tree ferns and other growths, and preserving them as
+fossils to tell the story of those bygone ages as plainly as any other
+record could have done.
+
+Fresh-water animals succeeded those of salt water in the swamps that
+formed the coal measures. Overhead, the first insects flitted among the
+branches of the tree ferns. Dragon-flies darted above the surface and
+dipped in water as they do to-day. Spiders, scorpions, and cockroaches,
+all air-breathing insects, were represented, but none of the higher,
+nectar-loving insects, like flies and bees and butterflies, were there.
+Flowering plants had not yet appeared on the earth. Snakelike
+amphibians, some fishlike, some lizard-like, and huge crocodilian forms
+appeared for the first time. These air-breathing swamp-dwellers could
+not have lived in salt water.
+
+Fresh-water molluscs and land shells appear for the first time as
+fossils in the rocks of the coal measures. On the shores of the ocean,
+the rocks of this period show that trilobites, horseshoe crabs, and
+fishes still lived in vast numbers, and corals continued to form
+limestone. The old types of marine animals changed gradually, but the
+coal measures show strikingly different fossils. These rocks bear the
+first record of fresh-water and land animals.
+
+
+
+
+THE MOST USEFUL METAL
+
+
+It is fortunate for us all that, out of the half-dozen so-called useful
+metals, iron, which is the most useful of them all to the human race,
+should be also the most plentiful and the cheapest. Aluminum is abundant
+in the common clay and soil under our feet. But separating it is still
+an expensive process; so that this metal is not commercially so
+plentiful as iron is, nor is it cheap.
+
+All we know of the earth's substance is based on studies of the
+superficial part of its crust, a mere film compared with the eight
+thousand miles of its diameter. Nobody knows what the core of the
+earth--the great globe under this surface film--is made of; but we know
+that it is of heavier material than the surface layer; and geologists
+believe that iron is an important element in the central mass of the
+globe.
+
+One thing that makes this guess seem reasonable is the great abundance
+of iron in the earth's crust. Another thing is that meteors which fall
+on the earth out of the sky prove to be chiefly composed of iron. All of
+their other elements are ones which are found in our own rocks. If we
+believe that the earth itself is a fragment of the sun, thrown off in a
+heated condition and cooling as it flew through space, we may consider
+it a giant meteor, made of the substances we find in the chance meteor
+that strikes the earth.
+
+Iron is found, not only in the soil, but in all plant and animal bodies
+that take their food from the soil. The red colour in fruits and
+flowers, and in the blood of the higher animals, is a form in which iron
+is familiar to us. It does more, perhaps, to make the world beautiful
+than any other mineral element known.
+
+But long before these benefits were understood, iron was the backbone of
+civilization. It is so to-day. Iron, transformed by a simple process
+into steel, sustains the commercial supremacy of the great civilized
+nations of the world. The railroad train, the steel-armoured battleship,
+the great bridge, the towering sky-scraper, the keen-edged tool, the
+delicate mechanism of watches and a thousand other scientific
+instruments--all these things are possible to-day because iron was
+discovered and has been put to use.
+
+It was probably one of the cave men, poking about in his fire among the
+rocks, who discovered a lump of molten metal which the heat had
+separated from the rest of the rocks. He examined this "clinker" after
+it cooled, and it interested him. It was a new discovery. It may have
+been he, or possibly his descendants, who learned that this metal could
+be pounded into other shapes, and freed by pounding from the pebbles
+and other impurities that clung to it when it cooled. The relics of
+iron-tipped spears and arrows show the skill and ingenuity of our early
+ancestors in making use of iron as a means of killing their prey. The
+earliest remains of this kind have probably been lost because the iron
+rusted away.
+
+Man was pretty well along on the road to civilization before he learned
+where iron could be found in beds, and how it could be purified for his
+use. We now know that certain very minute plants, which live in quiet
+water, cause iron brought into that water to be precipitated, and to
+accumulate in the bottom of these boggy pools. In ancient days these bog
+deposits of iron often alternated with coal layers. Millions of years
+have passed since these two useful substances were laid down. To-day the
+coal is dug, along with the bog iron. The coal is burned to melt the
+iron ore and prepare it for use. It is a fortunate region that produces
+both coal and iron.
+
+Bituminous coal is plentiful, and scattered all over the country, while
+anthracite is scarce. The cheapest iron is made in Alabama, which has
+its ore in rich deposits in hillsides, and coal measures close by,
+furnishing the raw material for coke. The result is that the region of
+Birmingham has become the centre of great wealth through the development
+of iron and coal mines.
+
+Where water flows over limestone rock, and percolates through layers of
+this very common mineral, it causes the iron, gathered in these rock
+masses, to be deposited in pockets. All along the Appalachian Mountains
+the iron has been gathered in beds which are being mined. These beds of
+ore are usually mixed with clay and other earthy substances from which
+the metal can be separated only by melting. The ore is thrown into a
+furnace where the metal melts and trickles down, leaving behind the
+non-metallic impurities. It is drawn off and run into moulds, where it
+cools in the form of "pig" iron.
+
+The first fuel used in the making of pig iron from the ore was charcoal.
+In America the early settlers had no difficulty in finding plenty of
+wood. Indeed, the forests were weeds that had to be cut down and burned
+to make room for fields of grain. The finding of iron ore always started
+a small industry in a colony. If there was a blacksmith, or any one else
+among the small company who understood working in iron, he was put in
+charge.
+
+To make the charcoal, wood was cut and piled closely in a dome-shaped
+heap, which was tightly covered with sods, except for a small opening
+near the ground. In this a fire was built, and smothered, but kept going
+until all the wood within the oven was charred.
+
+This fuel burned readily, with an intense heat, and without ashes.
+Sticks of charcoal have the form of the wood, and they are stiff enough
+to hold up the ore of iron so that it cannot crush out the fire. For a
+long time American iron was supplied by little smelters, scattered here
+and there. The workmen beat the melted metal on the forge, freeing it
+from impurities, and shaping the pure metal into useful articles.
+Sometimes they made it into steel, by a process learned in the Old
+World.
+
+The American iron industry, which now is one of the greatest in the
+world, centres in Pittsburg, near which great deposits of iron and coal
+lie close together. The making of coke from coal has replaced the
+burning of charcoal for fuel. When the forests were cut away by
+lumbermen, the supply of charcoal threatened to give out, and
+experiments were made in charring coal, which resulted in the successful
+making of coke, a fuel made from coal by a process similar to the making
+of charcoal from wood. The story of the making of coke out of hard and
+soft coal is a long one, for it began as far back as the beginning of
+the nineteenth century.
+
+In 1812 the first boat-load of anthracite coal was sent to Philadelphia
+from a little settlement along the Lehigh River. A mine had been opened,
+the owner of which believed that the black, shiny "rocks" would burn.
+His neighbours laughed at him, for they had tried building fires with
+them, and concluded that it could not be done. In Philadelphia, the
+owners of some coke furnaces gave the new fuel a trial, in spite of the
+disgust of the stokers, who thought they were putting out their fires
+with a pile of stones. After a little, however, the new fuel began to
+burn with the peculiar pale flame and intense heat that we know so
+well, and the stokers were convinced that here was a new fuel, with
+possibilities in it.
+
+But it was hard for people to be patient with the slow starting of this
+hard coal. Not until 1840 did it come into general favour, following the
+discovery that if hot air was supplied at the draught, instead of cold,
+anthracite coal became a perfect fuel.
+
+At Connellsville, Pennsylvania, a vein of coal was discovered which made
+coke of the very finest quality. Around this remarkable centre, coke
+ovens were built, and iron ore was shipped in, even from the rich beds
+of the Lake Superior country. But it was plain to see that Connellsville
+coal would become exhausted; and so experiments in coke-making from
+other coals were still made. When soft coal burns, a waxy tar oozes out
+of it, which tends to smother the fire. Early experiments with coal in
+melting iron ore indicated that soft coal was useless as a substitute
+for charcoal and coke; but later experiments proved that coke of fine
+quality can be made out of this bituminous soft coal, by drawing off the
+tar which makes the trouble. New processes were invented by which
+valuable gas and coal tar are taken out of bituminous coal, leaving, as
+a residue, coke that is equal in quality to that made from the
+Connellsville coal. Fortunes have been made out of the separation of the
+elements of the once despised soft coal. For the coke and each of its
+by-products, coal tar and coal gas, are commercial necessities of life.
+
+The impurities absorbed by the melting iron ore include carbon,
+phosphorus, and silicon. Carbon is the chief cause of the brittleness of
+cast iron. The puddling furnace was invented to remove this trouble. The
+melted ore was stirred on a broad, basin-like hearth, with a
+long-handled puddling rake. The flames swept over the surface, burning
+the carbon liberated by the stirring. It was a hard, hot job for the man
+at the rake, but it produced forge iron, that could be shaped, hot or
+cold, on the anvil.
+
+The next improvement was the process of pressing the hot iron between
+grooved rollers to rid it of slag and other foreign matters collected in
+the furnace. The old way was to hammer the metal free from such
+impurities. This was slow and hard work.
+
+Iron was an expensive and scarce metal until the hot blast-furnace
+cheapened the process of smelting the ore. The puddling furnace and the
+grooved rollers did still more to bring it into general use. The
+railroads developed with the iron industry. Soon they required a metal
+stronger than iron. Steel was far too expensive, though it was just what
+was needed. Efforts were made to find a cheap way to change iron into
+steel. Sir Henry Bessemer solved the problem by inventing the Bessemer
+converter. It is a great closed retort, which is filled with melted pig
+iron. A draught admits air, and the carbon is all burned out. Then a
+definite amount of carbon, just the amount required to change iron into
+steel, is added, by throwing in bars of an alloy of carbon and
+manganese. The latter gives steel its toughness, and enables it to
+resist greater heat without crystallizing and thus losing its temper.
+
+When the carbon has been put in, the retort is closed. The molten metal
+absorbs the alloy, and the product is Bessemer steel. In fifteen minutes
+pig iron can be transformed into ingot steel. The invention made
+possible the use of steel in the construction of bridges, high
+buildings, and ships. It made this age of the world the Age of Steel.
+
+
+
+
+THE AGE OF REPTILES
+
+
+Two big and interesting reptiles we see in the Zoo, the crocodile and
+its cousin, the alligator. In the everglades of Florida both are found.
+The crocodile of the Nile is protected by popular superstition, so it is
+in better luck than ours. The alligators have been killed off for their
+skins, and it is only a matter of time till these lumbering creatures
+will be found only in places where they are protected as the remnants of
+a vanished race. Giant reptiles of other kinds are few upon the earth
+now. The _boa constrictor_ is the giant among snakes. The great tropical
+turtles represent an allied group. Most of the turtles, lizards, and
+snakes are small, and in no sense dominant over other creatures.
+
+The rocks that lie among the coal measures contain fossils of huge
+animals that lived in fresh water and on land, the ancestors of our
+frogs, toads, and salamanders, a group we call amphibians. Some of these
+animals had the form of snakes; some were fishlike, with scaly bodies;
+others were lizard-like or like huge crocodiles. These were the
+ancestors of the reptiles, which became the rulers of land and sea
+during the Mesozoic Era. The rocks that overlie the coal measures
+contain fossils of these gigantic animals.
+
+Strange crocodile-like reptiles, with turtle-like beaks and tusks, but
+no teeth, left their skeletons in the mud of the shores they frequented.
+And others had teeth in groups--grinders, tearers, and cutters--like
+mammals. These had other traits like the old-fashioned, egg-laying
+mammals, the duck-billed platypus, for example, that is still found in
+Australia. Along with the remains of these creatures are found small
+pouched mammals, of the kangaroo kind, in the rocks of Europe and
+America. These land animals saw squatty cycads, and cone-bearing trees,
+the ancestors of our evergreens, growing in forests, and marshes covered
+with luxuriant growths of tree ferns and horsetails, the fallen bodies
+of which formed the recent coal that is now dug in Virginia and North
+Carolina. Ammonites, giant sea snails, with chambered shells that
+reached a yard and more in diameter, and gigantic squids, swam the seas.
+Sea urchins, starfish, and oysters were abundant. Insects flitted
+through the air, but no birds appeared among the trees or beasts in the
+jungles. Over all forms of living creatures reptiles ruled. They were
+remarkable in size and numbers. There were swimming, running, and flying
+forms.
+
+[Illustration: Banded sandstone from Calico Ca�on, South Dakota]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Opalized wood from Utah]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Restoration of a carnivorous Dinosaur, Allosaurus, from the Upper
+Jurassic and Lower Cretaceous of Wyoming. When erect the animal was
+about 15 feet high]
+
+The fish-reptile, _Ichthyosaurus_, was a hump-backed creature, thirty to
+forty feet long, with short neck, very large head, and long jaw, set
+with hundreds of pointed teeth. Its eye sockets were a foot across. The
+four short limbs were strong paddles, used for swimming. The long,
+slender tail ended in a flat fin. Perfect skeletons of this creature
+have been found. Its rival in the sea was the lizard-like
+_Plesiosaurus_, the small head of which was mounted on a long neck. The
+tail was short, but the paddles were long and powerful. No doubt this
+agile creature held its own, though somewhat smaller than the more
+massively built Ichthyosaurus.
+
+The land reptiles called _Dinosaurs_ were the largest creatures that
+have ever walked the earth. In the American Museum of Natural History,
+in New York, the mounted skeleton of the giant Dinosaur fairly takes
+one's breath away. It is sixty-six feet long, and correspondingly large
+in every part, except its head. This massive creature was remarkably
+short of brains.
+
+The strangest thing about the land reptiles is the fact that certain of
+them walked on their hind legs, like birds, and made three-toed tracks
+in the mud. Indeed, these fossil tracks, found in slate, were called
+bird tracks, until the bones of the reptile skeleton with the bird-like
+foot were discovered. Certain long grooves in the slate, hitherto
+unexplained, were made by the long tail that dragged in the mud.
+
+When the mud dried, and was later covered with sediment of another kind,
+these prints were preserved, and when the bed of rock was discovered by
+quarrymen, the two kinds split apart, showing the record of the stroll
+of a giant along the river bank in bygone days.
+
+The flying reptiles were still more bird-like in structure, though
+gigantic in size. Imagine the appearance of a great lizard with
+bat-like, webbed wings and bat-like, toothed jaws! The first feathered
+fossil bird was discovered in the limestone rock of Bavaria. It was a
+wonderfully preserved fossil, showing the feathers perfectly. Three
+fingers of each "hand" were free and clawed, so that the creature could
+seize its prey, and yet use its feathered wings in flight. The small
+head had jaws set with socketed teeth, like a reptile's, and the long,
+lizard tail of twenty-one bones had a pair of side feathers at each
+joint. This _Archeopteryx_ is the reptilian ancestor of birds. During
+this age of the world, one branch of the reptile group established the
+family line of birds. The bird-like reptiles are the connecting link
+between the two races. How much both birds and reptiles have changed
+from that ancient type, their common ancestor!
+
+I have mentioned but a few of the types of animals that make the
+reptilian age the wonder of all time. One after another skeletons are
+unearthed and new species are found. The Connecticut River Valley, with
+its red sandstones and shales of the Mesozoic Era, is famous among
+geologists, because it preserves the tracks of reptiles, insects, and
+crustaceans. These signs tell much of the life that existed when these
+flakes of stone were sandy and muddy stretches Not many bones have been
+found, however. The thickness of these rocks is between one and two
+miles. The time required to accumulate so much sediment must have been
+very great.
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Model of a three-horned Dinosaur, _Triceratops_, from Cretaceous of
+Montana. Animal in life about 25 feet long]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Mounting the forelegs of _Brontosaurus_, the aquatic Dinosaur]
+
+It is not clear just what caused the race of giant reptiles to decline
+and pass away. The climate did not materially change. Perhaps races grow
+old, and ripe for death, after living long on the earth. It seems as if
+their time was up; and the clumsy giants abdicated their reign, leaving
+dominion over the sea, the air, and the land to those animals adapted to
+take the places they were obliged to vacate.
+
+
+
+
+THE AGE OF MAMMALS
+
+
+The warm-blooded birds and mammals followed the reptiles. This does not
+mean that all reptiles died, after having ruled the earth for thousands
+of years. It means that changes in climate and other life conditions
+were unfavourable to the giants of the cold-blooded races, and gradually
+they passed away. They are represented now on the earth by lesser
+reptiles, which live comfortably with the wild creatures of other
+tribes, but which in no sense rule in the brute creation. They live
+rather a lurking, cautious life, and have to hide from enemies, except a
+few more able kinds, provided with means of defense.
+
+There were mammals on the earth in the days of reptilian supremacy, but
+they were small in size and numbers, and had to avoid any open conflict
+with the giant reptiles, or be worsted in a fight. Now the time came
+when the ruling power changed hands. The mammals had their turn at
+ruling the lower animals. It was the beginning of things as they are
+to-day, for mammals still rule. But many millions of years have probably
+stood between the age when this group of animals first began to swarm
+over the earth, and the time when Man came to be ruler over all created
+things.
+
+Among the reptiles of the period when the sea, the land, and the air
+were swarming with these great creatures were certain kinds that had
+traits of mammals. Others were bird-like. From these reptilian ancestors
+birds and mammals have sprung. No one doubts this. The fossils prove it,
+step by step.
+
+Yet the rocks surprise the geologist with the suddenness with which many
+new kinds of mammals appeared on the earth. Possibly the rocks
+containing the bones of so many kinds were fortunately located. The
+spots may have been morasses where migrating mammals were overwhelmed
+while passing. Possibly conditions favored the rapid development of new
+kinds, and the multiplication of their numbers. Warm, moist climate
+furnished abundant succulent plant food for the herbivors, and these in
+turn furnished prey for the carnivors.
+
+The coal formed during the Tertiary Period gives added proof that the
+plant life was luxuriant. The kinds of trees that grew far north of our
+present warm zones have left in the rocks evidence in the form of
+perfect leaves and cones and other fruits. For instance, magnolias grew
+in Greenland, and palm trees in Dakota. The temperature of Greenland was
+thirty degrees warmer than it is now. Our Northern States lie in a belt
+that must have had a climate much like that of Florida now. Europe was
+correspondingly mild.
+
+A special chapter tells of the gradual development of the horse. One
+hundred different kinds of mammals have been found in the Eocene rocks,
+many of which have representative species at the same time in Europe and
+America. The rocks of Asia probably have similar records.
+
+The Eocene rocks, lowest of the Tertiary strata, contain remains of
+animals the families of which are now extinct. Next overlying the
+Eocene, the Miocene rocks have fossils of animals belonging to modern
+families--rhinoceroses, camels, deer, dogs, cats, horses--but the genera
+of which are now extinct. The Pliocene strata (above the Miocene)
+contains fossils of animals so closely related to the wild animals now
+on the earth as to belong to the same genera. They differ from modern
+kinds only in the species, as the red squirrel is a different species
+from the gray.
+
+So the record in the rocks shows a gradual approach of the mammals to
+the kinds we know, a gradual passing of the mighty forms that ruled by
+size and strength, and the coming of forms with greater intelligence,
+adapted to the change to a colder climate.
+
+It sometimes happens that a farmer, digging a well on the prairie,
+strikes the skeleton of a monster mammal, called the _mastodon_. This
+very thing happened on a neighbour's farm when I was a girl, in Iowa.
+Everybody was excited. The owner of the land dug out every bone, careful
+that the whole skeleton be found. As he expected, the director of a
+museum was glad to pay a high price for the bones.
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Restoration of an aquatic Dinosaur, _Brontosaurus excelsus_, from the
+Upper Jurassic and Lower Cretaceous of Wyoming. The animal in life was
+over 60 feet long]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Restoration of the small carnivorous Dinosaur, _Ornitholestes hermanui_,
+catching a primitive bird _Arch�opteryx_. Upper Jurassic and Lower
+Cretaceous]
+
+The mastodon was about the size of an elephant, with massive limbs, and
+large, heavy head that bore two stout, up-curved tusks of ivory. The
+creature moved in herds like the buffalo from swamp to swamp; and old
+age coming on, the individual, unable to keep up with the herd, sank to
+his death in the boggy ground. The peat accumulated over his bones,
+undisturbed until thousands of years elapse, and the chance digging of a
+well discovers his skeleton.
+
+Frozen in the ice of northern Siberia, near the mouths of rivers, a
+number of mammoths have been found. These are creatures of the elephant
+family, and belonging to the extinct race that lived in the Quaternary
+Period, just succeeding the Tertiary. The ice overtook the specimens,
+and they have been in cold storage ever since. For this reason, both
+flesh and bones are preserved, a rare thing to happen, and rarer still
+to be seen by a scientist.
+
+The ignorant natives made a business of watching the ice masses at the
+river mouth for dark spots that showed where a mammoth was encased in
+the ice. If an iceberg broke off near such a place, the sun might thaw
+the ice front of the glacier, until the hairy monster could at length be
+reached. His long hair served for many uses, and the wool that grew
+under the hair was used as a protection from the Arctic winter. The
+frozen flesh was eaten; the bones carved into useful tools; but the
+chief value of the find was in the great tusks of ivory, that curved
+forward and pointed over the huge shoulders. It was worth a fortune to
+get a pair and sell them to a buyer from St. Petersburg.
+
+One of the finest museum specimens of the mammoth was secured by buying
+the tusks of the dealer, and by his aid tracing the location of the
+carcass, which was found still intact, except that dogs had eaten away
+part of one foreleg, bone and all. From this carefully preserved
+specimen, models have been made, exactly copying the shape and the size
+of the animal, its skin, hair, and other details.
+
+The sabre-toothed tiger, the sharp tusks of which, six to eight inches
+long, made it a far more ferocious beast than any modern tiger of
+tropical jungles, was a Quaternary inhabitant of Europe and America. So
+was a smaller tiger, and a lion. The Irish elk, which stood eleven feet
+high, with antlers that spread ten feet apart at the tips, was monarch
+in the deer family, which had several different species on both
+continents. Wild horses and wild cattle, one or two of great size,
+roamed the woods, while rhinos and the hippopotamus kept near the
+water-courses. Hyenas skulked in the shadows, and acted as scavengers
+where the great beasts of prey had feasted. Sloths and cuirassed
+animals, like giant armadillos, lived in America. Among bears was one,
+the cave bear, larger than the grizzly. True monkeys climbed the trees.
+Flamingo, parrots, and tall secretary birds followed the giant
+_gastornis_, the ancestor of wading birds and ostriches, which stood ten
+feet high, but had wings as small and useless as the auk of later times.
+
+With the entrance of the modern types of trees, came other flowering
+plants, and with them the insects that live on the nectar of flowers.
+Through a long line of primitive forms, now extinct, flowering plants
+and their insect friends conform to modern types. The record is written
+in the great stone book.
+
+The Age of Mammals in America and Europe ended with the gradual rise of
+the continental areas, and a fall of temperature that ushered in the Ice
+Age. With the death of tropical vegetation, the giant mammals passed
+away.
+
+
+
+
+THE HORSE AND HIS ANCESTORS
+
+
+Every city has a horse market, where you may look over hundreds of
+animals and select one of any colour, size, or kind. The least in size
+and weight is the Shetland pony, which one man buys for his children to
+drive or ride. Another man wants a long-legged, deep-chested hunter.
+Another wants heavy draught-horses, with legs like great pillars under
+them, and thick, muscular necks--horses weighing nearly a ton apiece and
+able to draw the heaviest trucks. What a contrast between these slow but
+powerful animals and the graceful, prancing racer with legs like
+pipe-stems--fleet and agile, but not strong enough to draw a heavy load!
+
+All these different breeds of horses have been developed since man
+succeeded in capturing the wild horse and making it help him. Man
+himself was still a savage, and he had to fight with wild beasts, as if
+he were one of them, until he discovered that he could conquer them by
+some power higher than physical strength. From this point on, human
+intelligence has been the power that rules the lower animals. Its
+gradual development is the story of the advance of civilization on the
+earth. Through unknown thousands of years it has gone on, and it is not
+yet finished.
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Restoration of a Siberian mammoth, _Elephas primogenius_, pursued by men
+of the old stone age of Europe. Late Pleistocene epoch]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Restoration of a small four-toed ancestor of the horse family, _Eohippus
+venticolus_. Lower Eocene of Wyoming]
+
+Just when and where and how our savage ancestors succeeded in taming the
+wild horse of the plains and the forests of Europe or Asia is unknown.
+Man first made friends with the wild sheep, which were probably more
+docile than wild oxen and horses. We can imagine cold and hungry men
+seeking shelter from storms in rocky hollows, where sheep were huddled.
+How warm the woolly coats of these animals felt to their human
+fellow-creatures crowded in with them in the dark!
+
+It is believed that the primitive men who used stone axes as implements
+and weapons, learned to use horses to aid them in their hunting, and in
+their warfare with beasts and other men. Gradually these useful animals
+were adapted to different uses; and at length different breeds were
+evolved. Climate and food supply had much to do with the size and the
+character of the breeds. In the Shetland Islands the animals are
+naturally dwarfed by the cold, bleak winters, and the scant vegetation
+on which they subsist. In middle Europe, where the summers are long and
+the winters mild, vegetation is luxurious, and the early horses
+developed large frames and heavy muscles. The Shetland pony and the
+Percheron draught-horse are the two extremes of size.
+
+What man has done in changing the types of horses is to emphasize
+natural differences. The offspring of the early heavy horses became
+heavier than their parents. The present draught-horse was produced,
+after many generations, all of which gradually approached the type
+desired. The slender racehorses, bred for speed and endurance rather
+than strength, are the offspring of generations of parents that had
+these qualities strongly marked. Hence came the English thoroughbred and
+the American trotter.
+
+We can read in books the history of breeds of horses. Our knowledge of
+what horses were like in prehistoric times is scant. It is written in
+layers of rock that are not very deep, but are uncovered only here and
+there, and only now and then seen by eyes that can read the story told
+by fossil skeletons of horses of the ages long past.
+
+Geologists have unearthed from time to time skeletons of horses. It was
+Professor Marsh who spent so much time in studying the wonderful beds of
+fossil mammals in the western part of this country, and found among them
+the skeletons of many species of horses that lived here with camels and
+elephants and rhinoceroses and tigers, long before the time of man's
+coming.
+
+How can any one know that these bones belonged to a horse's skeleton?
+Because some of them are like the bones of a modern horse. It is an easy
+matter for a student of animal anatomy to distinguish a horse from a cow
+by its bones. The teeth and the foot are enough. These are important and
+distinguishing characters. It is by peculiarities in the formation of
+the bones of the foot that the different species of extinct horses are
+recognized by geologists.
+
+Wild horses still exist in the wilds of Russia. Remains of the same
+species have been dug out of the soil and found in caves in rocky
+regions. Deeper in the earth are found the bones of horses differing
+from those now living. The bones of the foot indicate a different kind
+of horse--an unknown species. But in the main features, the skeleton is
+distinctly horse-like.
+
+In rocks of deeper strata the fossil bones of other horses are found.
+They differ somewhat from those found in rocks nearer the surface of the
+earth, and still more from those of the modern horse. The older the
+rocks, the more the fossil horse differs from the modern. Could you
+think of a more interesting adventure than to find the oldest rocks that
+show the skeletons of horses?
+
+The foot of a horse is a long one, though we think of it as merely the
+part he walks on. A horse walks on the end of his one toe. The nail of
+the toe we call the "hoof." The true heel is the hock, a sharp joint
+like an elbow nearly half way up the leg. Along each side of the cannon,
+the long bone of this foot, lies a splint of bone, which is the remnant
+of a toe, that is gradually being obliterated from the skeleton. These
+two splints in the modern horse's foot tell the last chapter of an
+interesting story. The earliest American horse, the existence of which
+is proved by fossil bones, tells the first chapter. The story has been
+read backward by geologists. It is told by a series of skeletons, found
+in successive strata of rock.
+
+The "Bad Lands" of the arid Western States are rich in fossil remains of
+horses. Below the surface soil lie the rocks of the Quaternary Period,
+which included the drift laid down by the receding glaciers and the
+floods that followed the melting of the ice-sheet. Under the Quaternary
+lie the Tertiary rocks. These comprise three series, called the Eocene,
+Miocene, and Pliocene, the Eocene being the oldest. In the middle region
+of North America, ponds and marshy tracts were filled in during the
+Tertiary Period, by sediment from rivers; and in these beds of clay and
+other rock d�bris the remains of fresh-water and land animals are
+preserved. Raised out of water, and exposed to erosive action of wind
+and water, these deposits are easily worn away, for they have not the
+solidity of older rocks. They are the crumbly Bad Lands of the West, cut
+through by rivers, and strangely sculptured by wind and rain. Here the
+fossil horses have been found.
+
+_Eohippus_, the dawn horse, is the name given a skeleton found in 1880
+in the lower Eocene strata in Wyoming. This specimen lay buried in a
+rock formation ages older than that in which the oldest known skeleton
+of this family had been found. Its discovery made a great sensation
+among scientists. This little animal, the skeleton of which is no larger
+than that of a fox, had four perfect toes, and a fifth splint on the
+forefoot, and three toes on the hind foot. The teeth are herbivorous.
+
+_Orohippus_, with a larger skeleton, was found in the middle Eocene
+strata of Wyoming. Its feet are like those of its predecessor, except
+that the splint is gone. The teeth as well as the feet are more like
+those of the modern horse.
+
+_Mesohippus_, the three-toed horse, found in the Miocene, shows the
+fourth toe reduced to splints, and the skeleton as big as that of a
+sheep. In this the horse family becomes fairly established.
+
+_Hypohippus_, the three-toed forest horse, found in the middle Miocene
+strata of Colorado, is a related species, but not a direct ancestor of
+the modern horse.
+
+_Neohipparion_, the three-toed desert horse, from the upper Miocene
+strata, shows the three toes still present. But the Pliocene rocks
+contain fossils showing gradual reduction of the two side toes,
+modification of the teeth, and increase in size of the skeleton.
+
+_Protohippus_ and _Pliohippus_, the one-toed species from the Pliocene
+strata, illustrate these changes. They were about the size of small
+ponies.
+
+_Equus_, the modern horse, was represented in the Pliocene strata by a
+species, now extinct, called _Equus Scotti_. This we may regard as the
+true wild horse of America, for it was as large as the domesticated
+horse, and much like it, though more like a zebra in some respects. No
+one can tell why these animals, once abundant in this country, became
+extinct at the end of the Tertiary Period. But this is undoubtedly true.
+
+The types described form a series showing how the ancestors of the
+modern horse, grazing on the marshy borders of ancient ponds, lived and
+died, generation after generation, through a period covering thousands,
+possibly millions, of years. Along the sides of the crumbling buttes
+these ancient burying-grounds are being uncovered. Within a dozen years
+several expeditions, fitted out by the American Museum of Natural
+History, have searched the out-cropping strata in Dakota and Wyoming for
+bones of mammals known to have lived at the time the strata were forming
+in the muddy shallows along the margins of lake and marsh. Duplicate
+skeletons of the primitive horse types above have been found, and vast
+numbers of their scattered bones. Each summer geological excursions will
+add to the wealth of fossils of this family collected in museums.
+
+The Tertiary rocks in Europe yield the same kind of secrets. The region
+of Paris overlies the estuary of an ancient river. When the strata are
+laid bare by the digging of foundations for buildings, bones are found
+in abundance. Cuvier was a famous French geologist who made extensive
+studies of the remains of the prehistoric animals found in this old
+burial-place called by scientists the Paris basin. He believed that the
+dead bodies floated down-stream and accumulated in the mud of the
+delta, where the tide checked the river's current.
+
+Skeletons of the Hipparion, a graceful, three-toed horse, were found in
+numbers in the strata of the Miocene time. This animal lived in Europe
+while the Pliohippus and the Protohippus were flourishing in America.
+
+A great number of species of tapir-like animals left their bones in the
+Paris basin, among them a three-hoofed animal which may have been the
+connecting link between the horse and the tapir families. Cuvier found
+the connecting link between tapirs and cud-chewing mammals.
+
+
+
+
+THE AGE OF MAN
+
+
+The hairy, woolly mammoth was one of the giant mammals that withstood
+the cold of the great ice flood, when the less hardy kinds were cut off
+by the changing climate of the northern half of Europe and America. In
+caves where the wild animals took refuge from their enemies, skeletons
+of men have been found with those of the beasts. With these chance
+skeletons have been found rude, chipped stone spear-heads, hammers, and
+other tools. With these the savage ancestors of our race defended
+themselves, and preyed on such animals as they could use for food. They
+hunted the clumsy mammoth successfully, and shared the caverns in the
+rocks with animals like the hyena, the sabre-toothed tiger, and the cave
+bear, which made these places their homes. In California a human skull
+was found in the bed of an ancient river, which was buried by a lava
+flow from craters long ago extinct. With this buried skull a few
+well-shaped but rough stone tools were found. This man must have lived
+when the great ice flood was at its height.
+
+In southern France, caves have been opened that contained bones and
+implements of men who evidently lived by fishing and hunting. Bone
+fish-hooks showed skill in carving with the sharp edges of flint
+flakes. A spirited drawing of a mammoth, made on a flat, stone surface,
+is a proof that savage instincts were less prominent in these cave men
+than in those who fought the great reindeer and the mammoth farther
+north.
+
+In later times men of higher intelligence formed tribes, tamed the wild
+horse, the ox, and the sheep, and made friends with the dog. Great heaps
+of shells along the shores show where the tribes assembled at certain
+times to feast on oysters and clams. Bones of animals used as food, and
+tools, are found in these heaps, called "kitchen-middens." These are
+especially numerous in Northern Europe. The stone implements used by
+these tribes were smoothly polished. A higher intelligence expressed
+itself also by the making of utensils out of clay. This pottery has been
+found in shell heaps. So the rude cave man, who was scarcely less a wild
+beast than the animals which competed with him for a living and a
+shelter from storms and cold, was succeeded by a higher man who brought
+the brutes into subjection by force of will and not by physical
+strength.
+
+The lake-dwellers, men of the Bronze Age, built houses on piles in the
+lakes of Central Europe. About sixty years ago the water was low, and
+these relics of a vanished race were first discovered. The lake bottoms
+were scraped for further evidences of their life. Tools of polished
+stone and of bronze were taken up in considerable numbers. Stored
+grains and dried fruits of several kinds were found. Ornamental
+trinkets, weapons of hunters and warriors, and agricultural tools tell
+how the people lived. Their houses were probably built over the water as
+a means of safety from attack of beasts or hostile men.
+
+In our country the mound-builders have left the story of their manners
+of life in the spacious, many-roomed tribal houses, built underground,
+and left with a great variety of relics to the explorers of modern
+times. These people worked the copper mines, and hammered and polished
+lumps of pure metal into implements for many uses. With these are tools
+of polished stone. Stores of corn were found in many mounds scattered in
+the Mississippi Valley.
+
+The cliff-dwellers of the mesas of Arizona and New Mexico had habits
+like those of the mound-builders, and the Aztecs, a vanished race in the
+Southwest, at whose wealth and high civilization the invading Spaniards
+under Cortez marvelled. The plastered stone houses of the cliff-dwelling
+Indians had many stories and rooms, each built to house a tribe, not
+merely a family.
+
+The Pueblo, the Moqui, and the Zuni Indians build similar dwellings
+to-day, isolated on the tops of almost inaccessible mesas.
+
+Millions of years have passed since life appeared on the earth.
+Gradually higher forms have followed lower ones in the sea and on the
+land. But not all of the lower forms have gone. All grades of plants
+and animals still flourish, but the dominant class in each age is more
+highly organized than the class that ruled the preceding age.
+
+To discover the earth's treasure, and to turn it to use; to tame wild
+animals and wild plants, and make them serve him; to create ever more
+beautiful and more useful forms in domestication; to find out the
+earth's life story, by reading the pages of the great stone book--these
+are undertakings that waited for man's coming.
+
+       *       *       *       *       *
+
+
+
+
+PART II
+
+THE SKY
+
+       *       *       *       *       *
+
+
+
+
+EVERY FAMILY A "STAR CLUB"
+
+
+The best family hobby we have ever had is the stars. We have a star club
+with no dues to pay, no officers to boss us, and only three rules:
+
+1. We shall have nothing but "fun" in this club--no hard work. Therefore
+no mathematics for us!
+
+2. We can't afford a telescope. Therefore we must be satisfied with what
+bright eyes can see.
+
+3. No second-hand wonders for us! We want to see the things ourselves,
+instead of depending on books.
+
+You can't imagine what pleasure we have had in one short year! The baby,
+of course, was too young to learn anything, and besides he was in bed
+long before the stars came out. But Ruth, our seven-year-old, knows ten
+of the fifteen brightest stars; and she can pick out twelve of the most
+beautiful groups or constellations. We grown-ups know all of the
+brightest stars, and all forty-eight of the most famous constellations.
+And the whole time we have given to it would not exceed ten minutes a
+day!
+
+And the best part is the _way_ we know the stars. The sky is no longer
+bewildering to us. The stars are not cold, strange, mysterious. They are
+friends. We know their faces just as easily as you know your playmates.
+For instance, we know Sirius, because he is the brightest. We know
+Castor and Pollux, because they are twins. We know Regulus, because he
+is in the handle of the Sickle. And some we know by their colours. They
+are just as different as President Taft, "Ty" Cobb, Horace Fletcher and
+Maude Adams. And quite as interesting!
+
+What's more, none of us can ever get lost again. No matter what strange
+woods or city we go to, we never get "turned around." Or if we do, we
+quickly find the right way by means of the sun or the stars.
+
+Then, too, our star club gives us all a little exercise when we need it
+most. Winter is the time when we all work hardest and have the fewest
+outdoor games. Winter is also the best time for young children to enjoy
+the stars, because it gets dark earlier in winter--by five o'clock, or
+long before children go to bed. It is pleasant to go out doors for half
+an hour before supper and learn one new star or constellation.
+
+Again, it is always entertaining because every night you find the old
+friends in new places. No two nights are just the same. The changes of
+the moon make a great difference. Some nights you enjoy the moonlight;
+other nights you wish there were no moon, because it keeps you from
+spying out some new star. We have a little magazine that tells us all
+the news of the stars and the planets and the comets _before_ the things
+happen! We pay a dollar a year for it. It is called the _Monthly
+Evening Sky Map_.
+
+When we first became enthusiastic about stars, the father of our family
+said: "Well, I think our Star Club will last about two years. I judge it
+will cost us about two dollars and we shall get about twenty dollars
+worth of fun out of it." But in all three respects father was mistaken.
+
+Part of the two dollars father spoke of went for a book called "The
+Friendly Stars," and seventy-five cents we spent for the most
+entertaining thing our family ever bought--a planisphere. This is a
+device which enables us to tell just where any star is, at any time, day
+or night, the whole year. It has a disc which revolves. All we have to
+do is to move it until the month and the day come right opposite the
+very hour we are looking at it, and then we can tell in a moment which
+stars can be seen at that time. Then we go down the street where there
+is a good electric light at the corner and we hold our planisphere up,
+almost straight overhead. The light shines through, so that we can read
+it, and it is just as if we had a map of the heavens. We can pick out
+all the interesting constellations and name them just as easily as we
+could find the Great Lakes or Rocky Mountains in our geography.
+
+We became so eager not to miss any good thing that father got another
+book. Every birthday in our family brought a new star book, until now we
+have about a dozen--all of them interesting and not one of them having
+mathematics that children cannot understand. So I think we have spent on
+stars fifteen dollars more than we needed to spend (but I'm glad we did
+it), and I think we have had about two hundred dollars worth of fun!
+Yes, when I think what young people spend on ball games, fishing,
+tennis, skating, and all the other things that children love, I am sure
+our family has had about two hundred dollars worth of fun out of stars.
+And there is more to come!
+
+You would laugh to know why I enjoy stars so much. I have always studied
+birds and flowers and trees and rocks and shells so much that I was
+afraid to get interested in stars. I thought it wouldn't rest me. But
+it's a totally different kind of science from any I ever studied! There
+are no families, genera, and species among the stars, thank Heaven!
+That's one reason they refresh me. Another is that no one can press them
+and put them in a herbarium, or shoot them and put them in a museum. And
+another thing about them that brings balm to my spirit is that no human
+being can destroy their beauty. No one can "sub-divide" Capella and fill
+it with tenements. No one can use Vega for a bill-board. Ah, well! we
+must not be disturbed if every member of our family has a different
+point of view toward the stars; we can all enjoy and love them in our
+own ways.
+
+How would you like to start a Star Club like ours? You ought to be able
+to persuade your family to form one, because it need not cost a cent.
+Perhaps this book will interest them all, but the better way is for you
+to read about one constellation and then go out with some of the family
+and find it. This book does not tell about wonderful things you can
+never see; it tells about the wonderful things all of us can see.
+
+I wish you success with your Star Club. Perhaps your uncles and aunts
+will start clubs, too. We have three Star Clubs in our family--one in
+New York, one in Michigan, and one in Colorado. Last winter the
+"Colorado Star Gazers" sent this challenge to the "New Jersey
+Night-Owls:" "_We bet you can't see Venus by daylight!_"
+
+That seemed possible, because during that week the "evening star" was by
+far the brightest object in the sky. But father and daughter searched
+the sky before sunset in vain, and finally we had to ask the "Moonstruck
+Michiganders" how to see Venus while the sun was shining. Back came
+these directions on a postal-card: "Wait until it is dark and any one
+can see Venus. Then find some tree, or other object, which is in line
+with Venus and over which you can just see her. Put a stake where you
+stand. Next day go there half an hour before sunset, and stand a little
+to the west. You will see Venus as big as life. The next afternoon you
+can find her by four o'clock. And if you keep on you will see her day
+before yesterday!"
+
+That was a great "stunt." We did it; and there are dozens like it you
+can do. And that reminds me that father was mistaken about our interest
+lasting only two years. We know that it will not die till we do. For,
+even if we never get a telescope, there will always be new things to
+see. Our club has still to catch Algol, the "demon's eye," which goes
+out and gleams forth every three days, because it is obscured by some
+dark planet we can never see. And we have never yet seen Mira the
+wonderful, which for some mysterious reason dies down to ninth magnitude
+and then blazes up to second magnitude every eleventh month.
+
+Ah, yes, the wonders and the beauties of astronomy ever deepen and
+widen. Better make friends with the stars now. For when you are old
+there are no friends like old friends.
+
+
+
+
+THE DIPPERS AND THE POLE STAR
+
+
+I never heard of any boy or girl who didn't know the Big Dipper. But
+there is one very pleasant thing about the Dipper which children never
+seem to know. With the aid of these seven magnificent stars you can find
+all the other interesting stars and constellations. So true is this that
+a book has been written called "The Stars through a Dipper."
+
+To illustrate, do you know the _Pointers_? I mean the two stars on the
+front side of the Dipper. They point almost directly toward the Pole
+star, or North star, the correct name of which is Polaris. Most children
+can see the Pole star at once because it is the only bright star in that
+part of the heavens.
+
+But if you can't be sure you see the right one, a funny thing happens.
+Your friend will try to show you by pointing, but even if you look
+straight along his arm you can't always be sure. And then, if he tries
+to tell you how far one star is from another, he will try to show you by
+holding his arms apart. But that fails also. And so, we all soon learn
+the easiest and surest way to point out stars and measure distances.
+
+The easiest way to tell any one how to find a star is to get three
+stars in a straight line, or else at right angles.
+
+The surest way to tell any one how far one star is from another is by
+"degrees." You know what degrees are, because every circle is divided
+into 360 of them. And if you will think a moment, you will understand
+why we can see only half the sky at any one time, or 180 degrees,
+because the other half of the sky is on the other side of the earth.
+Therefore, if you draw a straight line from one horizon, clear up to the
+top of the sky and down to the opposite horizon, it is 180 degrees long.
+And, of course, it is only half that distance, or 90 degrees, from
+horizon to zenith. (Horizon is the point where earth and sky seem to
+meet, and zenith is the point straight over your head.)
+
+Now ninety degrees is a mighty big distance in the sky. The Pole star is
+nothing like ninety degrees from the Dipper. It is only twenty-five
+degrees, or about five times the distance between the Pointers. And now
+comes the only thing I will ask you to remember. Look well at the two
+Pointers, because the distance between them, five degrees, is the most
+convenient "foot rule" for the sky that you will ever find. Most of the
+stars you will want to talk about are from two to five times that
+distance from some other star that you and your friends are sure of.
+Perhaps this is a little hard to understand. If so, read it over several
+times, or get some one to explain it to you, for when you grasp it, it
+will unlock almost as many pleasures as a key to the store you like the
+best.
+
+Now, let's try our new-found ruler. Let us see if it will help us find
+the eighth star in the Dipper. That's a famous test of sharp eyes. I
+don't want to spoil your pleasure by telling you too soon where it is.
+Perhaps you would rather see how sharp your eyes are before reading any
+further. But if you can't find the eighth star, I will tell you where to
+look.
+
+Look at the second star in the Dipper, counting from the end of the
+handle. That is a famous star called Mizar. Now look all around Mizar,
+and then, if you can't see a little one near it, try to measure off one
+degree. To do this, look at the Pointers and try to measure off about a
+fifth of the distance between them. Then look about one degree (or less)
+from Mizar, and I am sure you will see the little beauty--its name is
+Alcor, which means "the cavalier" or companion. The two are sometimes
+called "_the horse and rider_"; another name for Alcor is Saidak, which
+means "the test." I shall be very much disappointed if you cannot see
+Saidak, because it is not considered a hard test nowadays for sharp
+eyes.
+
+Aren't these interesting names? Mizar, Alcor, Saidak. They sound so
+Arabian, and remind one of the "Arabian Nights." At first, some of them
+will seem hard, but you will come to love these old names. I dare say
+many of these star names are 4,000 years old. Shepherds and sailors
+were the first astronomers. The sailors had to steer by the stars, and
+the shepherds could lie on the ground and enjoy them without having to
+twist their necks. They saw and named Alcor, thousands of years before
+telescopes were invented, and long before there were any books to help
+them. They saw the demon star, too, which I have never seen. It needs
+patience to see those things; sharp eyes are nothing to be proud of,
+because they are given to us. But patience is something to be eager
+about, because it costs us a lot of trouble to get it.
+
+Let's try for it. We've had a test of sight. Now let's have a test of
+patience. It takes more patience than sharpness of sight to trace the
+outline of the Little Dipper. It has seven stars, too, and the Pole star
+is in the end of the handle. Do you see two rather bright stars about
+twenty-five degrees from the Pole? I hope so, for they are the only
+brightish stars anywhere near Polaris. Well, those two stars are in the
+outer rim of the Little Dipper. Now, I think you can trace it all; but
+to make sure you see the real thing, I will tell you the last secret.
+The handle of the Big Dipper is bent _back_; the handle of the Little
+Dipper is bent _in_.
+
+Now, if you have done all this faithfully, you have worked hard enough,
+and I will reward you with a story. Once upon a time there was a
+princess named Callisto, and the great god Jupiter fell in love with
+her. Naturally, Jupiter's wife, Juno, wasn't pleased, so she changed the
+princess into a bear. But before this happened, Callisto became the
+mother of a little boy named Arcas, who grew up to be a mighty hunter.
+One day he saw a bear and he was going to kill it, not knowing that the
+bear was really his own mother. Luckily Jupiter interfered and saved
+their lives. He changed Arcas into a bear and put both bears into the
+sky. Callisto is the Big Bear, and Arcas is the Little Bear. But Juno
+was angry at that, and so she went to the wife of the Ocean and said,
+"Please, never let these bears come to your home." So the wife of the
+Ocean said, "I will never let them sink beneath the waves." And that is
+why the Big and the Little Dipper never set. They always whirl around
+the Pole star. And that is why you can always see them, though some
+nights you would have to sit up very late.
+
+Is that a true story? No. But, I can tell you a true one that is even
+more wonderful. Once upon a time, before the bear story was invented and
+before people had tin dippers, they used to think of the Little Dipper
+as a little dog. And so they gave a funny name to the Pole star. They
+called it Cynosura, which means "the dog's tail." We sometimes say of a
+great man, "he was the cynosure of all eyes," meaning that everybody
+looked at him. But the original cynosure was and is the Pole star,
+because all the stars in the sky seem to revolve around it. The two
+Dippers chase round it once every twenty-four hours, as you can convince
+yourself some night when you stay up late. So that's all for to-night.
+
+What! You want another true story? Well, just one more. Once upon a time
+the Big Dipper was a perfect cross. That was about 50,000 years ago.
+Fifty thousand years from now the Big Dipper will look like a steamer
+chair. How do I know that? Because, the two stars at opposite ends of
+the Dipper are going in a direction different from the other five stars.
+How do I know that? Why, I don't know it. I just believe it. There are
+lots of things I don't know, and I'm not afraid to say so. I hope you
+will learn how to say "I don't know." It's infinitely better than
+guessing; it saves trouble, and people like you better, because they see
+you are honest. I don't know how the stars in the Big Dipper are moving,
+but the men who look through telescopes and study mathematics say the
+end stars do move in a direction opposite to the others, and they say
+the Dipper _must_ have looked like a cross, and will look like a dipper
+long, long after we are dead. And I believe them.
+
+
+
+
+CONSTELLATIONS YOU CAN ALWAYS SEE
+
+
+There are forty-eight well known constellations, but of these only about
+a dozen are easy to know. I think a dozen is quite enough for children
+to learn. And therefore, I shall tell you how to find only the showiest
+and most interesting.
+
+The best way to begin is to describe the ones that you can see almost
+every night in the year, because you may want to begin any month in the
+year, and you might be discouraged if I talked about things nobody could
+see in that month. There are five constellations you can nearly always
+see, and these are all near the Pole star.
+
+Doubtless you think you know two of them already--the Big and the Little
+Dipper. Ah, I forgot to tell you that these dippers are not the real
+thing. They are merely parts of bigger constellations and their real
+names are Great Bear and Little Bear. The oldest names are the right
+ones. Thousands of years ago, when the Greeks named these groups of
+stars, they thought they looked like two bears. I can't see the
+resemblance.
+
+But for that matter all the figures in the sky are disappointing. The
+people who named the constellations called them lions, and fishes, and
+horses, and hunters, and they thought they could see a dolphin, a
+snake, a dragon, a crow, a crab, a bull, a ram, a swan, and other
+things. But nowadays we cannot see those creatures. We can see the stars
+plainly enough, and they do make groups, but they do not look like
+animals. I was greatly disappointed when I was told this; but I soon got
+over it, because new wonders are always coming on. I think the only
+honest thing to do is to tell you right at the start that you cannot see
+these creatures very well. You will spoil your pleasure unless you take
+these resemblances good-naturedly and with a light heart. And you will
+also spoil your pleasure if you scold the ancients for naming the
+constellations badly. Nobody in the world would change those old names
+now. There is too much pleasure in them. Besides, I doubt if we could do
+much better. I believe those old folks were better observers than we.
+And I believe they had a lighter fancy.
+
+Let us, too, be fanciful for once. I have asked my friend, Mrs. Thomas,
+to draw her notion of some of these famous creatures of the sky. You can
+draw your idea of them too, and it is pleasant to compare drawings with
+friends. There is only one way to see anything like a Great Bear. You
+have to imagine the Dipper upside down and make the handle of the Dipper
+serve for the Bear's tail. What a funny bear to drag a long tail on the
+ground! Miss Martin says he looks more like a chubby hobby-horse. You
+will have to make the bowl of the Dipper into hind legs and use all the
+other stars, somehow, to make a big, clumsy, four-legged animal. And
+what a monster he is! He measures twenty-five degrees from the tip of
+his nose to the root of his tail. Yes, all those miscellaneous faint
+stars you see near the Big Dipper belong to the Great Bear.
+
+[Illustration: Orion fighting the Bull. Above are Orion's two dogs]
+
+[Illustration: The Little Bear, the Queen in her chair, the Twins and
+the Archer]
+
+How the Great Bear looked to the people who named it thousands of years
+ago, we probably shall never know. They left no books or drawings, so
+far as I know. But in every dictionary and book on astronomy you can
+find these bears and other animals drawn so carefully and beautifully
+that it seems as if they _must_ be in the sky, and we must be too dull
+to see them. It is not so. Look at the pictures in this book and, you
+will see that the stars do not outline the animals. Many of them come at
+the wrong places. And so it is with all the costly books and charts and
+planispheres. It is all very interesting, but it isn't true. It's just
+fancy. And when you once understand that it isn't true, you will begin
+to enjoy the fancy. Many a smile you will have, and sometimes a good
+laugh. For instance, the English children call the Dipper "Charles's
+wain" or "the wagon." And the Romans called it "the plough." They
+thought of those seven stars as oxen drawing a plough.
+
+Well, that's enough about the two Bears. I want to tell you about the
+other three constellations you can nearly always see. These are the
+Chair, the Charioteer, and Perseus (pronounced _per'soos_).
+
+The Chair is the easiest to find, because it is like a very bad W, and
+it is always directly opposite the big Dipper, with the Pole star half
+way between the two constellations. There are five stars in the W, and
+to make the W into a Chair you must add a fainter star which helps to
+make the square bottom of the chair. But what a crazy piece of
+furniture! I have seen several ways of drawing it, but none of them
+makes a comfortable chair. I should either fall over backward, or else
+the back of the chair would prod me in the small of my back. The correct
+name of this constellation is Cassiopeia's Chair.
+
+I think this is enough to see and enjoy in one night. To-morrow night
+let us look for the Charioteer.
+
+I love the Charioteer for several reasons. One is that it makes a
+beautiful pentagon, or five-sided figure, with its five brightest stars.
+Another is that it contains the second-brightest star in the northern
+part of the heavens, Capella. The only star in the north that is
+brighter is Vega, but Vega is bluish white or creamy.
+
+If you haven't already found the five-sided figure, I will tell you how
+to find Capella. Suppose you had a gun that would shoot anything as far
+as you wish. Shoot a white string right through the Pointers and hit the
+Pole star. Then place your gun at the Pole star and turn it till it is
+at right angles to that string you shot. Aim away from the big Dipper,
+shoot a bullet forty-five degrees and it will hit Capella.
+
+If that plan doesn't work, try this. Start with the star that is at the
+bottom of the Dipper and nearest the handle. Draw a line half-way
+between the two Pointers and keep on till you come to the first bright
+star. This is Capella, and the distance is about fifty degrees.
+
+Capella means "a kid," or "little goat," and that reminds me of the
+third reason why I enjoy so much the constellation of which Capella is
+the brightest star. In the old times they sometimes called this
+five-sided figure "the goat-carrier." And the shepherds thought they
+could see a man carrying a little goat in his left hand. I am sure you
+can see the kid they meant. It is a triangle of faint stars which you
+see near Capella. That's enough for to-night.
+
+To-morrow night let us look for Perseus. I dare say you know that old
+tale about Perseus rescuing the princess who was chained upon a rock.
+(He cut off the snaky head of Medusa and showed it to the dragon that
+was going to devour the princess, and it turned the monster to stone.
+Remember?) Well, there are constellations named after all the people in
+that story, but although they contain many showy stars, I could never
+make them look like a hero, a princess, a king, and a queen. I do not
+even try to trace out all of Perseus. For I am satisfied to enjoy a very
+beautiful part of it which is called the "Arc of Perseus."
+
+An arc, you know, is a portion of a circle. And the way to find this arc
+is to draw a curve from Capella to Cassiopeia. On nights that are not
+very clear I can see about seven stars in this Arc of Perseus. And the
+reason I love it so much is that it is the most beautiful thing, when
+seen through an opera-glass, that I know. You could never imagine that a
+mere opera-glass would make such a difference. The moment I put it to my
+eyes about a dozen more stars suddenly leap into my sight in and near
+the Arc of Perseus. That's enough. No more stories to-night.
+
+
+
+
+WINTER CONSTELLATIONS
+
+
+By winter constellations I mean those you can see in winter at the
+pleasantest time--the early evening. And I want you to begin with the
+Northern Cross. I hope you can see this before Christmas, for, after
+that, it may be hidden by trees or buildings in the west and you may not
+see it again for a long while. This is because the stars seem to rise in
+the east and set in the west. To prove this, choose some brilliant star
+you can see at five or six o'clock; get it in line with some bush or
+other object over which you can just see it. Put a stake where you
+stand, and then go to the same spot about eight o'clock or just before
+you go to bed. You can tell at once how much the star seems to have
+moved westward.
+
+Another thing, every star rises four minutes later every night, and
+therefore the sky looks a little different at the same hour every
+evening. The stars in the north set for a short time only, but when
+those toward the south set they are gone a long time. For instance, the
+brightest star of all is Sirius, the Dog Star, which really belongs to
+the southern hemisphere. There are only about three months in the year
+when children who go to bed by seven o'clock can see it--January,
+February, and March.
+
+So now you understand why I am so eager that you should not miss the
+pleasure of seeing the famous Northern Cross. But although it is a big
+cross, and easy to find, after you know it, I have never yet known a boy
+who could show it to another boy simply by pointing at it. The surest
+and best way to find it is learn three bright stars first--Altair, Vega,
+and Deneb.
+
+Altair is the brightest star in the Milky Way. It is just at the edge of
+the Milky Way, and you are to look for three stars in a straight line,
+with the middle one brightest. Those three stars make the constellation
+called "the Eagle." The body of the eagle is Altair, and the other two
+stars are the wings. I should say that Altair is about five degrees from
+each of his companions. It is worth half an hour's patient search to
+find the Eagle. Now these three stars in the Eagle point straight toward
+the brightest star in the northern part of the sky--Vega.
+
+To make sure of it, notice four fainter stars near it which make a
+parallelogram--a sort of diamond. These stars are all part of a
+constellation called "the Lyre." If you try to trace out the old musical
+instrument, you will be disappointed; but here is a game worth while.
+Can you see a small triangle made by three stars, of which Vega is one?
+Well, one of those stars is double, and with an opera-glass you can see
+which it is. On very clear nights some people with very sharp eyes can
+see them lying close together, but I never could.
+
+At last we are ready to find the celebrated Northern Cross. First draw a
+line from Altair to Vega. Then draw a line at right angles to this,
+until you come to another bright star--Deneb--which is about as far from
+Vega as Vega is from Altair. Now this beautiful star, Deneb, is the top
+of the Northern Cross. I can't tell you whether the Cross will be right
+or wrong side up when you see it, or on its side. For every
+constellation is likely to change its position during the night, as you
+know from watching the Dipper. But you can tell the Cross by these
+things. There are six stars in it. It is like a kite made of two sticks.
+There are three stars in the crosspiece and four in the long piece.
+Deneb, the brightest star in the cross, is at the top of the long stick.
+
+But you mustn't expect to see a perfect cross. There is one star that is
+a little out of place, and sometimes my fingers fairly "itch to put it
+where it belongs." It is the one that ought to be where the long stick
+of your kite is tacked to the crosspiece. And one of the stars is
+provokingly faint, but you can see it. Counting straight down the long
+piece, it is the third one from Deneb that is faint. It is where it
+ought to be, but I should like to make it brighter. Have you the Cross
+now? If not, have patience. You can't be a "true sport" unless you are
+patient. You can't be a great ball-player, or hunter, or any thing else,
+without resisting, every day, that sudden impulse to "quit the game"
+when you lose. Be a "good loser," smile and try again. That is better
+than to give up, or to win by cheating or sharp practice.
+
+This is the last thing I want you to see in the northern part of the
+sky; and if you have done a good job, let us celebrate by having a
+story.
+
+Once upon a time a cross didn't mean so much to the world as it does
+now. That was before Christ was born. In those old times people did not
+think of the Northern Cross as a cross. They thought of it as a Swan,
+and you can see the Swan if you turn the Cross upside down. Deneb will
+then be in the tail of the Swan, and the two stars which used to be at
+the tips of the crosspiece now become the wings. Is that a true story?
+Yes. If we lived in Arabia the children there could tell us what Deneb
+means. It means "the tail."
+
+Another story? Well, do you see the star in the beak of the Swan, or
+foot of the Cross? What color is it? White? Well, they say this white
+star is really made up of two stars--one yellow and the other blue. That
+is one reason I want to buy a telescope when I can afford it, for even
+the smallest telescope will show that. And Mr. Serviss says that even a
+strong field-glass will help any one see this wonder.
+
+I can't tell you about all the winter constellations in one chapter. We
+have made friends of the northern ones. Now let's see the famous
+southern ones. And let's start a new chapter.
+
+
+
+
+ORION, HIS DOGS, AND THE BULL
+
+
+The most gorgeous constellation in the whole sky is Orion. I really pity
+any one who does not know it, because it has more bright stars in it
+than any other group. Besides, it doesn't take much imagination to see
+this mighty hunter fighting the great Bull. I dare say half the people
+in the United States know Orion and can tell him as quick as they see
+him by the famous "belt of Orion."
+
+This belt is made of three stars, each of which is just one degree from
+the next. That is why the English people call these three stars "the ell
+and yard." Another name for them is "the three kings." You can see the
+"sword of Orion" hanging down from his belt.
+
+As soon as you see these things you will see the four bright stars that
+outline the figure of the great hunter, but only two of them are of the
+first magnitude. The red one has a hard name--Betelgeuse (pronounced
+_bet-el-guz�_). That is a Frenchified word from the Arabic, meaning
+"armpit," because this star marks the right shoulder of Orion. The other
+first-magnitude star is the big white one in the left foot. Its name is
+Rigel (pronounced _re�-jel_) from an Arabian word meaning "the foot."
+
+You can see the giant now, I am sure. Over his left arm hangs a lion's
+skin which he holds out to shield him from the bull's horns. See the
+shield--about four rather faint stars in a pretty good curve? Now look
+for his club which he holds up with his right hand so as to smite the
+bull. See the arm and the club--about seven stars in a rather poor
+curve--beyond the red star Betelgeuse? Now you have him, and isn't he a
+wonder!
+
+It is even easier to see the Bull which is trying to gore Orion. Look
+where Orion is threatening to strike, and you will see a V. How many
+stars in that V? Five. And which is the brightest? That red one at the
+top of the left branch of the V? Yes. That V is the face of the Bull and
+that red star is the baleful eye of the angry Bull which is lowering his
+head and trying to toss Orion. The name of that red eye is Aldebaran
+(pronounced _al-deb�-ar-an_).
+
+I wish Aldebaran meant "red eye," but it doesn't. It is an old Arabian
+word meaning the "hindmost," or the "follower," because every evening it
+comes into view about an hour after you can see the famous group of
+stars called the Pleiades, which are in the shoulder of the Bull.
+
+I do not care to trace the outline of this enormous bull, but his horns
+are a great deal longer than you think at first. If you will extend the
+two arms of that V a long way you will see two stars which may be called
+the tips of his horns. One of these stars really belongs in another
+constellation--our old friend the Charioteer, the one including
+Capella. Wow! what a pair of horns!
+
+But now we come to the daintiest of all constellations--the Seven
+Sisters, or Pleiades (pronounced _plee�-a-deez_).
+
+I can see only six of them, and there is a famous old tale about the
+"lost Pleiad." But I needn't describe them. Every child finds them by
+instinct. Some compare them to a swarm of bees; some to a rosette of
+diamonds; some to dewdrops. But I would not compare them to a dipper as
+some do, because the real Little Dipper is very different. The light
+that seems to drip from the Pleiades is quivering, misty, romantic,
+magical. No wonder many children love the Pleiades best of all the
+constellations. No wonder the poets have praised them for thousands of
+years. The oldest piece of poetry about them that I know of was written
+about 1,500 years before Christ. You can find it in the book of Job. But
+the most poetic description of the Pleiades that I have ever read is in
+Tennyson's poem "Locksley Hall," in which he says they "glitter like a
+swarm of fireflies tangled in a silver braid."
+
+There are a great many old tales about the lost Pleiad. One is that she
+veiled her face because the ancient city of Troy was burned. Another
+story says she ceased to be a goddess when she married a man and became
+mortal. Some people think she was struck by lightning. Others believe
+the big star, Canopus, came by and ran away with her. Still others
+declare she was a new star that appeared suddenly once upon a time, and
+after a while faded away.
+
+For myself, I do not believe any of these stories. One reason why I
+don't is that a seventh star is really there, and many people can really
+see it. Indeed, there are some people so sharp-eyed that on clear nights
+they can see anywhere from eight to eleven. And, what is more, they can
+draw a map or chart showing just where each star seems to them to be.
+
+But the most wonderful stories about the Pleiades are the true stories.
+One is that there are really more than 3,000 stars among the Pleiades.
+Some of them can be seen only with the biggest telescopes. Others are
+revealed only by the spectroscope. And some can be found only by means
+of photography.
+
+But the most amazing thing about the Pleiades is the distances between
+them. They look so close together that you would probably say "the moon
+seems bigger than all of them put together." Sometimes the moon comes
+near the Pleiades, and you expect that the moon will blot them all out.
+But the astronomers say the full moon sails through the Pleiades and
+covers only one of them at a time, as a rule. They even say it is
+possible for the moon to pass through the Pleiades without touching one
+of them! I should like to see that. If anything like it is going to
+occur, the magazine I spoke of in the first chapter will tell me about
+it. And you'd better believe I will stay up to see that, if it takes all
+night!
+
+There are two more constellations in the southern part of the sky that
+ought to be interesting, because they are the two hunting dogs that help
+Orion fight the Bull. But I can't trace these animals, and I don't
+believe it is worth while. The brightest stars in them everybody can see
+and admire--Sirius, the Bigger Dog, and Procyon, the Smaller Dog.
+
+Every one ought to know Sirius, because he is the brightest star of all.
+(Of course, he is not so bright as Venus and Jupiter, but they are
+planets.) To find him, draw a line from the eye of the Bull through the
+belt of Orion and extend it toward the southeast about twenty degrees.
+They call him the Dog star because he follows the heels of Orion. And
+people still call the hottest days of summer "dog days" because 400
+years before Christ the Romans noticed that the Dog star rose just
+before the sun at that time. The Romans thought he chased the sun across
+the sky all day and therefore was responsible for the great heat. But
+that was a foolish explanation. And so is the old notion that dogs are
+likely to go mad during the dog days "because the dog star is in the
+ascendant." So is the idea that Sirius is an unlucky star.
+
+There are no lucky or unlucky stars. These are all superstitions, and we
+ought to be ashamed to believe any superstition. Yet for thousands of
+years before we had public schools and learned to know better, people
+believed that every one was born under a lucky star or an unlucky one,
+and they believe that farmers ought to plant or not plant, according to
+the size of the moon. Now we know that is all bosh. Those old
+superstitions have done more harm than good. One of the most harmful was
+the belief in witches. Let us resolve never to be afraid of these old
+tales, but laugh at them.
+
+Why should anybody be afraid of anything so lovely as Sirius? I used to
+think Sirius twinkled more than any other star. But that was bad
+reasoning on my part. I might have noticed that every star twinkles more
+near the horizon than toward the zenith. I might have noticed that stars
+twinkle more on clear, frosty nights than when there is a little uniform
+haze. And putting those two facts together I might have reasoned that
+the stars never really twinkle at all; they only seem to. I might have
+concluded that the twinkling is all due to the atmosphere--that blanket
+of air which wraps the earth around. The nearer the earth, the thicker
+the air, and the more it interferes with the light that comes to us from
+the stars.
+
+They say that Sirius never looks exactly alike on two successive nights.
+"It has a hundred moods," says Mr. Serviss, "according to the state of
+the atmosphere. By turns it flames, it sparkles, it glows, it blazes, it
+flares, it flashes, it contracts to a point, and sometimes when the air
+is still, it burns with a steady white light." (Quotation somewhat
+altered and condensed.)
+
+It is a pity that so fine a star as Procyon should be called the
+"Smaller Dog," because it suffers unjustly by comparison with Sirius. If
+it were in some other part of the sky we might appreciate it more,
+because it is brighter than most of the fifteen first-magnitude stars we
+can see. My brother William has grown to love it, but perhaps that is
+because he always "sympathizes with the under dog." He was the youngest
+brother and knows. And curiously enough he was nicknamed "the dog"--just
+why, I don't know.
+
+To find Procyon, drawn a line from Sirius northeast about twenty
+degrees. And to make sure, draw one east from Betelgeuse about the same
+distance. These three stars make a triangle of which the sides are
+almost equal.
+
+The name Procyon means "before the dog" referring to the fact that you
+can see him fifteen or twenty minutes earlier every night than you can
+see Sirius.
+
+The only kind word about Procyon I have heard in recent years was in
+connection with that miserable business of Dr. Cook and the North Pole.
+A Captain Somebody-or-other was making observations for Dr. Cook, and he
+wanted to know what time it was. He had no watch and didn't want to
+disturb any one. So he looked out of the window and saw by the star
+Procyon that it was eleven o'clock.
+
+That sounds mysterious, but it is easy if you have a planisphere like
+ours. Last winter when we were all enjoying Orion, the Bull, and the two
+Dogs, I used to whirl the planisphere around to see where they would be
+at six o'clock at night, at eight, at ten, at midnight, and even at six
+o'clock in the morning. And so, if I waked up in the night I could tell
+what time it was without even turning my head. Sometimes I looked out of
+my window, saw Orion nearly overhead and knew it must be midnight. And
+sometimes I woke up just before daybreak and saw the great Bull backing
+down out of sight in the west, the mighty Hunter still brandishing his
+club, and his faithful Dogs following at his heels.
+
+
+
+
+SEVEN FAMOUS CONSTELLATIONS
+
+
+There are only seven more constellations that seem to me interesting
+enough for every one to know and love all his life. These are:
+
+  The Lion (Spring)
+
+  The Twins (Spring)
+
+  The Virgin (Summer)
+
+  The Herdsman (Summer)
+
+  The Northern Crown (Summer)
+
+  The Scorpion (Summer)
+
+  Southern Fish (Autumn)
+
+I have named the seasons when, according to some people, these
+constellations are most enjoyable. But these are not the only times when
+you can see them. (If you had that seventy-five-cent planisphere, now,
+you could always tell which constellations are visible and just where to
+find them.) No matter what time of year you read this chapter, it is
+worth while to go out and look for these marvels. You can't possibly
+miss them all.
+
+Have you ever seen a Sickle in the sky? It's a beauty, and whenever I
+have seen it it has been turned very conveniently for me, because I am
+left-handed. It is so easy to find that I am almost ashamed to tell. But
+if you need help, draw a line through the Pointers backward, away from
+the Pole star, about forty degrees, and it will come a little west of
+the Sickle. The Sickle is only part of the Lion--the head and the
+forequarters. Only fanciful map-makers can trace the rest of the Lion.
+The bright star at the end of the handle is Regulus, which means "king,"
+from the stupid old notion that this star ruled the lives of men. To
+this day people speak of the "Royal Star," meaning Regulus. And at the
+end of this chapter I will tell you about three other stars which the
+Persians called "royal stars."
+
+Another constellation which children particularly love is the
+Twins--Castor and Pollux. But the sailors got there first! For thousands
+of years the twins have been supposed to bring good luck to sailors. I
+don't believe a word of it. But I do know that sailors gloat over Castor
+and Pollux, and like them better than any other stars. The whole
+constellation includes all the stars east of the Bull and between the
+Charioteer and Procyon. But another way to outline the twins is to look
+northeast of Orion where you will see two rows of stars that run nearly
+parallel. To me the brothers seem to be standing, but all the old
+picture-makers show them sitting with their arms around each other, the
+two brightest stars being their eyes. The eyes are about five degrees
+apart--the same as the Pointers.
+
+Pollux is now brighter than Castor, but for thousands of years it was
+just the other way. It is only within three hundred years that this
+change has taken place. Whether Castor has faded or Pollux brightened,
+or both, I do not know. Anyhow, Castor is not quite bright enough to be
+a first magnitude star. Three hundred years is a short time in the
+history of man, and only a speck in the history of the stars. Three
+hundred years ago they killed people in Europe just because of the
+church they went to. That was why the Pilgrim Fathers sailed from
+England in 1620, and made the first permanent settlement in America,
+except, of course, Jamestown, Va., in 1607.
+
+There are plenty of stories about old Castor and Pollux, and, like all
+the other myths, they conflict, more or less. But all agree that these
+two brothers went with Jason in the ship Argo, shared his adventures and
+helped him get the golden fleece. And all agree that Castor and Pollux
+were "born fighters." And that is why the Roman soldiers looked up to
+these stars and prayed to them to help them win their battles.
+
+Now for the four summer constellations every one ought to know. The
+first thing to look for is two famous red or reddish stars--Arcturus and
+Antares.
+
+The way you find Arcturus is amusing. Look for the Big Dipper and find
+the star at the bottom of the dipper nearest the handle. Got it? Now
+draw a curve that will connect it with all the stars in the handle, and
+when you come to the end of the handle keep on till you come to the
+first very bright star--about twenty-five degrees. That is the monstrous
+star Arcturus, probably the biggest and swiftest star we can ever see
+with the naked eye in the northern hemisphere. He is several times as
+big as our sun, and his diameter is supposed to be several million
+miles. He is called a "runaway sun," because he is rushing through space
+at the rate of between two hundred and three hundred miles a second.
+That means between seventeen and thirty-four million miles a day!
+
+He is coming toward us, too! At such a rate you might think that
+Arcturus would have smashed the earth to pieces long ago. But he is
+still very far away, and there is no danger. Some people say that if Job
+were to come to life, the sky would seem just the same to him as it did
+3,400 years ago. The only difference he might notice would be in
+Arcturus. That would seem to him out of place by a distance about three
+times the apparent diameter of the moon.
+
+Some people believe this because Job said, "Canst thou guide Arcturus
+with his sons?" and therefore they imagine that he meant this red star.
+But I believe he meant the Big Dipper. For in King James's time, when
+the Bible was translated into English, the word "Arcturus" meant the Big
+Dipper or rather the Great Bear. And for centuries before it meant the
+Great Bear. One proof of it is that "Arcturus" comes from an old Greek
+word meaning "bear"--the same word from which we get arctic. It is only
+within a few hundred years that astronomers have agreed to call the
+Great Bear "Ursa Major," and this red star Arcturus. So I think all the
+books which say Job mentioned this red star are mistaken. I believe
+Webster's Dictionary is correct in this matter, and I believe the
+Revised Version translates Job's Hebrew phrase more correctly when it
+says, "Canst thou guide the Bear with her train?"
+
+Anyhow, Arcturus is a splendid star--the brightest in the constellation
+called the "Herdsman" or Bo�tes. It is not worth while to trace the
+Herdsman, but here is an interesting question. Is Arcturus really red?
+The books mostly say he is yellow. They say he looks red when he is low
+in the sky, and yellow when he is high. How does he look to you? More
+yellow than red?
+
+Well, there's no doubt about Antares being red. To find him, draw a long
+line from Regulus through Arcturus to Antares, Arcturus being more than
+half way between the other two. But if Regulus and the Sickle are not
+visible, draw a line from Altair, at right angles to the Eagle, until
+you come to a bright star about sixty degrees away. You can't miss
+Antares, for he is the only red star in that part of the sky.
+
+Antares belongs to a showy constellation called the Scorpion. I cannot
+trace all the outline of a spider-like creature, but his poisonous tail
+or "stinger" is made by a curved line of stars south and east of
+Antares. And you can make a pretty fan by joining Antares to several
+stars in a curve which are west of Antares and a little north. There is
+an old tale that this Scorpion is the one that stung Orion to death when
+he began to "show off" and boast that there was no animal in the world
+that could kill him.
+
+Another very bright star in the southern part of the sky is Spica. To
+find it, start with the handle of the Dipper, and making the same
+backward curve which helped you to find Arcturus, keep on till you come
+to the white star Spica--say thirty degrees beyond Arcturus. This is the
+brightest star in the constellation called "the Virgin." It is not worth
+while trying to trace her among nearly forty faint stars in this
+neighbourhood. But she is supposed to be a winged goddess who holds up
+in her right hand an _ear of wheat_, and that is what Spica means.
+
+Now for an autumn constellation--the Southern Fish. I don't care if you
+fail to outline a fish, but I do want you to see the bright star that is
+supposed to be in the fish's mouth. And I don't want you to balk at its
+hard name--Fomalhaut (pronounced _fo�-mal-o_). It is worth a lot of
+trouble to know it as a friend. To find it, you have to draw an
+exceedingly long line two-thirds of the way across the whole sky. Start
+with the Pointers. Draw a line through them and the Pole star and keep
+clear on until you come to a solitary bright star rather low down in the
+south. That is Fomalhaut. It looks lonely and is lonely, even when you
+look at it through a telescope.
+
+And now for the last story. Once upon a time the Persians thought there
+must be four stars that rule the lives of men. So they picked out one in
+the north and one in the south and one in the east and one in the west,
+just as if they were looking for four bright stars to mark the points of
+the compass. If you want to find them yourself without my help don't
+read the next sentence, but shut this book and go out and see. Then
+write down on a piece of paper the stars you have selected and compare
+them with the list I am about to give. Here are the four royal stars of
+the Persians: Fomalhaut for the north, Regulus for the south, Aldebaran
+for the east, and Antares for the west.
+
+Why doesn't this list agree with yours? Because Persia is so far south
+of where we live. Ah, there are very few things that are absolutely
+true. Let's remember that and not be too sure: for everything depends
+upon the point of view! I hope you will see Fomalhaut before Christmas,
+before he disappears in the west. He is with us only five months and is
+always low--near the horizon. But the other seven months in the year he
+gladdens the children of South America and the rest of the southern
+hemisphere, for they see him sweeping high and lonely far up into their
+sky and down again.
+
+But the loveliest of all the constellations described in this chapter is
+the Northern Crown. It is not a perfect crown--only about half a
+circle--but enough to suggest a complete ring. Look for it east of
+Arcturus. I can see seven or eight stars in the half-circle, one of
+which is brighter than all the others. That one is called "the Pearl."
+The whole constellation is only fifteen degrees long, but "fine things
+come in small packages"; and children grow to love the Northern Crown
+almost as much as they love the Pleiades.
+
+
+
+
+THE TWENTY BRIGHTEST STARS
+
+
+If you have seen everything I have described so far, you have reason to
+be happy. For now you know sixteen of the most famous constellations and
+fifteen of the twenty brightest stars. There are only twenty stars of
+the first magnitude. "Magnitude" ought to mean size, but it doesn't. It
+means brightness--or rather the apparent brightness--of the stars when
+seen by us. The word magnitude was used in the old days before
+telescopes, when people thought the brighter a star is the bigger it
+must be. Now we know that the nearer a star is to us the brighter it is,
+and the farther away the fainter. Some of the bright stars are
+comparatively near us, some are very far. Deneb and Canopus are so far
+away that it takes over three hundred years for their light to reach us.
+What whoppers they must be--many times as big as our sun.
+
+Here is a full list of the twenty stars of the first magnitude arranged
+in the order of their brightness. You will find this table very useful.
+
+ ----------------+---------------+-------------+--------------------------
+  Stars          | Pronounced    |Constellation|   Interesting facts
+ ----------------+---------------+-------------+--------------------------
+ Sirius          | _sir�i-us_    | Big Dog     | Brightest star. Nearest
+                 |               |             | star visible in Northern
+                 |               |             | hemisphere
+ Canopus*        | _ca-no�pus_   | Ship Argo   | Perhaps the largest body
+                 |               |             | in universe
+ Alpha Centauri* | _al�fa        |             |
+                 |  sen-taw�re_  | Centaur     | Nearest star. Light four
+                 |               |             | years away
+ Vega            | _ve�ga_       | Lyre        | Brightest star in the
+                 |               |             | Northern sky. Bluish
+ Capella         | _ca-pell�a_   | Charioteer  | Rivals Vega, but opposite
+                 |               |             | the pole. Yellowish
+ Arcturus        | _ark-tu�rus_  | Herdsman    | Swiftest of the bright
+                 |               |             | stars. 200 miles a second
+ Rigel           | _re�jel_      | Orion       | Brightest star in Orion.
+                 |               |             | White star in left foot
+ Procyon         | _pro�si-on_   | Little Dog  | Before the dog. Rises a
+                 |               |             | little before Sirius
+ Achernar*       | _a-ker�nar_   | River Po    | Means the end of the river
+ Beta Centauri*  | _ba�ta        |             |
+                 |  sen-taw�re_  | Centaur     | This and its mate point to
+                 |               |             | the Southern Cross
+ Altair          | _al-tare�_    | Eagle       | Helps you find Vega and
+                 |               |             | Northern Cross
+ Betelgeuse      | _bet-el-guz�_ | Orion       | Means "armpit." The red
+                 |               |             | star in the right shoulder
+ Alpha Crucis*   | _al�fa        | Southern    |
+                 |  cru�sis_     |  Cross      | At the base of the most
+                 |               |             | famous Southern
+                 |               |             | constellation
+ Aldebaran       | _al-deb�a-ran_| Bull        | The red eye in the V
+ Pollux          | _pol�lux_     | Twins       | Brighter than Castor
+ Spica           | _spi�ca_      | Virgin      | Means ear of wheat
+ Antares         | _an-ta�rez_   | Scorpion    | Red star. Name means
+                 |               |             | "looks like Mars"
+ Fomalhaut       | _fo�mal-o_    | Southern    |
+                 |               |  Fish       | The lonely star in the
+                 |               |             | Southern sky
+ Deneb           | _den�eb_      | Swan        | Top of Northern Cross,
+                 |               |             | or tail of Swan
+ Regulus         | _reg�u-lus_   | Lion        | The end of the handle
+                 |               |             | of the Sickle
+ ----------------+---------------+-------------+--------------------------
+
+The five stars marked * belong to the Southern hemisphere, and we can
+never see them unless we travel far south. Last winter I went to Florida
+and saw Canopus, but to see the Southern Cross you should cross the
+Tropic of Cancer.
+
+
+
+
+HOW TO LEARN MORE
+
+
+All I can hope to do in this book is to get you enthusiastic about
+astronomy. I don't mean "gushy." Look in the dictionary and you will
+find that the enthusiast is not the faddist. He is the one who sticks to
+a subject for a lifetime.
+
+Nor do I care a rap whether you become an astronomer--or even buy a
+telescope. There will be always astronomers coming on, but there are too
+few people who know and love even a few of the stars. I want you to make
+popular astronomy a life-long hobby. Perhaps you may have to drop it for
+ten or fifteen years. Never mind, you will take up the study again. I
+can't expect you to read a book on stars if you are fighting to make a
+living or support a family, unless it really rests you to read about the
+stars. It does rest me. When things go wrong at the office or at home, I
+can generally find rest and comfort from music. And if the sky is clear,
+I can look at the stars, and my cares suddenly seem small and drop away.
+
+Let me tell you why and how you can get the very best the stars have to
+teach you, without mathematics or telescope. Follow this programme and
+you need never be afraid of hard work, or of exhausting the pleasures
+of the subject. Go to your public library and get one of the books I
+recommend in this chapter, and read whatever interests you. I don't care
+whether you take up planets before comets or comets before planets, but
+whatever you do do it well. Soak the interesting facts right in. Nail
+them down. See everything the book talks about. Make notes of things to
+watch for. Get a little blank book and write down the date you first saw
+each thing of interest. Write down the names of the constellations you
+love most. Before you lay down any star book you are reading, jot down
+the most wonderful and inspiring thing you have read--even if you have
+only time to write a single word that may recall it all to you. Treasure
+that little note book as long as you live. Every year it will get more
+precious to you.
+
+Now for the books:
+
+1. _Martin._ _The Friendly Stars._ Harper & Brothers, New York, 1907.
+
+This book teaches you first the twenty brightest stars and then the
+constellations. I cannot say that this, or any other, is the "best
+book," but it has helped me most, and I suppose it is only natural that
+we should love best the first book that introduces us to a delightful
+subject.
+
+2. _Serviss._ _Astronomy with the Naked Eye._ Harper & Brothers, New
+York, 1908.
+
+This teaches you the constellations first and the brightest stars
+incidentally. Also it gives the old myths.
+
+3. _Serviss._ _Astronomy with an Opera-Glass._ D. Appleton & Co., New
+York, 1906.
+
+4. _Serviss._ _Pleasures of the Telescope._ D. Appleton & Co., New York,
+1905.
+
+5. _Milham._ _How to Identify the Stars._ The Macmillan Co., New York,
+1909.
+
+This gives a list of eighty-eight constellations, including thirty-six
+southern ones, and has tracings of twenty-eight.
+
+6. _Elson._ _Star Gazer's Handbook._ Sturgis & Walton Co., New York,
+1909.
+
+About the briefest and cheapest. Has good charts and makes a specialty
+of the myths.
+
+7. _Serviss._ _Curiosities of the Sky._ Harper & Brothers, New York.
+
+Tells about comets, asteroids, shooting stars, life on Mars, nebul�,
+temporary stars, coal-sacks, Milky Way, and other wonders.
+
+8. _Ball._ _Starland._ Ginn & Co., Boston, New York, etc., 1899.
+
+This tells about a great many interesting experiments in astronomy that
+children can make.
+
+       *       *       *       *       *
+
+If I had only a dollar or less to spend on astronomy I should buy a
+planisphere. I got mine from Thomas Whittaker, No. 2 Bible House, New
+York. It cost seventy-five cents, and will tell you where to find any
+star at any time in the year. It does not show the planets, however. A
+planisphere that will show the planets costs about five dollars.
+However, there are only two very showy planets, viz., Venus and Jupiter.
+Any almanac will tell you (for nothing) when each of these is morning
+star, and when each of them is evening star.
+
+The best newspaper about stars, as far as I know, is a magazine called
+_The Monthly Evening Sky Map_, published by Leon Barritt, 150 Nassau
+St., New York. It costs a dollar a year. It gives a chart every month,
+showing all the planets, and all the constellations. Also it tells you
+about the interesting things, like comets, before they come.
+
+Good-bye. I hope you will never cease to learn about and love the earth
+and the sky. Perhaps you think you have learned a great deal already.
+But your pleasures have only begun. Wait till you learn about how the
+world began, the sun and all his planets, the distances between the
+stars, and the millions of blazing suns amid the Milky Way!
+
+
+THE END
+
+[Illustration: THE SKY IN WINTER]
+
+NOTE.--These simplified star maps are not as accurate as a planisphere,
+but they may be easier for children. All star maps are like ordinary
+maps, except that east and west are transposed. The reason for this is
+that you can hold a star map over your head, with the pole star toward
+the north, and the map will then match the sky. These maps contain some
+constellations that are only for grown-ups to study. The Winter
+constellations every child should know are:
+
+  AURIGA, the Charioteer
+  CANIS MAJOR, the Big Dog
+  CANIS MINOR, the Little Dog
+  CASSIOPEIA, the Queen in Her Chair
+  CYGNUS, the Swan
+  LEO, the Lion
+  ORION, the Hunter
+  PERSEUS, Which Has the Arc
+  TAURUS, the Bull
+  URSA MAJOR, the Great Bear
+  URSA MINOR, the Little Bear
+
+[Illustration: THE SKY IN SPRING]
+
+NOTE.--Once upon a time all the educated people spoke Latin. It was the
+nearest approach to a universal language. So most of the constellations
+have Latin names. The English, French and German names are all
+different, but if all children would learn the Latin names they could
+understand one another. The Spring constellations every child should
+know are:
+
+  LEO, the Lion
+  LYRA, the Lyre
+  CASSIOPEIA, the Queen in her Chair
+  SCORPIO, the Scorpion
+  URSA MAJOR, the Great Bear
+  URSA MINOR, the Little Bear
+  VIRGO, the Virgin
+
+[Illustration: THE SKY IN SUMMER]
+
+NOTE.--Every sky map is good for three months, in this way: If this is
+correct on June 1st at 10 P.M., it will be correct July 1st at 8 P.M.,
+and August 1st at 6 P.M. This is because the stars rise four minutes
+earlier every night. Thus, after thirty days, any star will rise thirty
+times four minutes earlier, or 120 minutes, or two hours. Children need
+not learn all the Summer constellations. The most interesting are:
+
+  AURIGA, the Charioteer
+  CANIS MAJOR, the Big Dog
+  CYGNUS, the Swan
+  LYRA, the Lyre
+  SCORPIO, the Scorpion
+
+[Illustration: THE SKY IN AUTUMN]
+
+NOTE.--This book tells how to find all the most interesting stars and
+constellations without maps, but many people prefer them. How to use
+star maps is explained under "The Sky in Winter." The Autumn
+constellations most interesting to children are:
+
+  AQUILA, the Eagle
+  AURIGA, the Charioteer
+  CASSIOPEIA, the Queen in Her Chair
+  CYGNUS, the Swan
+  LYRA, the Lyre
+  PERSEUS, Which Has the Arc
+  TAURUS, the Bull
+  URSA MAJOR, the Great Bear
+  URSA MINOR, the Little Bear
+
+
+Transcriber's notes
+
+  Page 124 "streams, runing" corrected to "streams, running"
+  Page 127 "where he globe" corrected to "where the globe"
+  Page 138 "ceatures to prove" corrected to "creatures to prove"
+  Page 216 "this consellation is" corrected to "this constellation is"
+  Page 203 "Everybirth day" corrected to "Every birthday"
+
+
+
+
+
+
+
+End of the Project Gutenberg EBook of Earth and Sky Every Child Should Know, by 
+Julia Ellen Rogers
+
+*** END OF THIS PROJECT GUTENBERG EBOOK EARTH AND SKY ***
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+  <head>
+    <meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1" />
+    <title>
+      The Project Gutenberg eBook of Earth And Sky Every Child Should Know, by Julia Ellen Rogers.
+    </title>
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+
+<pre>
+
+The Project Gutenberg EBook of Earth and Sky Every Child Should Know, by 
+Julia Ellen Rogers
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Earth and Sky Every Child Should Know
+       Easy studies of the earth and the stars for any time and place
+
+Author: Julia Ellen Rogers
+
+Release Date: May 30, 2010 [EBook #32598]
+
+Language: English
+
+Character set encoding: ISO-8859-1
+
+*** START OF THIS PROJECT GUTENBERG EBOOK EARTH AND SKY ***
+
+
+
+
+Produced by Juliet Sutherland, Christine D. and the Online
+Distributed Proofreading Team at http://www.pgdp.net
+
+
+
+
+
+
+</pre>
+
+
+<div class="figcenter" style="width: 322px;">
+<img src="images/cover_th.jpg" width="322" height="500" alt="" title="" />
+</div>
+<p><a name="frontis" id="frontis"></a></p>
+<div class="figcenter" style="width: 377px;">
+<img src="images/frontis_th.jpg" width="377" height="500" alt="Pike&#39;s Peak, Colorado" title="" />
+<span class="caption">Pike&#39;s Peak, Colorado</span>
+</div>
+
+<div class='padding'>
+<h1>
+EARTH <small>AND</small> SKY EVERY<br />
+CHILD SHOULD KNOW<br />
+</h1>
+
+<p class='center'>
+EASY STUDIES OF THE EARTH AND THE<br />
+STARS FOR ANY TIME AND PLACE<br />
+</p>
+
+<h3>BY</h3>
+
+<h2>JULIA ELLEN ROGERS</h2>
+
+<p class='center'>
+AUTHOR OF<br />
+"THE TREE BOOK," "THE SHELL BOOK," "KEY TO THE NATURE<br />
+LIBRARY," "TREES EVERY CHILD SHOULD KNOW."<br />
+</p></div>
+<div class='padding'>
+<p class='center'>
+ILLUSTRATED BY<br />
+THIRTY-ONE PAGES OF PHOTOGRAPHS AND DRAWINGS<br />
+</p>
+
+<div class="figcenter" style="width: 100px;">
+<img src="images/crest.jpg" width="100" height="98" alt="" title="" />
+</div></div>
+<div class='padding'>
+<p class='center'>
+NEW YORK<br />
+GROSSET &amp; DUNLAP<br />
+PUBLISHERS<br />
+</p></div>
+<hr style="width: 65%;" />
+
+<p class='center'>
+COPYRIGHT, 1910, BY DOUBLEDAY, PAGE &amp; COMPANY<br />
+PUBLISHED, OCTOBER, 1910<br />
+<br />
+ALL RIGHTS RESERVED, INCLUDING THAT OF TRANSLATION<br />
+INTO FOREIGN LANGUAGES, INCLUDING THE SCANDINAVIAN<br />
+</p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="ACKNOWLEDGMENTS" id="ACKNOWLEDGMENTS"></a>ACKNOWLEDGMENTS</h2>
+
+
+<p>A number of the photographs in this volume are used by permission of the
+American Museum of Natural History. The star maps and drawings of the
+constellations are by Mrs. Jerome B. Thomas. The poem by Longfellow,
+quoted in part, is with the permission of the publishers, Houghton,
+Mifflin &amp; Co.</p>
+
+<p><span class='pagenum'><a name="Page_vii" id="Page_vii">[Pg vii]</a></span></p>
+
+<hr style="width: 65%;" />
+<h2><a name="CONTENTS" id="CONTENTS"></a>CONTENTS</h2>
+
+
+<p><span class='pagenum'><a name="Page_viii" id="Page_viii">[Pg viii]</a></span></p>
+<div class='center'>
+<table border="0" cellpadding="4" cellspacing="0" summary="">
+<tr><td align='center' colspan='2'><i>PART I. THE EARTH</i></td></tr>
+<tr><td align='left'></td><td align='right'>PAGE</td></tr>
+<tr><td align='left'><span class="smcap">The Great Stone Book</span></td><td align='right'><a href="#Page_3">3</a></td></tr>
+<tr><td align='left'><span class="smcap">The Fossil Fish</span></td><td align='right'><a href="#Page_6">6</a></td></tr>
+<tr><td align='left'><span class="smcap">The Crust of the Earth</span></td><td align='right'><a href="#Page_9">9</a></td></tr>
+<tr><td align='left'><span class="smcap">What Is the Earth Made of?</span></td><td align='right'><a href="#Page_14">14</a></td></tr>
+<tr><td align='left'><span class="smcap">The First Dry Land</span></td><td align='right'><a href="#Page_22">22</a></td></tr>
+<tr><td align='left'><span class="smcap">A Study of Granite</span></td><td align='right'><a href="#Page_27">27</a></td></tr>
+<tr><td align='left'><span class="smcap">Metamorphic Rocks</span></td><td align='right'><a href="#Page_31">31</a></td></tr>
+<tr><td align='left'><span class="smcap">The Air in Motion</span></td><td align='right'><a href="#Page_35">35</a></td></tr>
+<tr><td align='left'><span class="smcap">The Work of the Wind</span></td><td align='right'><a href="#Page_44">44</a></td></tr>
+<tr><td align='left'><span class="smcap">Rain in Summer</span>, <i>by Henry W. Longfellow</i></td><td align='right'><a href="#Page_50">50</a></td></tr>
+<tr><td align='left'><span class="smcap">What Becomes of the Rain?</span></td><td align='right'><a href="#Page_51">51</a></td></tr>
+<tr><td align='left'><span class="smcap">The Soil in Fields and Gardens</span></td><td align='right'><a href="#Page_58">58</a></td></tr>
+<tr><td align='left'><span class="smcap">The Work of Earthworms</span></td><td align='right'><a href="#Page_63">63</a></td></tr>
+<tr><td align='left'><span class="smcap">Quiet Forces That Destroy Rocks</span></td><td align='right'><a href="#Page_68">68</a></td></tr>
+<tr><td align='left'><span class="smcap">How Rocks Are Made</span></td><td align='right'><a href="#Page_72">72</a></td></tr>
+<tr><td align='left'><span class="smcap">Getting Acquainted With a River</span></td><td align='right'><a href="#Page_78">78</a></td></tr>
+<tr><td align='left'><span class="smcap">The Ways of Rivers</span></td><td align='right'><a href="#Page_84">84</a></td></tr>
+<tr><td align='left'><span class="smcap">The Story of a Pond</span></td><td align='right'><a href="#Page_90">90</a></td></tr>
+<tr><td align='left'><span class="smcap">The Riddle of the Lost Rocks</span></td><td align='right'><a href="#Page_93">93</a></td></tr>
+<tr><td align='left'><span class="smcap">The Question Answered</span></td><td align='right'><a href="#Page_96">96</a></td></tr>
+<tr><td align='left'><span class="smcap">Glaciers Among the Alps</span></td><td align='right'><a href="#Page_98">98</a></td></tr>
+<tr><td align='left'><span class="smcap">The Great Ice Sheet</span></td><td align='right'><a href="#Page_104">104</a></td></tr>
+<tr><td align='left'><span class="smcap">Following Some Lost Rivers</span></td><td align='right'><a href="#Page_110">110</a></td></tr>
+<tr><td align='left'><span class="smcap">The Mammoth Cave of Kentucky</span></td><td align='right'><a href="#Page_114">114</a></td></tr>
+<tr><td align='left'><span class="smcap">Land Building by Rivers</span></td><td align='right'><a href="#Page_121">121</a></td></tr>
+<tr><td align='left'><span class="smcap">The Making of Mountains</span></td><td align='right'><a href="#Page_126">126</a></td></tr>
+<tr><td align='left'><span class="smcap">The Lava Flood of the Northwest</span></td><td align='right'><a href="#Page_130">130</a></td></tr>
+<tr><td align='left'><span class="smcap">The First Living Things</span></td><td align='right'><a href="#Page_134">134</a></td></tr>
+<tr><td align='left'><span class="smcap">An Ancient Beach at Ebb Tide</span></td><td align='right'><a href="#Page_138">138</a></td></tr>
+<tr><td align='left'><span class="smcap">The Lime Rocks</span></td><td align='right'><a href="#Page_147">147</a></td></tr>
+<tr><td align='left'><span class="smcap">The Age of Fishes</span></td><td align='right'><a href="#Page_152">152</a></td></tr>
+<tr><td align='left'><span class="smcap">King Coal</span></td><td align='right'><a href="#Page_155">155</a></td></tr>
+<tr><td align='left'><span class="smcap">How Coal Was Made</span></td><td align='right'><a href="#Page_160">160</a></td></tr>
+<tr><td align='left'><span class="smcap">The Most Useful Metal</span></td><td align='right'><a href="#Page_167">167</a></td></tr>
+<tr><td align='left'><span class="smcap">The Age of Reptiles</span></td><td align='right'><a href="#Page_175">175</a></td></tr>
+<tr><td align='left'><span class="smcap">The Age of Mammals</span></td><td align='right'><a href="#Page_180">180</a></td></tr>
+<tr><td align='left'><span class="smcap">The Horse and His Ancestors</span></td><td align='right'><a href="#Page_186">186</a></td></tr>
+<tr><td align='left'><span class="smcap">The Age of Man</span></td><td align='right'><a href="#Page_194">194</a></td></tr>
+<tr><td align='center' colspan='2'><i>PART II. THE SKY</i></td></tr>
+<tr><td align='left'><span class="smcap">Every Family a "Star Club"</span></td><td align='right'><a href="#Page_201">201</a></td></tr>
+<tr><td align='left'><span class="smcap">The Dippers and the Pole Star</span></td><td align='right'><a href="#Page_207">207</a></td></tr>
+<tr><td align='left'><span class="smcap">Constellations You Can Always See</span></td><td align='right'><a href="#Page_213">213</a></td></tr>
+<tr><td align='left'><span class="smcap">Winter Constellations</span></td><td align='right'><a href="#Page_219">219</a></td></tr>
+<tr><td align='left'><span class="smcap">Orion, His Dogs, and the Bull</span></td><td align='right'><a href="#Page_223">223</a></td></tr>
+<tr><td align='left'><span class="smcap">Seven Famous Constellations</span></td><td align='right'><a href="#Page_231">231</a></td></tr>
+<tr><td align='left'><span class="smcap">The Twenty Brightest Stars</span></td><td align='right'><a href="#Page_239">239</a></td></tr>
+<tr><td align='left'><span class="smcap">How to Learn More</span></td><td align='right'><a href="#Page_241">241</a></td></tr>
+</table></div><p><span class='pagenum'><a name="Page_ix" id="Page_ix">[Pg ix]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="ILLUSTRATIONS" id="ILLUSTRATIONS"></a>ILLUSTRATIONS</h2>
+
+
+<p><span class='pagenum'><a name="Page_x" id="Page_x">[Pg x]</a></span></p>
+<div class='center'>
+<table border="0" cellpadding="4" cellspacing="0" summary="">
+<tr><td align='left'>Pike's Peak</td><td align='left'><i><a href="#frontis">Frontispiece</a></i></td></tr>
+<tr><td align='left'></td><td align='left'>FACING PAGE</td></tr>
+<tr><td align='left'>Sand Dunes in Arizona</td><td align='right'><a href="#Page_44">44</a></td></tr>
+<tr><td align='left'>Grand Ca&ntilde;on of the Colorado</td><td align='right'><a href="#Page_45">45</a></td></tr>
+<tr><td align='left'>Castles Carved by Rain and Wind</td><td align='right'><a href="#Page_52">52</a></td></tr>
+<tr><td align='left'>Where All the Water Comes From</td><td align='right'><a href="#Page_53">53</a></td></tr>
+<tr><td align='left'>The Richest Gold and Silver Mines</td><td align='right'><a href="#Page_72">72</a></td></tr>
+<tr><td align='left'>Rocks Being Ground to Flour</td><td align='right'><a href="#Page_73">73</a></td></tr>
+<tr><td align='left'>A Pond Made by a Glacier</td><td align='right'><a href="#Page_88">88</a></td></tr>
+<tr><td align='left'>The Struggle Between a Stream and Its Banks</td><td align='right'><a href="#Page_89">89</a></td></tr>
+<tr><td align='left'>Ripple Marks and Glacial Stri&aelig;</td><td align='right'><a href="#Page_102">102</a></td></tr>
+<tr><td align='left'>Glacial Grooves and Markings</td><td align='right'><a href="#Page_103">103</a></td></tr>
+<tr><td align='left'>Crinoid and Ammonite</td><td align='right'><a href="#Page_140">140</a></td></tr>
+<tr><td align='left'>Fossil Corals, Coquina, Hippurite Limestone</td><td align='right'><a href="#Page_141">141</a></td></tr>
+<tr><td align='left'>Fossil Fish</td><td align='right'><a href="#Page_152">152</a></td></tr>
+<tr><td align='left'>Meteorite</td><td align='right'><a href="#Page_153">153</a></td></tr>
+<tr><td align='left'>Eocene Fish and Trilobite</td><td align='right'><a href="#Page_156">156</a></td></tr>
+<tr><td align='left'>How Coal Was Made</td><td align='right'><a href="#Page_157">157</a></td></tr>
+<tr><td align='left'>Banded Sandstone. Opalized Wood</td><td align='right'><a href="#Page_176">176</a></td></tr>
+<tr><td align='left'>Allosaurus</td><td align='right'><a href="#Page_177">177</a></td></tr>
+<tr><td align='left'>A Three-horned Dinosaur</td><td align='right'><a href="#Page_178">178</a></td></tr>
+<tr><td align='left'>Remains of Brontosaurus</td><td align='right'><a href="#Page_179">179</a></td></tr>
+<tr><td align='left'>Restoration of Brontosaurus</td><td align='right'><a href="#Page_182">182</a></td></tr>
+<tr><td align='left'>Ornitholestes, a Small Dinosaur</td><td align='right'><a href="#Page_183">183</a></td></tr>
+<tr><td align='left'>A Mammoth</td><td align='right'><a href="#Page_186">186</a></td></tr>
+<tr><td align='left'>An Ancestor of the Horse</td><td align='right'><a href="#Page_187">187</a></td></tr>
+<tr><td align='left'>Orion, His Dogs, and the Bull</td><td align='right'><a href="#Page_214">214</a></td></tr>
+<tr><td align='left'>Other Fanciful Sketches of Constellations</td><td align='right'><a href="#Page_215">215</a></td></tr>
+<tr><td align='left'>The Sky in Winter</td><td align='right'><a href="#Page_244">244</a></td></tr>
+<tr><td align='left'>The Sky in Spring</td><td align='right'><a href="#Page_244">244</a></td></tr>
+<tr><td align='left'>The Sky in Summer</td><td align='right'><a href="#Page_244">244</a></td></tr>
+<tr><td align='left'>The Sky in Autumn</td><td align='right'><a href="#Page_244">244</a></td></tr>
+</table></div><p><span class='pagenum'><a name="Page_1" id="Page_1">[Pg 1]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="PART_I" id="PART_I"></a>PART I</h2>
+
+<h3>THE EARTH</h3>
+
+<p><span class='pagenum'><a name="Page_2" id="Page_2">[Pg 2]</a></span></p>
+<hr style='width: 45%;' />
+<p><span class='pagenum'><a name="Page_3" id="Page_3">[Pg 3]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_GREAT_STONE_BOOK" id="THE_GREAT_STONE_BOOK"></a>THE GREAT STONE BOOK</h2>
+
+<div class="blockquot"><p>"The crust of our earth is a great cemetery where the rocks
+are tombstones on which the buried dead have written their
+own epitaphs. They tell us who they were, and when and where
+they lived."&mdash;<i>Louis Agassiz.</i></p></div>
+
+
+<p>Deep in the ground, and high and dry on the sides of mountains, belts of
+limestone and sandstone and slate lie on the ancient granite ribs of the
+earth. They are the deposits of sand and mud that formed the shores of
+ancient seas. The limestone is formed of the decayed shells of animal
+forms that flourished in shallow bays along those shores. And all we
+know about the life of these early days is read in the epitaphs written
+on these stone tables.</p>
+
+<p>Under the stratified rocks, the granite foundations tell nothing of life
+on the earth. But the sea rolled over them, and in it lived a great
+variety of shellfish. Evidently the earliest fossil-bearing rocks were
+worn away, for the rocks that now lie on the granite show not the
+beginnings, but the high tide of life. The "lost interval" of which
+geologists speak was a time when living forms were few in the sea.</p>
+
+<p>In the muddy bottoms of shallow, quiet bays lie the shells and skeletons
+of the creatures that live their lives in those waters and die when they
+grow<span class='pagenum'><a name="Page_4" id="Page_4">[Pg 4]</a></span> old and feeble. We have seen the fiddler crabs by thousands on
+such shores, young and old, lusty and feeble. We have seen the rocks
+along another coast almost covered by the coiled shells of little gray
+periwinkles, and big clumps of black mussels hanging on the piers and
+wharfs. All these creatures die, at length, and their shells accumulate
+on the shallow sea bottom. Who has not spent hours gathering dead shells
+which the tide has thrown up on the beach? Who has not cut his foot on
+the broken shells that lie in the sandy bottom we walk on whenever we go
+into the surf to swim or bathe?</p>
+
+<p>Read downward from the surface toward the earth's centre&mdash;</p>
+
+<div class='padding'>
+<p class='center'><span class="smcap">Table of Contents</span></p>
+
+
+<div class='center'>
+<table border="0" cellpadding="4" cellspacing="0" summary="">
+<tr><td align='left'>Part</td><td align='left'></td><td align='center' colspan='3'><i>Rock Systems</i></td><td align='left'><i>Dominant Animals</i></td><td align='left'><i>Dominant Plants</i></td></tr>
+<tr><td align='left'>VII.</td><td align='left'></td><td align='left'>Recent</td><td align='left'></td><td align='left'></td><td align='left'>Man</td><td align='left'>Flowering kinds</td></tr>
+<tr><td align='left'></td><td align='left' rowspan='3'><span class='triple'>{</span></td><td align='left'>Quaternary</td></tr>
+<tr><td align='left'>VI.</td><td align='left'></td><td align='left' rowspan='3'><span class='triple'>{</span></td><td align='left'>Pliocene</td><td align='left'>Mammals</td><td align='left'>Early flowering</td></tr>
+<tr><td align='left'></td><td align='left'>Tertiary</td><td align='left'>Miocene</td></tr>
+<tr><td align='left'></td><td align='left'></td><td align='left'></td><td align='left'>Eocene</td></tr>
+<tr><td align='left'>V.</td><td align='left'></td><td align='left'>Mesozoic</td><td align='left'></td><td align='left'></td><td align='left'>Reptiles</td><td align='left'>Cycads</td></tr>
+<tr><td align='left'>IV.</td><td align='left'></td><td align='left'>Carboniferous</td><td align='left'></td><td align='left'></td><td align='left'>Amphibians</td><td align='left'>Ferns and Conifers</td></tr>
+<tr><td align='left'>III.</td><td align='left'></td><td align='left'>Devonian</td><td align='left'></td><td align='left'></td><td align='left'>Fishes</td><td align='left'>Ferns</td></tr>
+<tr><td align='left'>II.</td><td align='left'></td><td align='left'>Silurian</td><td align='left'></td><td align='left'></td><td align='left'>Molluscs</td><td align='left'>Seaweeds</td></tr>
+<tr><td align='left'>I.</td><td align='left'></td><td align='left'>Fire-formed</td><td align='left'></td><td align='left'></td><td align='left'>No life</td><td align='left'>No life</td></tr>
+</table></div></div>
+
+<p>It is by dying that the creatures of the sea write their epitaphs. The
+mud or sand swallows them up. In time these submerged banks may be left
+dry, and become beds of stone. Then some of the skeletons<span class='pagenum'><a name="Page_5" id="Page_5">[Pg 5]</a></span> and shells
+may be revealed in blocks of quarried stone, still perfect in form after
+lying buried for thousands of years.</p>
+
+<p>The leaves of this great stone book are the layers of rock, laid down
+under water. Between the leaves are pressed specimens&mdash;fossils of
+animals and plants that have lived on the earth.<span class='pagenum'><a name="Page_6" id="Page_6">[Pg 6]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_FOSSIL_FISH" id="THE_FOSSIL_FISH"></a>THE FOSSIL FISH</h2>
+
+
+<p>I remember seeing a flat piece of stone on a library table, with the
+skeleton of a fish distinctly raised on one surface. The friend who
+owned this strange-looking specimen told me that she found it in a stone
+quarry. She brought home a large piece of the slate, and a stone-mason
+cut out the block with the fish in it, and her souvenir made a useful
+and interesting paper-weight.</p>
+
+<p>The story of that fish I heard with wonder, and have never forgotten. I
+had never heard of fossil animals or plants until my good neighbour
+talked about them. She showed me bits of stone with fern leaves pressed
+into them. One piece of hard limestone was as full of little sea-shells
+as it could possibly be. One ball of marble was a honeycombed pattern,
+and called "fossil coral."</p>
+
+<p>The fossil fish was once alive, swimming in the sea, and feeding on the
+things it liked to eat, as all happy fishes do. Near shore a river
+poured its muddy water into the sea, and the sandy bottom was covered
+with the mud that settled on it. At last the fish grew old, and perhaps
+a trifle stupid about catching minnows. It died, and sank to the muddy
+floor of the sea. Its horny bones were not<span class='pagenum'><a name="Page_7" id="Page_7">[Pg 7]</a></span> dissolved by the water. They
+remained, and the mud filtered in and filled all the spaces. Soon the
+fish was buried completely by the sediment the river brought.</p>
+
+<p>Years, thousands of them, went by, and the layer of mud was so thick and
+heavy above the skeleton of the fish that it bore a weight of tons
+there, under the water. The close-packed mud became a stiff clay. After
+more thousands of years, the sea no longer came so far ashore, for the
+river had built up a great delta of land out of mud. The clay in which
+the fish was hidden hardened into slate. Water crept down in the loose
+upper layers, dissolving out salt and other minerals, and having harder
+work to soak through, the lower it went. The water left some of the
+minerals it had accumulated, calcium and silica and iron, in the lower
+rock beds, making them harder than they were before, and heavier and
+less porous.</p>
+
+<p>When the river gorge was cut through these layers of rock, the colour
+and thickness of each kind were laid bare. Centuries after, perhaps
+thousands of years, indeed, the quarrymen cut out the layers fit for
+building stones, flags for walks and slates for roofing. In the
+splitting of a flagstone, the long-buried skeleton of the fish came to
+light.</p>
+
+<p>Under our feet the earth lies in layers. Under the soil lie loose beds
+of clay and sand and gravel, and under these loose kinds of earth are
+close-packed clays, sandstones, limestones, shales, often strangely<span class='pagenum'><a name="Page_8" id="Page_8">[Pg 8]</a></span>
+tilted away from the horizontal line, but variously fitted, one layer to
+another. Under these rocks lie the foundations of the earth&mdash;the
+fire-formed rocks, like granite. The depth of this original rock is
+unknown. It is the substance out of which the earth is made, we think.
+All the layered rocks are made of particles of the older ones, stolen by
+wind and water, and finally deposited on the borders of lakes and seas.
+So our rivers are doing to-day what they have always done&mdash;they are
+tearing down rocks, grinding and sifting the fragments, and letting them
+fall where the current of fresh water meets a great body of water that
+is still, or has currents contrary to that of the river.</p>
+
+<p>Do you see a little dead fish in the water? It is on the way to become a
+fossil, and the mud that sifts over it, to become a layer of slate.
+Every seashore buries its dead in layers of sand and mud.<span class='pagenum'><a name="Page_9" id="Page_9">[Pg 9]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_CRUST_OF_THE_EARTH" id="THE_CRUST_OF_THE_EARTH"></a>THE CRUST OF THE EARTH</h2>
+
+
+<p>It is hard to believe that our solid earth was once a ball of seething
+liquid, like the red-hot iron that is poured out of the big clay cups
+into the sand moulds at an iron foundry. But when a mountain like
+Vesuvius sets up a mighty rumbling, and finally a mass of white-hot lava
+bursts from the centre and streams down the sides, covering the
+vineyards and olive orchards, and driving the people out of their homes
+in terror, it seems as if the earth's crust must be but a thin and frail
+affair, covering a fiery interior, which might at any time break out.
+The people who live near volcanoes might easily get this idea.</p>
+
+<p>But they do not. They go back as soon as the lava streams are cooled,
+and rebuild their homes, and plant more orchards and vineyards. "It is
+<i>so</i> many years," say they to one another, "since the last bad eruption.
+Vesuvius will probably sleep now till we are dead and gone."</p>
+
+<p>This is good reasoning. There are few active volcanoes left on the
+earth, compared with the number that were once active, and long ago
+became extinct. And the time between eruptions of the active ones grows
+longer; the eruptions less violent. Terrible as were the recent
+earthquakes of San<span class='pagenum'><a name="Page_10" id="Page_10">[Pg 10]</a></span> Francisco and Messina, this form of disturbance of
+the earth's crust is growing constantly less frequent. The earth is
+growing cooler as it grows older; the crust thickens and grows stronger
+as centuries pass. We have been studying the earth only a few hundred
+years. The crust has been cooling for millions of years, and
+mountain-making was the result of the shrinking of the crust. That
+formed folds and clefts, and let masses of the heated substance pour out
+on the surface.</p>
+
+<p>My first geography lesson I shall never forget. The new teacher had very
+bright eyes and <i>such</i> pretty hands! She held up a red apple, and told
+us that the earth's substance was melted and burning, inside its crust,
+which was about as thick, in proportion to the size of the globe, as the
+skin of the apple. I was filled with wonder and fear. What if we
+children jumped the rope so hard as to break through the fragile shell,
+and drop out of sight in a sea of fiery metal, like melted iron? Some of
+the boys didn't believe it, but they were impressed, nevertheless.</p>
+
+<p>The theory of the heated interior of the earth is still believed, but
+the idea that flames and bubbling metals are enclosed in the outer layer
+of solid matter has generally been abandoned. The power that draws all
+of its particles toward the earth's centre is stated by the laws of
+gravitation. The amount of "pull" is the measure of the weight of any
+substance. Lift a stone, and then a feather pillow, much larger<span class='pagenum'><a name="Page_11" id="Page_11">[Pg 11]</a></span> than
+the stone. One is strongly drawn to the earth; the other not. One is
+<i>heavy</i>, we say, the other <i>light</i>.</p>
+
+<p>If a stone you can pick up is heavy, how much heavier is a great boulder
+that it takes a four-horse team to haul. What tremendous weight there is
+in all the boulders scattered on a hillside! The hill itself could not
+be made level without digging away thousands of tons of earth. The
+earth's outer crust, with its miles in depth of mountains and level
+ground, is a crushing weight lying on the heated under-substance. Every
+foot of depth adds greatly to the pressure exerted upon the mass, for
+the attraction of gravitation increases amazingly as the centre of the
+earth is approached.</p>
+
+<p>It is now believed that the earth is solid to its centre, though heated
+to a high degree. Terrific pressure, which causes this heat, is exerted
+by the weight of the crust. A crack in the crust may relieve this
+pressure at some point, and a mass of substance may be forced out and
+burst into a flaming stream of lava. Such an eruption is familiar in
+volcanic regions. The fact that red-hot lava streams from the crater of
+Vesuvius is no proof that it was seething and bubbling while far below
+the surface.</p>
+
+<p>Volcanoes, geysers, and hot springs prove that the earth's interior is
+hot. The crust is frozen the year around in the polar regions, and never
+between the Tropics of Cancer and Capricorn. The sun's rays produce our
+different climates, but they affect only the surface. Underground, there
+is a rise of a<span class='pagenum'><a name="Page_12" id="Page_12">[Pg 12]</a></span> degree of temperature for every fifty feet one goes
+down. The lowest mine shaft is about a mile deep. That is only one
+four-thousandth of the distance to the earth's centre.</p>
+
+<p>By an easy computation we could locate the known melting-point for
+metals and other rock materials. But one degree for each fifty feet of
+depth below the surface may not be correct for the second mile, as it is
+for the first. Again, the melting-point is probably a great deal higher
+for substances under great pressure. The weight of the crust is a burden
+the under-rocks bear. Probably the pressure on every square inch reaches
+thousands of tons. Could any substance become liquid with such a weight
+upon it, whatever heat it attained? Nobody can answer this question.</p>
+
+<p>The theory that volcanoes are chimneys connecting lakes of burning lava
+with the surface of the earth is discredited by geologists. The weight
+of the overlying crust would, they think, close such chambers, and
+reduce liquids to a solid condition.</p>
+
+<p>Since the first land rose above the sea, the crust of the earth has
+gradually become more stable, but even now there is scarcely a day when
+the instruments called seismographs do not record earthquake shocks in
+some part of the earth; and the outbreaks of Vesuvius and &AElig;tna, the
+constant boiling of lava in the craters of the Hawaiian Islands and
+other volcanic centres, prove that even now the earth's crust is very
+thin and unstable. The further<span class='pagenum'><a name="Page_13" id="Page_13">[Pg 13]</a></span> back in time we go, the thinner was the
+crust, the more frequent the outbursts of volcanic activity, the more
+readily did wrinkles form.</p>
+
+<p>The shores of New Jersey and of Greenland are gradually sinking, and the
+sea coming up over the land. Certain parts of the world are gradually
+rising out of the sea. In earlier times the rising or the sinking of
+land over large areas happened much more frequently than now.<span class='pagenum'><a name="Page_14" id="Page_14">[Pg 14]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="WHAT_IS_THE_EARTH_MADE_OF" id="WHAT_IS_THE_EARTH_MADE_OF"></a>WHAT IS THE EARTH MADE OF?</h2>
+
+
+<p>"Baking day" is a great institution in the comfortable farm life of the
+American people. The big range oven is not allowed to grow cold until
+rows of pies adorn the pantry shelves, and cakes, tarts, and generous
+loaves of bread are added to the store. Cookies, perhaps, and a big pan
+full of crisp, brown doughnuts often crown the day's work. No gallery of
+art treasures will ever charm the grown-up boys and girls as those
+pantry shelves charmed the bright-eyed, hungry children, who were
+allowed to survey the treasure-house, and sample its good things while
+they were still warm.</p>
+
+<p>You could count a dozen different kinds of cakes and pies, rolls and
+cookies on those pantry shelves, yet several of them were made out of
+the same dough. Instead of a loaf of bread, mother could make two or
+three kinds of coffee cake, or cinnamon rolls, or currant buns, or
+Parker-House rolls. Even the pastry, which made the pies and tarts, was
+not so different from the bread dough, for each was made of flour, and
+contained, besides the salt, "shortening," which was butter or lard.
+Sugar was used in everything, from the bread, which had a
+table-spoonful,<span class='pagenum'><a name="Page_15" id="Page_15">[Pg 15]</a></span> to the cookies, which were finished with a sifting of
+sugar on top.</p>
+
+<p>How much of the food we eat is made of a very few staple
+foodstuffs,&mdash;starch, sugar, fats! So in the wonderful earth and all that
+grows out of it and lives upon it. Only seventy different elements have
+been discovered, counting, besides the earth, the water and the air, and
+even the strange wandering bodies, called meteorites, that fall upon the
+earth out of the sky. Like the flour in the different cakes and pies,
+the element carbon is found in abundance and in strangely different
+combinations. As a gas, in combination with oxygen, it is breathed out
+of our lungs, and out of chimneys where coal and wood are burned. It
+forms a large part of the framework of trees and other plants, and
+remains as charcoal when the wood is slowly burned under a close
+covering. There is a good proportion of carbon in animal bodies, in the
+bones as well as the soft parts, and carbon is plentiful in the mineral
+substances of the earth.</p>
+
+<p>The chemist is the man who has determined for us the existence and the
+distribution of the seventy elements. He finds them in the solid
+substances of the globe and in the water that covers four-fifths of its
+surface; in the atmosphere that covers sea and land, and in all the
+living forms of plants and animals that live in the seas and on the
+land. By means of an instrument called the spectroscope, the heavenly
+bodies are proved to be made of the same substances<span class='pagenum'><a name="Page_16" id="Page_16">[Pg 16]</a></span> that are found in
+the rocks. The sun tells what it is made of, and one proof that the
+earth is a child of the sun is in the fact that the same elements are
+found in the substance of both.</p>
+
+<p>Of the seventy elements, the most important are these: Oxygen, silicon,
+aluminum, iron, manganese, calcium, magnesium, potassium, sodium,
+carbon, hydrogen, phosphorus, sulphur, chlorine, nitrogen.</p>
+
+<p><i>Oxygen</i> is the most plentiful and the most important element. One-fifth
+of the air we breathe is oxygen; one-third of the water we drink. The
+rock foundations of the earth are nearly one-half oxygen. No fire can
+burn, no plant or animal can grow, or even decay after it dies, unless
+oxygen is present and takes an active part in each process. Strangely
+enough, this wonderful element is invisible. We open a window, and pure
+air, rich in oxygen, comes in and takes the place of the bad air but we
+cannot see the change. Water we see, but if the oxygen and the hydrogen
+which compose the colourless liquid were separated, each would become at
+once an invisible gas. The oxygen of solid rocks exists only in
+combination with other elements.</p>
+
+<p><i>Silicon</i> is the element which, united with oxygen, makes the rock
+called quartz. On the seashore the children are busy with their pails
+and shovels digging in the white, clean sand. These grains are of
+quartz,&mdash;fine crystals of a rock which forms nearly three-quarters of
+the solid earth's substance. Not<span class='pagenum'><a name="Page_17" id="Page_17">[Pg 17]</a></span> only in rocks, but out here in the
+garden, the soil is full of particles of sand. You cannot get away from
+it.</p>
+
+<p><i>Aluminum</i> is a light, bluish-white metal which we know best in
+expensive cooking utensils. It is more abundant even than iron, but
+processes of extracting it from the clay are still expensive. It is
+oftenest found in combination with oxygen and silicon. While nearly
+one-tenth of the earth's crust is composed of the metal aluminum,
+four-fifths and more is composed of the minerals called silicates of
+aluminum&mdash;oxygen, silicon, and aluminum in various combinations. It is
+more plentiful than any other substance in rocks and in the clays and
+ordinary soils, which are the finely ground particles of rock material.</p>
+
+<p><i>Iron</i> is one of the commonest of elements. We know it by its red
+colour. A rusty nail is covered with oxide of iron, a combination which
+is readily formed wherever iron is exposed to the action of water or
+air. You have seen yellowish or red streaks in clefts of the rocks. This
+shows where water has dissolved out the iron and formed the oxide. The
+red colour of New Jersey soil is due to the iron it contains. Indeed,
+the whole earth's crust is rich in iron which the water easily
+dissolves. The roots of plants take up quantities of iron in solution
+and this mounts to the blossoms, leaves, and fruit. The red or yellow
+colour of autumn leaves, of apples, of strawberries, of tulips, and of
+roses, is produced by iron. The rosy cheeks of children are due to<span class='pagenum'><a name="Page_18" id="Page_18">[Pg 18]</a></span> iron
+in the food they eat and in the water they drink. The doctor but follows
+the suggestion of nature when he gives a pale and listless person a
+tonic of iron to make his blood red.</p>
+
+<p>Iron is rarely found free, but it forms about five per cent. of the
+crust of the earth, and it is believed to form at least one-fifth of the
+unknown centre of the earth, the bulk of the globe, the weight of which
+we know, but concerning the substance of which we can say little that is
+positive.</p>
+
+<p><i>Manganese</i> is not a conspicuous element, but is found united with
+oxygen in purplish or black streaks on the sides of rocks. It is
+somewhat like iron, but much less common.</p>
+
+<p><i>Calcium</i> is the element that is the foundation of limestones. The
+skeletons and shells of animals are made of calcite, a common mineral
+formed by the uniting of carbon, oxygen, and calcium. Marbles are,
+perhaps, the most permanent form of the limestone rocks. "Hard" water
+has filtered through rocks containing calcite, and absorbed particles of
+this mineral. From water thus impregnated, all animal life on the earth
+obtains its bone-building and shell-building materials.</p>
+
+<p><i>Carbon</i> forms a large part of the tissues of plants and animals, and in
+the remains of these it is chiefly found in the earth's crust. When
+these burn or decay, the carbon remains as charcoal or escapes to the
+air in union with oxygen as the well known carbonic acid gas. This is
+one of the most important<span class='pagenum'><a name="Page_19" id="Page_19">[Pg 19]</a></span> foods of plants. Joined with calcium it forms
+the mineral calcite, or carbonate of lime.</p>
+
+<p><i>Hydrogen</i> is one of the two gases that unite to form water. Oxygen is
+the other. Many kinds of rock contain a considerable amount of water.
+Surface water sinks into porous soils and rocks, and accumulates in
+pockets and veins which feed springs, and are the reserve water supply
+that keeps our rivers flowing, even through dry weather. More water is
+held by absorption in the earth's solid crust than in all the oceans and
+seas and great lakes.</p>
+
+<p>Hydrogen, combined with carbon, occurs in solid rocks where the remains
+of plants and animals have slowly decayed. From such processes the
+so-called hydrocarbons, rock oil and natural gas, have accumulated. When
+such decay goes on above ground, these valuable products escape into the
+air. Marsh gas, whose feeble flame above decaying vegetation is the
+will-o'-the-wisp of swamps, is an example.</p>
+
+<p><i>Magnesium</i>, <i>potassium</i>, and <i>sodium</i> are found in equal quantities in
+the earth's crust, but never free. In union with chlorine, each forms a
+soluble salt, and is thus found in water. Common salt, chloride of
+sodium, is the most abundant of these. Water dissolves salt out of the
+rocks, and carries it into the sea. Clouds that rise by the evaporation
+of ocean water leave the salt behind, hence the seas are becoming more
+and more salty, for the rivers carry salt to the oceans, which hold fast
+all they get.</p>
+
+<p><i>Phosphorus</i> is an element found united with oxygen<span class='pagenum'><a name="Page_20" id="Page_20">[Pg 20]</a></span> in the tissues of
+both plants and animals. It is most abundant in bones. Rocks containing
+fossil bones are rich in lime phosphates, which are important commercial
+fertilizers for enriching the soil. Beds of these rocks are found and
+mined in South Carolina and elsewhere.</p>
+
+<p><i>Sulphur</i> is well known as a yellow powder found most plentifully in
+rocks that are near volcanoes. It is a needed element in plant and
+animal bodies. It occurs in rocks, united with many different elements.
+In union with oxygen and a metal it forms the group of minerals called
+sulphates. In union with iron it forms sulphide of iron. The "fool's
+gold" which Captain John Smith's colonists found in the sand at
+Jamestown, was this worthless iron pyrites.</p>
+
+<p><i>Chlorine</i> is a greenish, yellow gas, very heavy, and dangerous to
+inhale. If it gets into the lungs, it settles into the lowest levels,
+and one must stand on one's head to get it out. As an element of the
+earth's crust it is not very plentiful, but it is a part of all the
+chlorides of sodium, magnesium, and potassium. In salt, it forms two per
+cent. of the sea water. It is much less abundant in the rocks.</p>
+
+<p>To these elements we might add <i>nitrogen</i>, that invisible gas which
+forms nearly four-fifths of our atmosphere, and is a most important
+element of plant food in the soil. Most of the seventy elements are very
+rare. Many are metals, like gold and iron and silver. Some are not<span class='pagenum'><a name="Page_21" id="Page_21">[Pg 21]</a></span>
+metals. Some are solid. A few are liquid, like the metal mercury, and
+several are gaseous. Some are free and pure, and show no disposition to
+unite with others. Nuggets of gold are examples of this. Some exist only
+in union with other elements. This is the common rule among the
+elements. Changes are constantly going on. The elements are constantly
+abandoning old partnerships and forming new ones. Growth and decay of
+plant and animal life are but parts of the great programme of constant
+change which is going on and has been in progress since the world
+began.<span class='pagenum'><a name="Page_22" id="Page_22">[Pg 22]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_FIRST_DRY_LAND" id="THE_FIRST_DRY_LAND"></a>THE FIRST DRY LAND</h2>
+
+
+<p>When the earth's crust first formed it was still hot, though not so hot
+as when it was a mass of melted, glowing substance. As it moved through
+the cold spaces of the sky, it lost more heat and its crust became
+thicker. At length the cloud masses became condensed enough to fall in
+torrents of water, and a great sea covered all the land. This was before
+any living thing, plant or animal, existed on our planet. Can you
+imagine the continents and islands that form the land part of a map or
+globe suddenly overwhelmed by the oceans, the names and boundaries of
+which you have taken such pains to learn in the study of geography? The
+globe would be one blank of blue water, and geography would be
+abolished&mdash;and there would be nobody to study it. Possibly the fishes in
+the sea might not notice any change in the course of their lives, except
+when they swam among the ruins of buried cities and peered into the
+windows of high buildings, or wondered what new kind of seaweed it was
+when they came upon a submerged forest.</p>
+
+<p>In that old time of the great sea that covered the globe, we are told
+that there was a dense atmosphere over the face of the deep. So things
+were shaping<span class='pagenum'><a name="Page_23" id="Page_23">[Pg 23]</a></span> themselves for the far-off time when life should exist,
+not only in the sea, where the first life did appear, but on land. But
+it took millions of years to fit the earth for living things.</p>
+
+<p>The cooling of the earth made it shrink, and the crust began to be
+folded into gentle curves, as the skin of a shrunken apple becomes
+wrinkled on the flesh. Some of these creases merely changed the depth of
+water on the sea bottom; but one ridge was lifted above the water. The
+water parted and streamed down its sloping sides, and a granite reef,
+which shone in the sunshine, became the first dry land. It lay east and
+west, and stretched for many miles. It is still dry land and is a part
+of our own continent. Now it is but a small part of the country, but it
+is known by geologists, who can tell its boundaries, though newer land
+joins it on every side. It is named the Laurentian Hills, on geological
+maps. Its southern border reaches along the northern boundary of the
+Great Lakes to the head-waters of the Mississippi River.</p>
+
+<p>From this base, two ridges are lifted, forming a colossal V. One extends
+northeast to Nova Scotia; the other northwest to the Arctic seas. The V
+encloses Hudson Bay.</p>
+
+<p>Besides this first elongated island of bare rocks, land appeared in a
+strip where now the Blue Ridge Mountains stretch from New England to
+Georgia. The other side of the continent lifted up two folds of the
+crust above sea level. They are the main<span class='pagenum'><a name="Page_24" id="Page_24">[Pg 24]</a></span> ridges of the Colorado and the
+Wasatch Mountains. Possibly the main ridge of the Sierra Nevada rose
+also at this time. The Ozark group of mountains, too, showed as a few
+island peaks above the sea.</p>
+
+<p>These first rocks were rapidly eaten away, for the atmosphere was not
+like ours, but heavily charged with destructive gases, which did more,
+we believe, to disintegrate the exposed rock surfaces than did the two
+other forces, wind and water, combined. The sediment washed down to the
+sea by rains, accumulated along the shores, filling the shallows and
+thus adding to the width of the land areas. The ancient granite ridge of
+the Laurentian Hills is now low, and slopes gently. This is true of all
+very old mountains. The newer ones are high and steep. It takes time to
+grind down the peaks and carry off the waste material loosened by
+erosion.</p>
+
+<p>Far more material than could have been washed down the slopes of the
+first land ridges came directly from the interior of the earth, and
+spread out in vast, submarine layers upon the early crust. Volcanic
+craters opened under water, and poured out liquid mineral matter, that
+flowed over the sea bottom before it cooled. Imagine the commotion that
+agitated the water as these submerged chimneys blew off their lids, and
+discharged their fiery contents! It was long before the sea was cool
+enough to be the home of living things.</p>
+
+<p>The layers of rock that formed under the sea during this period of the
+earth's history are of enormous<span class='pagenum'><a name="Page_25" id="Page_25">[Pg 25]</a></span> thickness. They were four or five miles
+deep along the Laurentian Hills. They broadened the original granite
+ridge by filling the sea bottom along the shores. The backbones of the
+Appalachian system and the Cordilleras were built up in the same
+way&mdash;the oldest rocks were worn away, and their d&eacute;bris built up newer
+ones in strata.</p>
+
+<p>When these layers of rock became dry land, the earth's crust was much
+more stable and cool than it had ever been before. The vast
+rock-building of that era equals all that has been done since. The
+layers of rocks formed since then do not equal the total thickness of
+these first strata. So we believe that the time required to build those
+Arch&aelig;an rock foundations equals or surpasses the vast period that has
+elapsed since the Arch&aelig;an strata were formed.</p>
+
+<p>The northern part of North America has grown around those old granite
+ridges by the gradual rising of the shores. The geologist may walk along
+the Laurentian Hills, that parted the waters into a northern and a
+southern ocean. He crosses the rocky beds deposited upon the granite;
+then the successive beds formed as the land rose and the ocean receded.
+Age after age is recorded in the rocks. Gradually the sea is crowded
+back, and the land masses, east, west, and north, meet to form the
+continent. Nowhere on the earth are the steps of continental growth
+shown in unbroken sequence as they are in North America.<span class='pagenum'><a name="Page_26" id="Page_26">[Pg 26]</a></span></p>
+
+<p>How long ago did those first islands appear above the sea? Nobody
+ventures a definite answer to this question. No one has the means of
+knowing. But those who know most about it estimate that at the least one
+hundred million years have passed since then&mdash;one hundred thousand
+thousand years!<span class='pagenum'><a name="Page_27" id="Page_27">[Pg 27]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="A_STUDY_OF_GRANITE" id="A_STUDY_OF_GRANITE"></a>A STUDY OF GRANITE</h2>
+
+
+<p>In Every village cemetery it is easy to find shafts of gray or speckled
+granite, the polished surfaces of which show that the granite is made of
+small bits of different coloured minerals, cemented together into solid
+rock. Outside the gate you will usually find a place where monuments and
+gravestones may be bought. Here there is usually a stonecutter chipping
+away on a block with his graving tools. He is a man worth knowing, and
+because his work is rather monotonous he will probably be glad to talk
+to a chance visitor and answer questions about the different kinds of
+stone on which he works.</p>
+
+<p>There are bits of granite lying about on the ground. If you have a
+hand-glass of low power, such as the botany class uses to examine the
+parts of flowers, it will be interesting to look through it and see the
+magnified surface of a flake of broken granite. Here are bits of glassy
+quartz, clear and sparkling in the sun. Black and white may be all the
+colours you make out in this specimen, or it may be that you see specks
+of pink, dark green, gray, and smoky brown, all cemented together with
+no spaces that are not filled. The particles of quartz are of various
+colours, and are very hard. They scratch glass,<span class='pagenum'><a name="Page_28" id="Page_28">[Pg 28]</a></span> and you cannot scratch
+them with the steel point of your knife, as you can scratch the other
+minerals associated with the grains of quartz.</p>
+
+<p>Granite is made of quartz, feldspar, and mica, sometimes with added
+particles of hornblende. Feldspar particles have as wide a range of
+colour as quartz, but it is easy to tell the two apart. A knife will
+scratch feldspar, as it is not so hard as quartz. The crystals of
+feldspar have smooth faces, while quartz breaks with a rough surface as
+glass does. Feldspar loses its glassy lustre when exposed to the
+weather, and becomes dull, with the soft lustre of pearl.</p>
+
+<p>Mica may be clear and glassy, and it ranges in colour from transparency
+through various shades of brown to black. It has the peculiarity of
+splitting into thin, leaf-like, flexible sheets, so it is easy to find
+out which particles in a piece of granite are mica. One has only to use
+one's pocket knife with a little care. Hornblende is a dark mineral
+which contains considerable iron. It is found in lavas and granites,
+where it easily decays by the rusting of the iron. It is not unusual to
+see a rough granite boulder streaked with dark red rust from this cause.</p>
+
+<p>The crumbling of granite is constantly going on as a result of the
+exposure of its four mineral elements to the air. Quartz is the most
+stable and resistant to weathering. Soil water trickling over a granite
+cliff has little effect on the quartz particles; but it dissolves out
+some of the silicon. The bits of feldspar<span class='pagenum'><a name="Page_29" id="Page_29">[Pg 29]</a></span> are even more resistant to
+water than quartz is, but the air causes them to decay rapidly, and
+finally to fall away in a sort of mealy clay. Mica, like feldspar,
+decays easily. Its substance is dissolved by water and carried away to
+become a kind of clay. The hornblende rusts away chiefly under the
+influence of moist air and trickling water.</p>
+
+<p>We think of granite as a firm, imperishable kind of rock, and use it in
+great buildings like churches and cathedrals that are to stand for
+centuries. But the faces that are exposed to the air suffer, especially
+in regions having a moist climate. The signs of decay are plainly
+visible on the outer surfaces of these stones. Fortunate it is that the
+weathering process cannot go very deep.</p>
+
+<p>The glassy polish on a smooth granite shaft is the silicon which acts as
+a cement to bind all the particles together. It is resistant to the
+weather. A polished shaft will last longer than an unpolished one.</p>
+
+<p>Granites differ in colouring because the minerals that compose them, the
+feldspars, quartzes, micas, and hornblendes, have each so wide a range
+of colour. Again, the proportions of the different mineral elements vary
+greatly in different granites. A banded granite the colours of which
+give it a stratified appearance is called a gneiss.</p>
+
+<p>We have spoken before of the seventy elements found in the earth's
+crust. A mineral is a union of two or more of these different elements;
+and we<span class='pagenum'><a name="Page_30" id="Page_30">[Pg 30]</a></span> have found four minerals composing our granite rock. It may be
+interesting to go back and inquire what elements compose these four
+minerals. Quartz is made of silicon and oxygen. Feldspar is made of
+silicon, oxygen, and aluminum. Mica is made of silicon, oxygen, and
+carbon, with some mingling of potassium and iron and other elements in
+differing proportions. Hornblende is made of silicon, oxygen, carbon,
+and iron.</p>
+
+<p>The crumbling of a granite rock separates the minerals that compose it,
+reducing some to the condition of clay, others to grains of sand. Some
+of the elements let go their union and become free to form new unions.
+Water and wind gather up the fragments of crumbling granite and carry
+them away. The feldspar and mica fragments form clay; the quartz
+fragments, sand. All of the sandstones and slates, the sand-banks and
+sand beaches, are made out of crumbled granite, the rocky foundations of
+the earth.<span class='pagenum'><a name="Page_31" id="Page_31">[Pg 31]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="METAMORPHIC_ROCKS" id="METAMORPHIC_ROCKS"></a>METAMORPHIC ROCKS</h2>
+
+
+<p>In the dawn of life on the earth, soft-bodied creatures, lowest in the
+scale of being, inhabited the sea. The ancient volcanoes the
+subterranean eruptions of which had spread layers of mineral substance
+on the ocean floor, and heated the water to a high degree, had subsided.
+The ocean was sufficiently cool to maintain life. The land was being
+worn down, and its d&eacute;bris washed into the ocean. The first sand-banks
+were accumulating along sandy shores. The finer sediment was carried
+farther out and deposited as mud-banks. These were buried under later
+deposits, and finally, by the rising of the earth's crust, they became
+dry land. Time and pressure converted the sand-banks into sandstones;
+the mud-banks into clay. The remains of living creatures utterly
+disappeared, for they had no hard parts to be preserved as fossils.</p>
+
+<p>The shrinking of the earth's crust had crumpled into folds of the utmost
+complexity those horizontal layers of lava rock poured out on the ocean
+floor. Next, the same forces attacked the thick rock layers formed out
+of sediment&mdash;the aqueous or water-formed sandstones and clays.</p>
+
+<p>The core of the globe contracts, and the force<span class='pagenum'><a name="Page_32" id="Page_32">[Pg 32]</a></span> that crumples the crust
+to fit the core generates heat. The alkaline water in the rocks joins
+with the heat produced by the crumpling and crushing forces, acting
+downward, and from the sides, to transform pure sandstone into glassy
+quartzite, and clay into slate. In other words, water-formed rocks are
+baked until they become fire-formed rocks. They are what the geologist
+calls <i>metamorphic</i>, which means <i>changed</i>.</p>
+
+<p>In many mountainous regions there are breaks through the strata of
+sandstone and slates and limestones, through which streams of lava have
+poured forth from the heated interior. Along the sides of these fissures
+the hot lava has changed all the rocks it touched. The heat of the
+volcanic rock matter has melted the silica in the sand, which has
+hardened again into a crystalline substance like glass.</p>
+
+<p>Have you ever visited a brick-yard? Here men are sifting clay dug out of
+a pit or the side of a hill, adding sand from a sand-bank, and in a big
+mixing box, stirring these two "dry ingredients" with water into a thick
+paste. This dough is moulded into bricks, sun-dried, and then baked in
+kilns themselves built of bricks. At the end of the baking, the soft,
+doughy clay block is transformed into a hard, glassy, or dull brick.
+From aqueous rock materials, fire has produced a metamorphic rock.
+Volcanic action is imitated in this common, simple process of
+brickmaking.<span class='pagenum'><a name="Page_33" id="Page_33">[Pg 33]</a></span></p>
+
+<p>Milwaukee brick is made of clay that has no iron in it. For this reason
+the bricks are yellow after baking. Most bricks are red, on account of
+the iron in the clay, which is converted into a red oxide, or rust, by
+water and heat.</p>
+
+<p>Common flower pots and the tiles used in draining wet land are not
+glazed, as hard-burned bricks are. The baking of these clay things is
+done with much less heat. They are left somewhat porous. But the tiles
+of roofs are baked harder, and get a surface glaze by the melting of the
+glassy particles of the sand.</p>
+
+<p>As bricks vary in colour and quality according to the materials that
+compose them, so the metamorphic rocks differ. The white sand one sees
+on many beaches is largely quartz. This is the substance of pure, white
+sandstone. Metamorphism melts the silica into a glassy liquid cement;
+the particles are bound close together on cooling. The rock becomes a
+white, granular quartzite, that looks like loaf sugar. If banded, it is
+called gneiss. Such rocks take a fine polish.</p>
+
+<p>Pure limestone is also white and granular. When metamorphosed by heat,
+it becomes white marble. The glassy cement that holds the particles of
+lime carbonate shows as the glaze of the polished surface. It is silica.
+One sees the same mineral on the face of polished granite.</p>
+
+<p>Clays are rarely pure. Kaolin is a white clay which, when baked, becomes
+porcelain. China-ware<span class='pagenum'><a name="Page_34" id="Page_34">[Pg 34]</a></span> is artificially metamorphosed kaolin. In the
+early rocks the clay beds were transformed by heat into jasper and
+slates. In beds where clay mingled with sand, in layers, gneiss was
+formed. If mica is a prominent element, the metamorphic rock is easily
+parted into overlapping, scaly layers. It is a mica schist. If
+hornblende is the most abundant mineral, the same scaly structure shows
+in a dark rock called hornblende schist, rich in iron. A schist
+containing much magnesia is called serpentine.</p>
+
+<p>The bricks of the wall, the tiles on the roof, the flower pots on the
+window sill, and the dishes on the breakfast table, are examples of
+metamorphic rocks made by man's skill, by the use of fire and water
+acting on sand and clay. Pottery has preserved the record of
+civilization, from the making of the first crude utensils by cave men to
+the finest expression of decorative art in glass and porcelain.</p>
+
+<p>The choicest material of the builder and the sculptor is limestone baked
+by the fires under the earth's crust into marble. The most enduring of
+all the rocks are the foundation granite, and the metamorphic rocks that
+lie next to them. Over these lie thick layers of sedimentary rocks laid
+down by water. In them the record of life on the earth is written in
+fossils.<span class='pagenum'><a name="Page_35" id="Page_35">[Pg 35]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_AIR_IN_MOTION" id="THE_AIR_IN_MOTION"></a>THE AIR IN MOTION</h2>
+
+
+<p>Most of the beautiful things that surround us and make our lives full of
+happiness appeal to one or more of our five senses. The green trees we
+can see, the bird songs we hear, the perfume of honey-laden flowers we
+smell, the velvety smoothness of a peach we feel, and its rich pulp we
+taste. But over all and through all the things we see and feel and hear
+and taste and smell, is the life-giving air, that lies like a blanket,
+miles in depth, upon the earth. The substance which makes the life of
+plants and animals possible is, when motionless, an invisible,
+tasteless, odourless substance, which makes no sound and is not
+perceptible to the touch.</p>
+
+<p>Air fills the porous substance of the earth's crust for a considerable
+distance, and even the water has so much air in it that fishes are able
+to breathe without coming to the surface. It is not a simple element,
+like gold, or carbon, or calcium, but is made up of several elements,
+chief among which are nitrogen and oxygen. Four-fifths of its bulk is
+nitrogen and one-fifth oxygen. There is present in air more or less of
+watery vapour and of carbon dioxide, the gas which results from the
+burning or decay of any substance. Although no more than<span class='pagenum'><a name="Page_36" id="Page_36">[Pg 36]</a></span> one per cent.
+of the air that surrounds us is water, yet this is a most important
+element. It forms the clouds that bear water back from the ocean and
+scatter it in rain upon the thirsty land. Solid matter in the form of
+dust, and soot from chimneys, accumulates in the clouds and does a good
+work in condensing the moisture and causing it to fall.</p>
+
+<p>It is believed that the air reaches to a height of one hundred to two
+hundred miles above the earth's surface. If a globe six feet in diameter
+were furnished with an atmosphere proportionately as deep as ours, it
+would be about an inch in depth. At the level of the sea the air reaches
+its greatest density. Two miles above sea-level it is only two-thirds as
+dense. On the tops of high mountains, four or five miles above sea
+level, the air is so rarefied as to cause the blood to start from the
+nostrils and eyelids of explorers. The walls of the little blood-vessels
+are broken by the expansion of the air that is inside. At the sea-level
+air presses at the rate of fifteen pounds per square foot in all
+directions. As one ascends to higher levels, the air pressure becomes
+less and less.</p>
+
+<p>The barometer is the instrument by which the pressure of air is
+measured. A glass tube, closed at one end, and filled with mercury, the
+liquid metal often called quicksilver, is inverted in a cup of the same
+metal, and so supported that the metal is free to flow between the two
+vessels. The pressure of air on the surface of the mercury in the cup is
+sufficient<span class='pagenum'><a name="Page_37" id="Page_37">[Pg 37]</a></span> at the sea-level to sustain a column of mercury thirty
+inches high in the tube. As the instrument is carried up the side of a
+mountain the mercury falls in the tube. This is because the air pressure
+decreases the higher up we go. If we should descend into the shaft of
+the deepest mine that reaches below the sea level, the column of air
+supported by the mercury in the cup would be a mile higher, and for this
+reason its weight would be correspondingly greater. The mercury would
+thus be forced higher in the tube than the thirty-inch mark, which
+indicates sea-level.</p>
+
+<p>Another form of barometer often seen is a tube, the lower and open end
+of which forms a U-shaped curve. In this open end the downward pressure
+of the air rests upon the mercury and holds it up in the closed end,
+forcing it higher as the instrument is carried to loftier altitudes. At
+sea level a change of 900 feet in altitude makes a change of an inch in
+the height of the mercury in the column. The glass tube is marked with
+the fractions of inches, or of the metre if the metric system of
+measurements is used.</p>
+
+<p>It is a peculiarity of air to become heated when it is compressed, and
+cooled when it is allowed to expand again. It is also true that when the
+sun rises, the atmosphere is warmed by its rays. This is why the hottest
+part of the day is near noon when the sun's rays fall vertically. The
+earth absorbs a great deal of the sun's heat in the daytime and through<span class='pagenum'><a name="Page_38" id="Page_38">[Pg 38]</a></span>
+the summer season. When it cools this heat is given off, thus warming
+the surrounding atmosphere. In the polar regions, north and south, the
+air is far below freezing point the year round. In the region of the
+Equator it rarely falls below 90 degrees, a temperature which we find
+very uncomfortable, especially when there is a good deal of moisture in
+the air.</p>
+
+<p>If we climb a mountain in Mexico, we leave the sultry valley, where the
+heat is almost unbearable, and very soon notice a change. For every
+three hundred feet of altitude we gain there is a fall of one degree in
+the temperature. Before we are half way up the slope we have left behind
+the tropical vegetation, and come into a temperate zone, where the
+plants are entirely different from those in the lower valley. As we
+climb, the vegetation becomes stunted, and the thermometer drops still
+lower. At last we come to the region of perpetual snow, where the
+climate is like that of the frozen north.</p>
+
+<p>So we see that the air becomes gradually colder as we go north or south
+from the Equator, and the same change is met as we rise higher and
+higher from the level of the sea.</p>
+
+<p>It is only when air is in motion that we can feel and hear it, and there
+are very few moments of the day, and days of the year, when there is not
+a breeze. On a still day fanning sets the air in motion, and creates a
+miniature breeze, the sound of which we hear in the swishing of the fan.
+The great blanket of air that covers the earth is in a state of almost
+constant<span class='pagenum'><a name="Page_39" id="Page_39">[Pg 39]</a></span> disturbance, because of the lightness of warm air and the
+heaviness of cold air. These two different bodies are constantly
+changing places. For instance, the heated air at the Equator is
+constantly being crowded upward by cold air which settles to the level
+of the earth. Cold streams of air flow to the Tropics from north and
+south of the Equator, and push upward the air heated by the sun.</p>
+
+<p>This constant inrush of air from north and south forms a double belt of
+constant winds. If the earth stood still, no doubt the direction would
+be due north and due south for these winds; but the earth rotates
+rapidly from west to east upon its axis, carrying with it everything
+that is securely fastened to the surface: the trees, the houses, etc.
+But the air is not a part of the earth, not even so much as the seas,
+the waters of which must stay in their proper basins, and be whirled
+around with other fixed objects. The earth whirls so rapidly that the
+winds from north and south of the Equator lag behind, and thus take a
+constantly diagonal direction. Instead of due south the northern belt of
+cold air drifts south-west and the southern belt drifts northwest. These
+are called the Trade Winds. Near the Equator they are practically east
+winds.</p>
+
+<p>The belt of trade winds is about fifty degrees wide. It swings northward
+in our summer and southward in our winter, its centre following the
+vertical position of the sun. Near the centre of the course which marks
+the meeting of the northern with the southern<span class='pagenum'><a name="Page_40" id="Page_40">[Pg 40]</a></span> winds is a "Belt of
+Calms" where the air draws upward in a strong draught. The colder air of
+the trade winds is pushing up the columns of light, heated air. This
+strip is known by sailors as "the Doldrums," or "the region of
+equatorial calms." Though never wider than two or three hundred miles,
+this is a region dreaded by captains of sailing-vessels, for they often
+lie becalmed for weeks in an effort to reach the friendly trade winds
+that help them to their desired ports. Vessels becalmed are at the mercy
+of sudden tempests which come suddenly like thunder-storms, and
+sometimes do great damage to vessels because they take the sailors
+unawares and allow no time to shorten sail.</p>
+
+<p>Until late years the routes of vessels were charted so that sailors
+could take advantage of the trade winds in their long voyages. It was
+necessary in the days of sailing-vessels for the captain to understand
+the movements of winds which furnished the motive power that carried his
+vessel. Fortunate it was for him that there were steady winds in the
+temperate zones that he could take advantage of in latitudes north of
+the Tropic of Cancer and south of the Tropic of Capricorn. What becomes
+of the hot air that rises in a constant stream above the "Doldrums,"
+pushed up by the cooler trade winds that blow in from north and south?
+Naturally this air cannot ascend very high, for it soon reaches an
+altitude in which its heat is rapidly lost, and it<span class='pagenum'><a name="Page_41" id="Page_41">[Pg 41]</a></span> would sink if it
+were not constantly being pushed by the rising column of warm air under
+it. So it turns and flows north and south at a level above the trade
+winds. Not far north of the Tropic of Cancer it sinks to the level of
+sea and land, and forms a belt of winds that blows ships in a
+northeasterly direction. Between trades and anti-trades is another zone
+of calms,&mdash;near the Tropics of Cancer and of Capricorn.</p>
+
+<p>The land masses of the continents with their high mountain ranges
+interfere with these winds, especially in the northern hemisphere, but
+in the Southern Pacific and on the opposite side of the globe the
+"Roaring Forties," as these prevailing westerly winds are known by the
+sailors, have an almost unbroken waste of seas over which they blow. In
+the long voyages between England and Australia, and in the Indian trade,
+the ships of England set their sails to catch the roaring forties both
+going and coming. They accomplish this by sailing past the Cape of Good
+Hope on the outward voyage and coming home by way of Cape Horn, thus
+circling the globe with every trip. In the North Atlantic, traffic is
+now mostly carried on in vessels driven by engines, not by sails. Yet
+the westerly winds that blow from the West Indies diagonally across the
+Atlantic are still useful to all sailing craft that are making for
+British ports.</p>
+
+<p>From the north and from the south cold air flows down into the regions
+of warmer climate. These<span class='pagenum'><a name="Page_42" id="Page_42">[Pg 42]</a></span> polar winds are not so important to sea
+commerce, but they do a great work in tempering the heat in the
+equatorial regions. We cannot know how much our summers are tempered by
+the cool breath of winds that blow over polar ice-fields. And the cold
+regions of the earth, in their brief summer, enjoy the benefits of the
+warm breezes that flow north and south from the heated equatorial
+regions.</p>
+
+<p>The land, north and south, is made habitable by the clouds. They gather
+their burdens of vapour from the warm seas, the wind drifts them north
+and south, where they let it fall in rains that make and keep the earth
+green and beautiful. From the clouds the earth gathers, like a great
+sponge, the water that stores the springs and feeds rivers and lakes.
+How necessary are the winds that transport the cloud masses!</p>
+
+<p>The air is the breath of life to all living things on our planet. Mars
+is one of the sun's family so provided. Plants or animals could probably
+live on the planet Mars. Do we think often enough of this invisible,
+life-giving element upon which we depend so constantly?</p>
+
+<p>The open air which the wind purifies by keeping it in motion is the best
+place in which to work, to play, and to sleep, when work and play are
+done and we rest until another day comes. Indoors we need all the air we
+can coax to come in through windows and doors. Fresh air purifies air
+that is<span class='pagenum'><a name="Page_43" id="Page_43">[Pg 43]</a></span> stale and unwholesome from being shut up. Nobody is afraid,
+nowadays, to breathe night air! What a foolish notion it was that led
+people to close their bedroom windows at night. Clean air, in plenty,
+day and night, we need. Air and sunshine are the two best gifts of God.<span class='pagenum'><a name="Page_44" id="Page_44">[Pg 44]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_WORK_OF_THE_WIND" id="THE_WORK_OF_THE_WIND"></a>THE WORK OF THE WIND</h2>
+
+
+<p>When the March wind comes blustering down the street, rudely dashing a
+cloud of dust in our faces, we are uncomfortable and out of patience. We
+duck our heads and cover our faces, but even then we are likely to get a
+cinder in one eye, to swallow germs by the dozens, and to get a gray
+coating of plain, harmless dust. We welcome the rain that lays the dust,
+or its feeble imitation, the water sprinkler, that brings us temporary
+relief.</p>
+
+<p>On the quietest day, even after a thorough sweeping and dusting of the
+library, you are able to write your name plainly on the film of dust
+that lies on the polished table. Take a book from the open shelves, and
+blow into the trough of its top. This is always dusty. Where does the
+dust come from? This is the house-keeper's riddle.</p>
+
+<p>The answer is not a hard one. I look out of my window on a street which
+is famous as the road Washington took on his retreat from White Plains
+to Trenton. It has always been the main thoroughfare between New York
+and Philadelphia, and now is the route that automobiles follow. A
+constant procession of vehicles passes my house, and to-day each one
+approaches in a cloud of dust. The air is gray with suspended particles
+of dirt. The wind carries the successive clouds, and they roll up
+against the houses like breakers on the beach. Windows and doors are
+loose enough to let dust sift in. When a door opens, the cloud enters
+and lights on rugs and carpets and curtains. Any ledge collects its
+share of dust. The beating of carpets and rugs disturbs the accumulated
+dust of many months.</p>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus044_th.jpg" width="500" height="314" alt="In this lonely Arizona desert the wind drifts the sand
+into dunes, just as it does on the toe of Cape Cod" title="" />
+<span class="caption">In this lonely Arizona desert the wind drifts the sand
+into dunes, just as it does on the toe of Cape Cod</span>
+</div>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus045_th.jpg" width="500" height="305" alt="The Grand Canyon of the Colorado shows on a magnificent
+scale the work of water in cutting away rock walls" title="" />
+<span class="caption">The Grand Canyon of the Colorado shows on a magnificent
+scale the work of water in cutting away rock walls</span>
+</div><p><span class='pagenum'><a name="Page_45" id="Page_45">[Pg 45]</a></span></p>
+
+<p>The wind sweeps the ploughed field, and takes all the dust it can carry.
+It blows the finest top soil from our gardens into the street. It blows
+soil from other fields and gardens into ours, so the level of our land
+is not noticeably lowered. The wind strips the high land and drops its
+burden on lower levels. This is one of the big jobs the water has to do,
+and the wind is a valuable helper. To tear down the mountains and fill
+in the valleys is the great work of the two partners, wind and water.</p>
+
+<p>Dead, still air holds the finest dust, without letting it fall. The
+buoyancy of the particles overcomes their weight. We see them in a
+sunbeam, like shining points of precious metal, and watch them. A light
+breeze picks up bits of soil and litter, from the smallest up to a
+certain size and weight. If the velocity of the wind increases, its
+carrying power increases. It is able to carry bits that are larger<span class='pagenum'><a name="Page_46" id="Page_46">[Pg 46]</a></span> and
+heavier. The following table is exact and interesting:</p>
+
+
+<div class='center'>
+<table border="0" cellpadding="4" cellspacing="10" summary="">
+<tr><td align='left'></td><td align='center'><i>Velocity in Miles per Hour</i></td><td align='center'><i>Pressure in Pounds per Sq. Ft.</i></td></tr>
+<tr><td align='left'>Light breeze</td><td align='center'>14</td><td align='center'>1</td></tr>
+<tr><td align='left'>Strong breeze</td><td align='center'>42</td><td align='center'>9</td></tr>
+<tr><td align='left'>Strong gale</td><td align='center'>70</td><td align='center'>25</td></tr>
+<tr><td align='left'>Hurricane</td><td align='center'>84</td><td align='center'>36</td></tr>
+</table></div>
+
+<p>The terrible paths of hurricanes are seen in forest countries. The trees
+are uprooted, as if a great roller had crushed them, throwing the tops
+all in one direction, and leaving the roots uncovered, and a sunken
+pocket where each tree stood. On a steep, rocky slope, the uprooting of
+scattered trees often loosens tons of rock, and sends the mass
+thundering down the mountain-side. Much more destruction may be
+accomplished by one brief tornado than by years of wear by ordinary
+breezes.</p>
+
+<p>The wind does much to help the waves in their patient beating on rocky
+shores. If the wind blows from the ocean and the tide is landward, the
+two forces combine, and the loose rocks are thrown against the solid
+beach with astonishing force. Even the gravel and the sharp sand are
+tools of great usefulness to the waves in grinding down the resisting
+shore. Up and back they are swept by the water, and going and coming
+they have their chance to scratch or strike a blow. Boulders on the
+beach become pockmarked by the constant sand-blast that plays upon them.
+The lower windows of exposed<span class='pagenum'><a name="Page_47" id="Page_47">[Pg 47]</a></span> seaside houses are dimmed by the sand that
+picks away the smooth surface outside, making it ground glass by the
+same process used in the factory. Lighthouses have this difficulty in
+keeping their windows clear. The "lantern" itself is sometimes reached
+by the sand grains. That is the cupola in which burns the great light
+that warns vessels away from the rocks and tells the captain where he
+is.</p>
+
+<p>In the Far Western States the telegraph poles and fence posts are soon
+cut off at the ground by the flinty knives the wind carries. These are
+the grains of sand that are blown along just above the ground. The trees
+are killed by having their bark girdled in this way. The sand-storms
+which in the orange and lemon region of California are called "Santa
+Anas" sometimes last two or three days, and damage the trees by piercing
+the tender bark with the needle-pointed sand.</p>
+
+<p>Wind-driven soil, gathered from the sides of bare hills and mountains,
+fills many valleys of China with a fine, hard-packed material called
+"loess." In some places it is hundreds of feet deep. The people dig into
+the side of a hill of this loess and carry out the diggings, making
+themselves homes, of many rooms, with windows, doors, and solid walls
+and floors, all in one solid piece, like the chambered house a mole
+makes underground in the middle of a field. So compact is the loess that
+there is no danger of a cave-in.</p>
+
+<p>The hills of sand piled up on the southern shore<span class='pagenum'><a name="Page_48" id="Page_48">[Pg 48]</a></span> of Lake Michigan, and
+at Provincetown, at the toe of Cape Cod, are the work of the wind. On
+almost any sandy shore these "dunes" are common. The long slope is
+toward the beach that furnishes the sand. The wind does the building. Up
+the slope it climbs, then drops its burden, which slides to the bottom
+of an abrupt landward steep. There is a gradual movement inland if the
+strongest winds come from the water. The shifting of the dunes threatens
+to cover fertile land near them. In the desert regions, the border-land
+is always in danger of being taken back again, even though it has been
+reclaimed from the desert and cultivated for long years.</p>
+
+<p>Besides tearing down, carrying away, and building up again the fragments
+of the earth's crust, the wind does much that makes the earth a pleasant
+planet to live on. It drives the clouds over the land, bringing rains
+and snows and scattering them where they will bless the thirsty ground
+and feed the springs and brooks and rivers. It scatters the seeds of
+plants, and thus plants forests and prairies and lovely mountain slopes,
+making the wonderful wild gardens that men find when they first enter
+and explore a new region. The trade winds blow the warm air of the
+Tropics north and south, making the climate of the northern countries
+milder than it would otherwise be. Sea winds blow coolness over the land
+in summer, and cool lake breezes temper the inland regions. From the
+snow-capped mountains<span class='pagenum'><a name="Page_49" id="Page_49">[Pg 49]</a></span> come the winds that refresh the hot, tired worker
+in the valleys.</p>
+
+<p>Everywhere the wind blows, the life-giving oxygen is carried. This is
+what we mean when we speak of fresh air. Stagnant air is as unwholesome
+as stagnant water. Constant moving purifies both. So we must give the
+wind credit for some of the greatest blessings that come into our lives.
+Light and warmth come from the sun. Pure water and pure air are gifts
+the bountiful earth provides. Without them there would be no life on the
+earth.<span class='pagenum'><a name="Page_50" id="Page_50">[Pg 50]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="RAIN_IN_SUMMER" id="RAIN_IN_SUMMER"></a>RAIN IN SUMMER</h2>
+
+
+<div class="poem"><div class="stanza">
+<span class="i0">How beautiful is the rain!<br /></span>
+<span class="i0">After the dust and heat,<br /></span>
+<span class="i0">In the broad and fiery street,<br /></span>
+<span class="i0">In the narrow lane,<br /></span>
+<span class="i0">How beautiful is the rain!<br /></span>
+</div><div class="stanza">
+<span class="i0">How it clatters along roofs,<br /></span>
+<span class="i0">Like the tramp of hoofs!<br /></span>
+<span class="i0">How it gushes and struggles out<br /></span>
+<span class="i0">From the throat of the overflowing spout!<br /></span>
+<span class="i0">Across the window-pane<br /></span>
+</div><div class="stanza">
+<span class="i0">It pours and pours;<br /></span>
+<span class="i0">And swift and wide,<br /></span>
+<span class="i0">With a muddy tide,<br /></span>
+<span class="i0">Like a river down the gutter roars<br /></span>
+<span class="i0">The rain, the welcome rain!<br /></span>
+</div><div class="stanza">
+<span class="i0">The sick man from his chamber looks<br /></span>
+<span class="i0">At the twisted brooks;<br /></span>
+<span class="i0">He can feel the cool<br /></span>
+<span class="i0">Breath of each little pool;<br /></span>
+<span class="i0">His fevered brain<br /></span>
+<span class="i0">Grows calm again,<br /></span>
+<span class="i0">And he breathes a blessing on the rain.<br /></span>
+</div><div class="stanza">
+<span class="i10">&mdash;H<small>ENRY</small> W. L<small>ONGFELLOW</small>.<br /></span>
+<span class='pagenum'><a name="Page_51" id="Page_51">[Pg 51]</a></span></div></div>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="WHAT_BECOMES_OF_THE_RAIN" id="WHAT_BECOMES_OF_THE_RAIN"></a>WHAT BECOMES OF THE RAIN?</h2>
+
+
+<p>The clouds that sail overhead are made of watery vapour. Sometimes they
+look like great masses of cotton-wool against the intense blue of the
+sky. Sometimes they are set like fleecy plumes high above the earth.
+Sometimes they hang like a sullen blanket of gray smoke, so low they
+almost touch the roofs of the houses. Indeed, they often rest on the
+ground and then we walk through a dense fog.</p>
+
+<p>In their various forms, clouds are like wet sponges, and when they are
+wrung dry they disappear&mdash;all their moisture falls upon the earth. When
+the air is warm, the water comes in the form of rain. If it is cold, the
+drops are frozen into hail, sleet, or snow.</p>
+
+<p>All of the water in the oceans, in the lakes and rivers, great and
+small, all over the earth, comes from one source, the clouds. In the
+course of a year enough rain and snow fall to cover the entire surface
+of the globe to a depth of forty inches. This quantity of water amounts
+to 34,480 barrels on every acre. What becomes of it all?</p>
+
+<p>We can easily understand that all the seas and the other bodies of water
+would simply add forty inches to their depth, and many would become
+larger,<span class='pagenum'><a name="Page_52" id="Page_52">[Pg 52]</a></span> because the water would creep up on their gradually sloping
+shores. We have to account for the rain and the snow that fall upon the
+dry land and disappear.</p>
+
+<p>Go out after a drenching rainstorm and look for the answer to this
+question. The gullies along the street are full of muddy, running water.
+There are pools of standing water on level places, but on every slope
+the water is hurrying away. The ground is so sticky that wagons on
+country roads may mire to the hubs in the pasty earth. There is no use
+in trying to work in the garden or to mow the lawn. The sod is soft as a
+cushion, and the garden soil is water-soaked below the depth of a
+spading-fork.</p>
+
+<p>The sun comes out, warm and bright, and the flagstones of the sidewalk
+soon begin to steam like the wooden planks of the board walk. The sun is
+changing the surface water into steam which rises into the sky to form a
+part of another bank of clouds. The earth has soaked up quantities of
+the water that fell. If we followed the racing currents in the gullies
+we should find them pouring into sewer mains at various points, and from
+these underground pipes the water is conducted to some outlet like a
+river. All of the streams are swollen by the hundreds of brooks and
+rivulets that are carrying the surface water to the lowest level.</p>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus052_th.jpg" width="500" height="305" alt="Rain and wind are the sculptors that have carved these
+strange castles out of a rocky table" title="" />
+<span class="caption">Rain and wind are the sculptors that have carved these
+strange castles out of a rocky table</span>
+</div>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus053_th.jpg" width="500" height="305" alt="All the water in the seas, lakes, rivers, and springs
+came out of the clouds" title="" />
+<span class="caption">All the water in the seas, lakes, rivers, and springs
+came out of the clouds</span>
+</div>
+
+<p><span class='pagenum'><a name="Page_53" id="Page_53">[Pg 53]</a></span></p>
+
+<p>So we can see some of the rainfall going back to the sky, some running
+off through rivulets to the sea, and some soaking into the ground. It
+will be interesting to follow this last portion as it gradually settles
+into the earth. The soil will hold a certain quantity, for it is made up
+of fine particles, all separated by air spaces, and it acts like a
+sponge. In seasons of drought and great heat the sun will draw this soil
+water back to the surface, by forming cracks in the earth, and fine,
+hair-like tubes, through which the vapour may easily rise. The gardener
+has to rake the surface of the beds frequently to stop up these channels
+by which the sun is stealing the precious moisture.</p>
+
+<p>The water that the surface soil cannot absorb sinks lower and lower into
+the ground. It finds no trouble to settle through layers of sand, for
+the particles do not fit closely together. It may come to a bed of clay
+which is far closer. Here progress is retarded. The water may
+accumulate, but finally it will get through, if the clay is not too
+closely packed. Again it may sink rapidly through thick beds of gravel
+or sand. Reaching another bed of clay which is stiffer by reason of the
+weight of the earth above it, the water may find that it cannot soak
+through. The only way to pass this clay barrier is to fill the basin,
+and to trickle over the edge, unless a place is found in the bottom
+where some looser substance offers a passage. Let us suppose that a
+concave clay basin of considerable depth is filled with water-soaked
+sand. At the very lowest point on the edge of this basin a stream will
+slowly trickle out, and will continue to flow, as long as water from
+above keeps the bowl full.<span class='pagenum'><a name="Page_54" id="Page_54">[Pg 54]</a></span></p>
+
+<p>It is not uncommon to find on hillsides, in many regions, little brooks
+whose beginnings are traceable to springs that gush out of the ground.
+The spring fills a little basin, the overflow of which is the brook. If
+the source of this spring could be traced underground, we might easily
+follow it along some loose rock formation until we come to a clay basin
+like the one described above. We might have to go down quite a distance
+and then up again to reach the level of this supply, but the level of
+the water at the mouth of the spring can never be higher than the level
+of the water in the underground supply basin.</p>
+
+<p>Often in hot summers springs "go dry." The level of water in the supply
+basin has fallen below the level of the spring. We must wait until
+rainfall has added to the depth of water in the basin before we can
+expect any flow into the pool which marks the place where the brook
+begins.</p>
+
+<p>Suppose we had no beds of clay, but only sand and gravel under the
+surface soil. We should then expect the water to sink through this loose
+material without hindrance, and, finding its way out of the ground, to
+flow directly into the various branches of the main river system of our
+region. After a long rain we should have the streams flooded for a few
+days, then dry weather and the streams all low, many of them entirely
+dry until the next rainstorm.</p>
+
+<p>Instead of this, the soil to a great depth is stored with water which
+cannot get away, except by the<span class='pagenum'><a name="Page_55" id="Page_55">[Pg 55]</a></span> slow process by which the springs draw
+it off. This explains the steady flow of rivers. What should we do for
+wells if it were not for the water basins that lie below the surface? A
+shallow well may go dry. Its owner digs deeper, and strikes a lower
+"vein" of water that gives a more generous supply. In the regions of the
+country where the drift soil, left by the great ice-sheet, lies deepest,
+the glacial boulder clay is very far down. The surface water, settling
+from one level to another, finally reaches the bottom of the drift.
+Wells have to be deep that reach this water bed.</p>
+
+<p>The water follows the slope of this bed and is drained into the ocean,
+sometimes by subterranean channels, because the bed of the nearest river
+is on a much higher level. So we must not think that the springs contain
+only the water that feeds the rivers. They contain more.</p>
+
+<p>The layers of clay at different levels, from the surface down to the
+bottom of the drift, form water basins and make it possible for people
+to obtain a water supply without the expense of digging deep wells. The
+clayey subsoil, only a few feet below the surface, checks the downward
+course of the water, so that the sun can gradually draw it back, and
+keep a supply where plant roots can get it. The vapour rising keeps the
+air humid, and furnishes the dew that keeps all plant life comfortable
+and happy even through the hot summer months.</p>
+
+<p>Under the drift lie layers of stratified rock, and<span class='pagenum'><a name="Page_56" id="Page_56">[Pg 56]</a></span> under these are the
+granites and other fire-formed rocks, the beginning of those rock masses
+which form the solid bulk of the globe. We know little about the core of
+the earth, but the granites that are exposed in mountain ridges are
+found to have a great capacity for absorbing water, so it is not
+unlikely that much surface water soaks into the rock foundations and is
+never drained away into the sea.</p>
+
+<p>The water in our wells is often hard. It becomes so by passing through
+strata of soil and rock made, in part, at least, of limestone, which is
+readily dissolved by water which contains some acid. Soil water absorbs
+acids from the decaying vegetation,&mdash;the dead leaves and roots of
+plants. Rain water is soft, and so is the water in ponds that have muddy
+basins, destitute of lime. Water in the springs and wells of the
+Mid-Western States is "hard" because it percolates through limestone
+material. In many parts of this country the well water is "soft,"
+because of the scarcity of limestone in the soil.</p>
+
+<p>I have seen springs around which the plants and the pebbles were coated
+with an incrustation of lime. "Petrified moss" is the name given to the
+plants thus turned to stone. The reason for this deposit is clear.
+Underground water is often subjected to great pressure, and at this time
+it is able to dissolve much more of any mineral substance than under
+ordinary conditions. When the pressure is released, the water is unable
+to hold in<span class='pagenum'><a name="Page_57" id="Page_57">[Pg 57]</a></span> solution the quantity of mineral it contains; therefore, as
+it flows out through the mouth of the spring, the burden of mineral is
+laid down. The plants coated with the lime gradually decay, but their
+forms are preserved.</p>
+
+<p>There are springs the water of which comes out burdened with iron, which
+is deposited as a yellowish or red mineral on objects over which it
+flows. Ponds fed by these springs accumulate deposits of the mineral in
+the muddy bottoms. Some of the most valuable deposits of iron ore have
+accumulated in bogs fed by iron-impregnated spring water. In a similar
+way lime deposits called marl or chalk are made.<span class='pagenum'><a name="Page_58" id="Page_58">[Pg 58]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_SOIL_IN_FIELDS_AND_GARDENS" id="THE_SOIL_IN_FIELDS_AND_GARDENS"></a>THE SOIL IN FIELDS AND GARDENS</h2>
+
+
+<p>City and country teachers are expected to teach classes about the
+formation and cultivation of soil. It is surprising how much of the
+needed materials can be brought in by the children, even in the cities.
+The beginning is a flowering plant growing in a pot. A window box is a
+small garden. A garden plot is a miniature farm.</p>
+
+<p><i>Materials to collect for study indoors.</i> A few pieces of different
+kinds of rock: Granite, sandstone, slate; gravelly fragments of each,
+and finer sand. Pebbles from brooks and seashore. Samples of clays of
+different colors, and sands. Samples of sandy and clay soils, black pond
+muck, peat and coal. Rock fossils. A box of moist earth with earthworms
+in it. <i>Keep it moist.</i> A piece of sod, and a red clover plant with the
+soil clinging to its roots.</p>
+
+<p><i>What is soil?</i> It is the surface layer of the earth's crust, sometimes
+too shallow on the rocks to plough, sometimes much deeper. Under deep
+soil lies the "subsoil," usually hard and rarely ploughed.</p>
+
+<p><i>What is soil made of?</i> Ground rock materials and decayed remains of
+animal and plant life. By slow decay the soil becomes rich food for the
+growing<span class='pagenum'><a name="Page_59" id="Page_59">[Pg 59]</a></span> of new plants. Wild land grows up to weeds and finally to
+forests. The soil in fields and gardens is cultivated to make it
+fertile. Plants take fertility from the soil. To maintain the same
+richness, plant food must be put back into the soil. This is done by
+deep tillage, and by mixing in with the soil manures, green crops, like
+clover, and commercial fertilizers.</p>
+
+<p><i>Plants must be made comfortable, and must be fed.</i> Few plants are
+comfortable in sand. It gets hot, it lets water through, and it shifts
+in wind and is a poor anchor for roots. Clay is so stiff that water
+cannot easily permeate it; roots have the same trouble to penetrate it
+and get at the food it is rich in. Air cannot get in.</p>
+
+<p>Sand mixed with clay makes a mellow soil, which lets water and air pass
+freely through. The roots are more comfortable, and the tiny root hairs
+can reach the particles of both kinds of mineral food. But the needful
+third element is decaying plant and animal substances, called "humus."
+These enrich the soil, but they do a more important thing: their decay
+hastens the release of plant food from the earthy part of the soil, and
+they add to it a sticky element which has a wonderful power to attract
+and hold the water that soaks into the earth.</p>
+
+<p><i>What is the best garden soil?</i> A mixture of sand, clay, and humus is
+called "loam." If sand predominates, it is a sandy loam&mdash;warm, mellow
+soil. If clay predominates, we have a clay loam&mdash;a<span class='pagenum'><a name="Page_60" id="Page_60">[Pg 60]</a></span> heavy, rich, but
+cool soil. All gradations between the two extremes are suited to the
+needs of crops, from the melons on sandy soil, to celery that prefers
+deep, cool soil, and cranberries that demand muck&mdash;just old humus.</p>
+
+<p><i>How do plant roots feed in soil?</i> By means of delicate root hairs which
+come into contact with particles of soil around which a film of soil
+water clings. This fluid dissolves the food, and the root absorbs the
+fluid. Plants can take no food in solid form. Hence it is of the
+greatest importance to have the soil pulverized and spongy, able to
+absorb and hold the greatest amount of water. The moisture-coated soil
+particles must have air-spaces between them. Air is as necessary to the
+roots as to the tops of growing plants.</p>
+
+<p><i>Why does the farmer plough and harrow and roll the land?</i> To pulverize
+the soil; to mellow and lighten it; to mix in thoroughly the manure he
+has spread on it, and to reach, if he can, the deeper layers that have
+plant food which the roots of his crops have not yet touched. Killing
+weeds is but a minor business, compared with tillage.</p>
+
+<p>Later, ploughing or cultivating the surface lightly not only destroys
+the weeds, but it checks the loss of water by evaporation from the
+cracks that form in dry weather. Raking the garden once a day in dry
+weather does more good than watering it. The "dust mulch" acts as a cool
+sunguard over the roots.<span class='pagenum'><a name="Page_61" id="Page_61">[Pg 61]</a></span></p>
+
+<p><i>The process of soil-making.</i> If the man chopping wood in the Yosemite
+Valley looks about him he can see the soil-making forces at work on a
+grand scale. The bald, steep front of El Capitan is of the hardest
+granite, but it is slowly crumbling, and its fragments are accumulating
+at the bottom of the long slope. Rain and snow fill all crevices in the
+rocks. Frost is a wonderful force in widening these cracks, for water
+expands when it freezes. The loosened rock masses plough their way down
+the steep, gathering, as they go, increasing power to tear away any
+rocks in their path.</p>
+
+<p>Wind blows finer rock fragments along, and they lodge in cracks. Fine
+dust and the seeds of plants are lodged there. The rocky slopes of the
+Yosemite Valley are all more or less covered with trees and shrubs that
+have come from wind-sown seeds. These plants thrust their roots deeper
+each year into the rock crevices. The feeding tips of roots secrete
+acids that eat away lime and other substances that occur in rocks. Dead
+leaves and other discarded portions of the trees rot about their roots,
+and form soil of increasing depth. The largest trees grow on the rocky
+soil deposited at the base of the slope. The tree's roots prevent the
+river from carrying it off.</p>
+
+<p>When granite crumbles, its different mineral elements are separated.
+Clear, glassy particles of quartz we call sand. Dark particles of
+feldspar become clay, and may harden into slate. Sand may become
+sandstone. Exposed slate and sandstone<span class='pagenum'><a name="Page_62" id="Page_62">[Pg 62]</a></span> are crumbled by exposure to wind
+and frost and moving water, and are deposited again as sand-bars and
+beds of clay.</p>
+
+<p>The most interesting phase of soil study is the discovery of what a work
+the humble earthworm does in mellowing and enriching the soil.<span class='pagenum'><a name="Page_63" id="Page_63">[Pg 63]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_WORK_OF_EARTHWORMS" id="THE_WORK_OF_EARTHWORMS"></a>THE WORK OF EARTHWORMS</h2>
+
+
+<p>The farmer and the gardener should expect very poor crops if they
+planted seed without first ploughing or spading the soil. Next, its fine
+particles must be separated by the breaking of the hard clods. A wise
+man ploughs heavy soil in the fall. It is caked into great clods which
+crumble before planting time. The water in the clods freezes in winter.
+The expansion due to freezing makes this soil water a force that
+separates the fine particles. So the frost works for the farmer.</p>
+
+<p>Just under the surface of the soil lives a host of workers which are our
+patient friends. They work for their living, and are perhaps unconscious
+of the fact that they are constantly increasing the fertility of the
+soil. They are the earthworms, also called fishworms, which are
+distributed all over the world. They are not generally known to farmers
+and gardeners as friendly, useful creatures, and their services are
+rarely noticed. We see robins pulling them out of the ground, and we are
+likely to think the birds are ridding us of a garden pest. What we need
+is to use our eyes, and to read the wonderful discoveries recorded in a
+book called<span class='pagenum'><a name="Page_64" id="Page_64">[Pg 64]</a></span> "Vegetable Mould and Earthworms," written by Charles
+Darwin.</p>
+
+<p>The benefits of ploughing and spading are the loosening and pulverizing
+of the packed earth; the mixing of dead leaves and other vegetation on
+and near the surface with the more solid earth farther down; the letting
+in of water and air; and the checking of loss of water through cracks
+the sun forms by baking the soil dry.</p>
+
+<p>The earthworm is a creature of the dark. It cannot see, but it is
+sufficiently sensitive to light to avoid the sun, the rays of which
+would shrivel up its moist skin. Having no lungs or gills, the worm uses
+the skin as the breathing organ; and it must be kept moist in order to
+serve its important use. This is why earthworms are never seen above
+ground except on rainy days, and never in the top soil if it has become
+dry. In seasons of little rain, they go down where the earth is moist,
+and venture to the surface only at night, when dew makes their coming up
+possible.</p>
+
+<p>Earthworms have no teeth, but they have a long snout that protrudes
+beyond the mouth. Their food is found on and in the surface soil. They
+will eat scraps of meat by sucking the juices, and scrape off the pulp
+of leaves and root vegetables in much the same way. Much of their
+subsistence is upon organic matter that can be extracted from the soil.
+Quantities of earth are swallowed. It is rare that an earthworm is dug
+up that does not show earth<span class='pagenum'><a name="Page_65" id="Page_65">[Pg 65]</a></span> pellets somewhere on their way through the
+long digestive canal. The rich juices of plant substance are absorbed
+from these pellets as they pass through the body.</p>
+
+<p>Earthworms explore the surface of the soil by night, and pick up what
+they can find of fresh food. Nowhere have I heard of them as a nuisance
+in gardens, but they eagerly feed on bits of meat, especially fat, and
+on fresh leaves. They drag all such victuals into their burrows, and
+begin the digestion of the food by pouring on it from their mouths a
+secretion somewhat like pancreatic juice.</p>
+
+<p>The worms honeycomb the earth with their burrows, which are long,
+winding tubes. In dry or cold weather these burrows may reach eight feet
+under ground. They run obliquely, as a rule, from the surface, and are
+lined with a layer of the smooth soil, like soft paste, cast from the
+body. The lining being spread, the burrow fits the worm's body closely.
+This enables it to pass quickly from one end to the other, though it
+must wriggle backward or forward without turning around.</p>
+
+<p>At the lower end of the burrow, an enlarged chamber is found, where
+hibernating worms coil and sleep together in winter. At the top, a
+lining of dead leaves extends downward for a few inches, and in day time
+a plug of the same material is the outside door. At night the worm comes
+to the surface, and casts out the pellets of earth swallowed. The burrow
+grows in length by the amount of earth<span class='pagenum'><a name="Page_66" id="Page_66">[Pg 66]</a></span> scraped off by the long snout
+and swallowed. The daily amount of excavation done is fairly estimated
+by the castings observed each morning on the surface.</p>
+
+<p>One earthworm's work for the farmer is not very much, but consider how
+many are at work, and what each one is doing. It is boring holes through
+the solid earth, and letting in the surface water and the air. It is
+carrying the lower soil up to the surface, often the stubborn subsoil,
+that no plough could reach. It is burying and thus hastening the decay
+of plant fibre, which lightens heavy soil and makes it rich because it
+is porous. Moreover, the earthworms are doing over and over again this
+work of fining and turning over the soil, which the plough does but
+seldom.</p>
+
+<p>By the continuous carrying up of their castings, the earthworms
+gradually bury manures spread on the surface. The collapse of their
+burrows and the making of new ones keep the soil constantly in motion.
+The particles are being loosened and brought into contact with the soil
+water, that dissolves, and thus frees for the use of feeding roots, the
+plant food stored in the rock particles that compose the mineral part of
+the soil.</p>
+
+<p>The weight of earth brought to the surface by worms in the course of a
+year has been carefully estimated. Darwin gives seven to eighteen tons
+per acre as the lowest and highest reports, based on careful collecting
+of castings by four observers,<span class='pagenum'><a name="Page_67" id="Page_67">[Pg 67]</a></span> working on small areas of totally
+different soils. In England, earthworms have done a great deal more
+toward burying boulders and ancient ruins than any other agency. They
+eagerly burrow under heavy objects, the weight of which causes them to
+crush the honeycombed earth. Undiscouraged, the earthworms repeat their
+work.</p>
+
+<p>"Long before man existed, the land was regularly ploughed, and continues
+still to be ploughed by earthworms. It may be doubted whether there are
+many other animals which have played so important a part in the history
+of the world as have these lowly organized creatures."</p>
+
+<p>After years of study, Charles Darwin came to this conclusion. The more
+we study the lives of these earth-consuming creatures, the more fully do
+we believe what the great nature student said. The fertile soil is made
+of rock meal and decayed leaves and roots. Only recently have ploughs
+been invented. But the great forest crops have grown in soil made mellow
+by the earthworm's ploughing.<span class='pagenum'><a name="Page_68" id="Page_68">[Pg 68]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="QUIET_FORCES_THAT_DESTROY_ROCKS" id="QUIET_FORCES_THAT_DESTROY_ROCKS"></a>QUIET FORCES THAT DESTROY ROCKS</h2>
+
+
+<p>Wind and water are the blustering active agents we see at work tearing
+down rocks and carrying away their particles. They do the most of this
+work of levelling the land; but there are quiet forces at work which
+might not attract our attention at all, and yet, without their help,
+wind and running water would not accomplish half the work for which they
+take the credit.</p>
+
+<p>The air contains certain destructive gases which by their chemical
+action separate the particles of the hardest rocks, causing them to
+crumble. Now the wind blows away these crumbling particles, and the
+solid unchanged rock beneath is again exposed to the crumbling agencies.</p>
+
+<p>The changes in temperature between day and night cause rocks to contract
+and expand, and these changes put a strain upon the mineral particles
+that compose them. Much scaling of rock surfaces is due to these causes.
+Building a fire on top of a rock, and then dashing water upon the heated
+mass, shatters it in many directions. This process merely intensifies
+the effect produced by the mild changes of winter and summer. Water is
+present in most rocks, in surprising quantities,<span class='pagenum'><a name="Page_69" id="Page_69">[Pg 69]</a></span> often filling the
+spaces in porous rocks like sandstones.</p>
+
+<p>When winter brings the temperature down to the freezing point, the water
+near the surface of the rock first feels it. Ice forms, and every
+particle of water is swollen by the change. A strain is put upon the
+mineral particles against which the particles of ice crowd for more
+room. Frost is a very powerful agent in the crumbling of rocks, as well
+as of stubborn clods of earth. In warm climates, and in desert regions
+where there is little moisture in the rocks, this destructive action of
+freezing water is not known. In cold countries, and in high altitudes,
+where the air is heavy with moisture, its greatest work is done.</p>
+
+<p>Some kinds of rock decay when they become dry, and resist crumbling
+better when they absorb a certain amount of moisture. Alternate wetting
+and drying is destructive to certain rocks.</p>
+
+<p>One of the unnoticed agents of rock decay is the action of lowly plants.
+Mosses grow upon the faces of rocks, thrusting their tiny root processes
+into pits they dig deeper by means of acids secreted by the delicate
+tips. You have seen shaded green patches of lichens, like little rugs,
+of different shapes, spread on the surface of rocks. But you cannot see
+so well the work these growths are doing in etching away the surface,
+and feeding upon the decaying mineral substance.</p>
+
+<p>Mosses and lichens do a mighty work, with the<span class='pagenum'><a name="Page_70" id="Page_70">[Pg 70]</a></span> help of water, in
+reducing rocks to their original elements, and thus forming soil. No
+plants but lichens and mosses can grow on the bare faces of rocks. As
+their root-like processes lengthen and go deeper into the rock face,
+particles are pried off, and the under-substance is attacked. Higher
+plants then find a footing. Have you not seen little trees growing on a
+patch of moss which gets its food from the air and the rock to which it
+clings? The spongy moss cushion soaks up the rain and holds it against
+the rock face. A streak of iron in the rock may cause the water to
+follow and rust it out, leaving a distinct crevice. Now the roots of any
+plant that happens to be growing on the moss may find a foot-hold in the
+crack. Streaks of lime in a rock readily absorb water, which gradually
+dissolves and absorbs its particles, inviting the roots to enter these
+new passages and feed upon the disintegrating minerals. Dead leaves
+decay, and the acids the trickling water absorbs from them are
+especially active in disintegrating lime rocks.</p>
+
+<p>From such small beginnings has resulted the shattering of great rock
+masses by the growth of plants upon them. Tree roots that grow in rock
+crevices exert a power that is irresistible. The roots of smaller plants
+do the same great work in a quieter way.</p>
+
+<p>When a hurricane or a flood tears down the mountain-side, sweeping
+everything before it, trees, torn out by the roots, drag great masses
+of<span class='pagenum'><a name="Page_71" id="Page_71">[Pg 71]</a></span> rock and soil into the air, and fling them down the slope. Wind and
+water thus finish the destruction which the humble mosses and lichens
+began. What seemed an impregnable fortress of granite has crumbled into
+fragments. Its particles are reduced to dust, or are on the way to this
+condition. The plant food locked up in granite boulders becomes
+available to hungry roots. Forests, grain-fields, and meadows cover the
+work of destructive agencies with a mantle of green.<span class='pagenum'><a name="Page_72" id="Page_72">[Pg 72]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="HOW_ROCKS_ARE_MADE" id="HOW_ROCKS_ARE_MADE"></a>HOW ROCKS ARE MADE</h2>
+
+
+<p>The granite shaft is made out of the original substance of the earth's
+crust. Its minerals are the elements out of which all of the rock masses
+of the earth are formed, no matter how different they look from granite.
+Sandstone is made of particles of quartz. Clay and slate are made out of
+feldspar and mica. Iron ore comes from the hornblende in granite. The
+mineral particles, reassembled in different proportions, form all of the
+different rocks that are known.</p>
+
+<p>Here in my hand is a piece of pudding-stone. It is made of pebbles of
+different sizes, each made of different coloured minerals. The pebbles
+are cemented together with a paste that has hardened into stone. This
+kind of rock the geologists call <i>conglomerate</i>. Pudding-stone is the
+common name, for the pebbles in the pasty matrix certainly do suggest
+the currants and the raisins that are sprinkled through a Christmas
+pudding.</p>
+
+<p>Under the seashores there are forming to-day thick beds of sand. The
+rivers bring the rock material down from the hills, and it is sorted and
+laid down. The moving water drops the heaviest particles near shore, and
+carries the finer ones farther out before letting them fall.</p>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus072_th.jpg" width="500" height="311" alt="The town of Cripple Creek, Colorado, which has grown up
+like magic since 1891, covers the richest gold and silver mines in the
+world" title="" />
+<span class="caption">The town of Cripple Creek, Colorado, which has grown up
+like magic since 1891, covers the richest gold and silver mines in the
+world</span>
+</div>
+
+<div class="figcenter" style="width: 355px;">
+<img src="images/illus073_th.jpg" width="355" height="500" alt="The level valley is filled up with fine rock flour washed
+from the sides of the neighboring mountains" title="" />
+<span class="caption">The level valley is filled up with fine rock flour washed
+from the sides of the neighboring mountains</span>
+</div>
+
+<p><span class='pagenum'><a name="Page_73" id="Page_73">[Pg 73]</a></span></p>
+
+<p>The hard water, that comes through limestone rocks, adds lime in
+solution to the ocean water. All the shellfish of the sea, and the
+creatures with bony skeletons, take in the bone-building, shell-making
+lime with their food. Generations of these inhabitants of the sea have
+died, and their shells and bones have accumulated and been transformed
+into thick beds of limestone on the ocean floor. This is going on
+to-day; but the limestone does not accumulate as rapidly as when the
+ocean teemed with shell-bearing creatures of gigantic size. Of these we
+shall speak in another chapter.</p>
+
+<p>The fine dust that is blown into the ocean from the land, and that makes
+river water muddy, accumulates on the sea bottom as banks of mud, which
+by the burden of later deposits is converted into clay. Sandstone is but
+the compressed sand-bank.</p>
+
+<p>In the study of mountains, geologists have discovered that old seashores
+were thrown up into the first great ridges that form the backbone of a
+mountain system. The Rocky Mountains, and the Appalachian system on the
+east, were made out of thick strata of rocks that had been formed by
+accumulations of mud and sand&mdash;the washings of the land&mdash;on the opposite
+shores of a great mid-continental sea, that stretched from the crest of
+one great mountain system across to the other, and north and south from
+the Laurentian Hills to the<span class='pagenum'><a name="Page_74" id="Page_74">[Pg 74]</a></span> Gulf of Mexico. The great weight of the
+accumulating layers of rock materials on one side, and the wasted land
+surfaces on the other, made the sea border a line of greatest weakness
+in the crust of the earth. The shrinking of the globe underneath caused
+the break; mashing and folding followed, throwing the ridge above
+sea-level, and making dry land out of rock waste which had been
+accumulating, perhaps for millions of years, under the sea. The
+wrinkling of the earth's crust was the result of crushing forces which
+produced tremendous heat.</p>
+
+<p>Streams of lava sprang out through the fissures and poured streams of
+melted rock down the sides of the fold, quite burying, in many places,
+the layers of limestone, sandstone, and clay. Between the strata of
+water-formed rocks there were often created chimney-like openings, into
+which molten rock from below was forced, forming, when cool, veins and
+dikes of rock material, specimens of the substance of the earth's
+interior.</p>
+
+<p>Tremendous pressure and heat, acting upon stratified rocks saturated
+with water transform them into very different kinds of rock. Limestone,
+subjected to these forces, is changed into marble. Clays are transformed
+into slates. Sandstone is changed into quartzite, the sand grains being
+melted so as to become no longer visible to the naked eye. The
+anthracite coal of the Pennsylvania mountains is the result of heat and
+pressure acting upon soft coal. Associated with<span class='pagenum'><a name="Page_75" id="Page_75">[Pg 75]</a></span> these beds of hard coal
+are beds of black lead, or graphite, the substance used in making "lead"
+pencils. We believe that the same forces that operated to transform clay
+rocks into slate, and limestone into marble, transformed soft coal into
+hard, and hard coal into graphite, in the days when the earth was young.</p>
+
+<p>The word <i>sedimentary</i> is applied to rocks which were originally laid
+down under water, as sediment, brought by running water, or by wind, or
+by the decay of organic substances. <i>Stratified</i> rocks are those which
+are arranged in layers. Sedimentary rocks will fall into this class.
+<i>Aqueous</i> rocks are those which are formed under water. Most of the
+stratified and sedimentary rocks, but not all, may be included under
+this term. Rocks that are made out of fragments of other rocks torn down
+by the agencies of erosion are called <i>fragmental</i>. Wind, water, and ice
+are the three great agencies that wear away the land, bring rock
+fragments long distances, and deposit them where aqueous rocks are being
+formed. Volcanic eruptions bring material from the earth's interior.
+This material ranges all the way from huge boulders to the finest
+impalpable dust, called volcanic ashes. Rivers of ice called glaciers
+crowd against their banks, loosening rock masses and carrying away
+fragments of all sizes, in their progress down the valley. Brooks and
+rivers carry the pebbles and the larger rock masses they are able to
+loosen from their walls and<span class='pagenum'><a name="Page_76" id="Page_76">[Pg 76]</a></span> beds, and grind them smooth as they move
+along toward lower levels.</p>
+
+<p>The air itself causes rocks to crumble; percolating water robs them of
+their soluble salts, reducing even solid granite to a loose mass of
+quartz grains and clay. Plants and animals absorb as food the mineral
+substances of rocks, when they are dissolved in water. They transform
+these food elements into their own body substance, and finally give back
+their dead bodies, the mineral substances of which are freed by decay to
+return to the earth, and become elements of rock again.</p>
+
+<p>The decay of rock is well shown by the materials that accumulate at the
+base of a cliff. Angular fragments of all sizes, but all more or less
+flattened, come from strata of shaly rock, that can be seen jutting out
+far above. A great deal of this sort of material is found mingled with
+the soil of the Northeastern States. Round pebbles in pudding-stone have
+been formed in brook beds and deposited on beaches where they have
+become caked in mud and finally consolidated into rock. If the beach
+chanced to be sandy instead of muddy, a matrix of sandy paste holds the
+larger pebbles in place. Limestone paste cements together the pebbles of
+limestone conglomerates.</p>
+
+<p>In St. Augustine many of the houses are built of coquina rock, a mass of
+broken shells which have become cemented together by lime mud, derived
+from their own decay. On the slopes of volcanoes,<span class='pagenum'><a name="Page_77" id="Page_77">[Pg 77]</a></span> rock fragments of all
+kinds are cemented together by the flowing lava. So we see that there
+are pudding-stones of many kinds to be found. If some solvent acid is
+present in the water that percolates through these rocks it may soften
+the cement and thus free the pebbles, reducing the conglomerate again to
+a mere heap of shell fragments, or gravel, or rounded pebbles.</p>
+
+<p>The story of rock formation tells how fire and water, and the two
+combined, have made, and made over, again and again, the substance of
+the earth's crust. Chemical and physical changes constantly tear down
+some portions of the earth to build up others. The constant, combined
+effort of wind and water is to level the earth and fill up the ocean
+bed. Rocks are constantly being formed; the changes that have been going
+on since the world began are still in progress. We can see them all
+about us on any and every day of our lives.<span class='pagenum'><a name="Page_78" id="Page_78">[Pg 78]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="GETTING_ACQUAINTED_WITH_A_RIVER" id="GETTING_ACQUAINTED_WITH_A_RIVER"></a>GETTING ACQUAINTED WITH A RIVER</h2>
+
+
+<p>I have two friends whose childhood was spent in a home on the banks of a
+noble eastern river. Their father taught the boy and the girl to row a
+boat, and later each learned the more difficult art of managing a canoe.
+On holidays they enjoyed no pleasure so much as a picnic on the
+river-bank at some point that could be reached by rowing. As they grew
+older, longer trips were planned, and the river was explored as far as
+it was navigable by boat or canoe. Last summer when vacation came, these
+two carried out a long-cherished plan to find the beginning of the
+river&mdash;to follow it to its source. So they left home, and canoed
+up-stream, until the stream became a brook, so shallow they could go no
+farther. Then they followed it on foot&mdash;wading, climbing, making little
+d&eacute;tours, but never losing the little river. At last they came to the
+beginning of it&mdash;a tiny rivulet trickled out of the side of a hill,
+filling a wooden keg that formed a basin, where thirsty passers-by could
+stoop and drink. They decided to mark the spring, so that people who
+found it later, and were refreshed by its clear water, might know that
+here was born the greatest river of a great state. But they were not the
+original<span class='pagenum'><a name="Page_79" id="Page_79">[Pg 79]</a></span> discoverers. Above the spring, a board was nailed to a tree,
+saying that this is the headwater of the river with the beautiful Indian
+name, Susquehanna.</p>
+
+<p>It was a dry summer, and the overflow of the basin was almost all drunk
+up by the thirsty ground. They could scarcely follow it, except by the
+groove cut by the rivulet in seasons when the flow was greater. They
+followed the runaway brook, through the grass roots, that almost hid it.
+As the ground grew steeper, it hurried faster. Soon it gathered the
+water of other springs, which hurried toward it in small rivulets,
+because its level was lower. Water always seeks the lowest level it can
+find. Sometimes marshy spots were reached where water stood in the holes
+made by the feet of cattle that came there to drink. The water was
+muddy, and seemed to stand still. But it was settling steadily, and at
+one side the little river was found, flowing away with the water it drew
+from the swampy, springy ground. All the mud was gone, now; the water
+was clear. It flowed in a bed with a stony floor, and there were rough
+steps where the water fell down in little sheets, forming a waterfall,
+the first of many that make this river beautiful in the upper half of
+its course. To get from the high level of that hillside spring to the
+low level of the sea, the water has to make a fall of twenty-three
+hundred feet, but it makes the descent gradually. It could not climb
+over anything, but always found a way to get around the rocks and<span class='pagenum'><a name="Page_80" id="Page_80">[Pg 80]</a></span> hills
+that stood in its way. When the flat marsh land interfered, the water
+poured in and overflowed the basin at the lowest margin.</p>
+
+<p>In the rocky ground the two explorers found that the stream had widened
+its channel by entering a narrow crevice and wearing away its walls. The
+continual washing of the water wears away stone. Rocks are softened by
+being wet. Streaks of iron in the hardest granite will rust out and let
+the water in. Then the lime in rocks is easily dissolved. Every dead
+leaf the river carried along added an acid to the water, and this made
+easier the process of dissolving the limestone.</p>
+
+<p>Every crumbling rock gives the river tools that it uses like hammer and
+chisel and sandpaper to smooth all the uneven surfaces in its bed, to
+move stumbling blocks, and to dig the bed deeper and wider. The steeper
+the slope is, the faster the stream flows, and the larger the rocks it
+can carry. Rocks loosened from the stream bed are rolled along by the
+current. Then bang! against the rocks that are not loose, and often they
+are able to break them loose. The fine sand is swept along, and its
+sharp points strike like steel needles, and do a great work in polishing
+roughness and loosening small particles from the stream bed. The bigger
+pebbles of the stream have banged against the rock walls, with the same
+effect, smoothing away unevenness and pounding fragments loose, rolling
+against one another, and getting their own rough corners worn away.<span class='pagenum'><a name="Page_81" id="Page_81">[Pg 81]</a></span></p>
+
+<p>The makers of stone marbles learned their business from a brook. They
+cut the stone into cubical blocks, and throw them into troughs, into
+which is poured a stream of running water. The blocks are kept in
+motion, and the grinding makes each block help the rest to grind off the
+eight corners and the twelve ridges of each one. The water becomes muddy
+with the fine particles, just as the drip from a grindstone becomes
+unclean when an axe is ground. Pretty soon all the blocks in the trough
+are changed into globes&mdash;the marbles that children buy at the shops when
+marble season comes around.</p>
+
+<p>I suppose if the troughs are not watched and emptied in time, the
+marbles would gradually be ground down to the size of peas, then to the
+size of small bird shot, and finally they would escape as muddy water
+and fine sand grains.</p>
+
+<p>Sure it is that the sandy shores that line most rivers are the remnants
+of hard rocks that have been torn out and ground up by the action of the
+current.</p>
+
+<p>Not very many miles from its first waterfall the stream had grown so
+large that my two friends knew that they would soon find their canoes.
+The plan now was to float down the curious, winding river and to learn,
+if the river and the banks could tell them, just why the course was so
+crooked on the map. They came into a broad, level valley where streams
+met them, coming out of deep clefts between the hills they were leaving
+behind them. The banks were pebbly, but blackened with slimy mud<span class='pagenum'><a name="Page_82" id="Page_82">[Pg 82]</a></span> that
+made the water murky. The current swerved from one side to the other,
+sometimes quite close to the bank, where the river turned and formed a
+deep bend. On this side the bank was steep, the roots of plants and
+trees exposed. On the opposite side a muddy bank sloped gently out into
+the stream. Here building up was going on, to offset the tearing down.</p>
+
+<p>The sharp bends are made sharper, once the current is deflected from the
+middle of the stream to one side. At length the loops bend on each other
+and come so near together that the current breaks through, leaving a
+semicircular bayou of still water, and the river's course straightened
+at that place. It must have been in a spring flood that this cut-off was
+made, and, the break once made was easily widened, for the soil is fine
+mud which, when soaked, crumbles and dissolves into muddy water.</p>
+
+<p>Stately and slow that river moves down to the bay, into which it empties
+its load. The rain that falls on hundreds of square miles of territory
+flows into the streams that feed this trunk. The little spring that is
+the headwater of the system is but one of many pockets in the hillsides
+that hold the water that soaks into the ground and give it out by slow
+degrees. Surface water after a rain flows quickly into the streams. It
+is the springs that hold back their supply and keep the rivers from
+running dry in hot weather.<span class='pagenum'><a name="Page_83" id="Page_83">[Pg 83]</a></span></p>
+
+<p>Do they feel now that they know their river? Are they ready to leave it,
+and explore some other? Indeed, no. They are barely introduced to it.
+All kinds of rivers are shown by the different parts of this one. It is
+a river of the mountains and of the lowland. It flows through woods and
+prairies, through rocky passes and reedy flats. It races impetuously in
+its youth, and plods sedately in later life. The trees and the other
+plants that shadow this stream, and live by its bounty, are very
+different in the upland and in the lowland. The scenery along this
+stream shows endless variety. Up yonder all is wild. Down here great
+bridges span the flood, boats of all kinds carry on the commerce between
+two neighbour cities. A great park comes down to the river-bank on one
+side. Canoes are thick as they can paddle on late summer afternoons.</p>
+
+<p>No one can ever really know a river well enough to feel that it is an
+old story. There is always something new it has to tell its friends. So
+my two explorers say, and they know far more about their friendly river
+than I do.<span class='pagenum'><a name="Page_84" id="Page_84">[Pg 84]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_WAYS_OF_RIVERS" id="THE_WAYS_OF_RIVERS"></a>THE WAYS OF RIVERS</h2>
+
+
+<p>A canal is an artificial river, built to carry boats from one place to
+another. Its course is, as nearly as possible, a straight line between
+two points. A river, we all agree, is more beautiful than a canal, for
+it winds in graceful curves, in and out among the hills, its waters
+seeking the lowest level, always.</p>
+
+<p>No artist could lay out curves more beautiful than the river forms.
+These curves change from year to year, some slowly, some more rapidly.
+It is not hard to understand just why these changes take place.</p>
+
+<p>Some rivers are dangerous for boating at certain points. The current is
+strong, and there are eddies and whirlpools that have to be avoided, or
+the boat becomes unmanageable. People are drowned each season by
+trusting themselves to rivers the dangerous tricks of which they do not
+know. Deep holes are washed out of the bed of the stream by whirling
+eddies. The pot-holes of which people talk are deep, rounded cavities,
+ground out of the rocky stream-bed by the scouring of sand and loose
+stones driven by whirling eddies in shallow basins. Every year deepens
+each pot-hole until some change in the stream-bed shifts the eddy to
+another place.<span class='pagenum'><a name="Page_85" id="Page_85">[Pg 85]</a></span></p>
+
+<p>No stream finds its channel ready-made; it makes its own, and constantly
+changes it. The current swings to one side of the channel, lifting the
+loose sediment and grinding deeper the bed of the stream. The water lags
+on the opposite side, and sediment falls to the bottom. So the
+building-up of one side is going on at the same time that the
+tearing-down process is being carried on on the other. With the lowering
+of the bed the river swerves toward one bank, and a hollow is worn by
+slow degrees. The current swings into this hollow, and in passing out is
+thrown across the stream to the opposite bank. Here its force wears away
+another hollow; and so it zigzags down-stream. The deeper the hollows,
+the more curved becomes the course, if the general fall is but moderate.
+It is toward the lower courses of the stream that the winding becomes
+more noticeable. The sediment that is carried is deposited at the point
+where the current is least strong, so that while the outcurves become
+sharper by the tearing away of the stream's bank, the incurves become
+sharper by the building up of this bank.</p>
+
+<p>The Mississippi below Memphis is thrown into a wonderful series of
+curves by the erosion and the deposit caused by the current zigzagging
+back and forth from one bank to the other. Gradually the curves become
+loops. The river's current finally jumps across the meeting of the
+curves, and abandons the circular bend. It becomes a bayou or lagoon of
+still water, while the current flows on in the straightened<span class='pagenum'><a name="Page_86" id="Page_86">[Pg 86]</a></span> channel.
+All rivers that flow through flat, swampy land show these intricate
+winding channels and many lagoons that have once been curves of the
+river.</p>
+
+<p>No one would ever mistake a river for a lake or any other body of water,
+yet rivers differ greatly in character. One tears its way along down its
+steep, rock-encumbered channel between walls that rise as vertical
+precipices on both sides. The roaming, angry waters are drawn into
+whirlpools in one place. They lie stagnant as if sulking in another,
+then leap boisterously over ledges of rock and are churned into creamy
+foam at the bottom. Outside the mountainous part of its course this same
+river flows broad and calm through a mud-banked channel, cut by
+tributary streams that draw in the water of low, sloping hills.</p>
+
+<p>The Missouri is such a wild mountain stream at its headwaters. We who
+have seen its muddy waters from Sioux City to St. Louis would hardly
+believe that its impetuous and picturesque youth could merge into an old
+age so comfortable and placid and commonplace.</p>
+
+<p>This thing is true of all rivers. They flow, gradually or suddenly, from
+higher to lower levels. To reach the lowest level as soon as possible is
+the end each river is striving toward. If it could, each river would cut
+its bed to this depth at the first stage of its course. Its tools are
+the rocks it carries, great and small. The force that uses these tools<span class='pagenum'><a name="Page_87" id="Page_87">[Pg 87]</a></span>
+is the power of falling water, represented by the current of the stream.
+The upper part of a river such as the Missouri or Mississippi engages in
+a campaign of widening and deepening its channel, and carrying away
+quantities of sediment. The lower reaches of the stream flow through
+more level country; the current is checked, and a vast burden of
+sediment is laid down. Instead of tearing away its banks and bottom, the
+river fills up gradually with mud. The current meanders between banks of
+sediment over a bottom which becomes shallower year by year. The Rocky
+Mountains are being carried to the Gulf of Mexico. The commerce of the
+river is impeded by mountain d&eacute;bris deposited as mud-banks along the
+river's lower course.</p>
+
+<p>Many rivers are quiet and commonplace throughout their length. They flow
+between low, rounded hills, and are joined by quiet streams, that occupy
+the separating grooves between the hills. This is the oldest type of
+river. It has done its work. Rainfall and stream-flow have brought the
+level of the land nearly to the level of the stream. Very little more is
+left to be ground down and carried away. The landscape is beautiful, but
+it is no longer picturesque. Wind and water have smoothed away
+unevennesses. Trees and grass and other vegetation check erosion, and
+the river has little to do but to carry away the surface water that
+falls as rain.</p>
+
+<p>But suppose our river, flowing gently between its grassy banks, should
+feel some mighty power lifting<span class='pagenum'><a name="Page_88" id="Page_88">[Pg 88]</a></span> it up, with all its neighbour hills and
+valleys, to form a wrinkle in the still unstable crust of the earth.
+Away off at the river's mouth the level may not have changed, or that
+region may have been depressed instead of elevated by the shrinking
+process. Suppose the great upheaval has not severed the upper from the
+lower courses of the stream. With tremendous force and speed, the
+current flows from the higher levels to the lower. The river in the
+highlands strikes hard to reach the level of its mouth. It grinds with
+all its might, and all its rocky tools, upon its bed. All the mud is
+scoured out, and then the underlying rocks are attacked. If these rocks
+are soft and easily worn away, the channel deepens rapidly. One after
+another the alternating layers are excavated, and the river flows in a
+canyon which deepens more and more. As the level is lowered, the current
+of the stream becomes slower and the cutting away of its bed less rapid.
+The stream is content to flow gently, for it has almost reached the old
+level, on which it flowed before the valley became a ridge or
+table-land.</p>
+
+<p>The rivers that flow in canyons have been thousands of years in carving
+out their channels, yet they are newer, geologically speaking, than the
+streams that drain the level prairie country. The earth has risen, and
+the canyons have been carved since the prairies became rolling, level
+ground.</p>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus088_th.jpg" width="500" height="310" alt="This little pond is a basin hollowed by the same glacier
+that scattered the stones and rounded the hills" title="" />
+<span class="caption">This little pond is a basin hollowed by the same glacier
+that scattered the stones and rounded the hills</span>
+</div>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus089_th.jpg" width="500" height="316" alt="Every stream is wearing away its banks, while trees and
+grass blades are holding on to the soil with all their roots" title="" />
+<span class="caption">Every stream is wearing away its banks, while trees and
+grass blades are holding on to the soil with all their roots</span>
+</div>
+
+<p><span class='pagenum'><a name="Page_89" id="Page_89">[Pg 89]</a></span></p>
+
+<p>The Colorado River flows through a canyon with walls that in places
+present sheer vertical faces a mile in depth, and so smooth that no
+trail can be found by which to reach from top to bottom. The region has
+but slight erosion by wind, and practically none by rain. The local
+rainfall is very slight. So the river is the one force that has acted to
+cut down the rocks, and its force is all expended in the narrow area of
+its own bed. Had frequent rains been the rule on the Colorado plateau,
+the angles of the mesas would have been rounded into hills of the
+familiar kind so constantly a part of the landscape in the eastern half
+of the continent.</p>
+
+<p>The Colorado is an ancient river which has to carry away the store of
+moisture that comes from the Pacific Ocean and falls as snow on the high
+peaks of the Rocky Mountains. Similar river gorges with similar stories
+to tell are the Arkansas, the Platte, and the Yellowstone. All cut their
+channels unaided through regions of little rain.</p>
+
+<p>When the earth's crust is thrown up in mountain folds, and between them
+valleys are formed, the level of rivers is sometimes lowered and the
+rapidity of their flow is checked. A stream which has torn down its
+walls at a rapid rate becomes a sluggish water-course, its current
+clogged with sediment, which it has no power to carry farther. When such
+a river begins to build and obstruct its own waters it bars its progress
+and may form a lake as the outlet of its tributary streams. Many ancient
+rivers have been utterly changed and some obliterated by general
+movements of the earth's crust.<span class='pagenum'><a name="Page_90" id="Page_90">[Pg 90]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_STORY_OF_A_POND" id="THE_STORY_OF_A_POND"></a>THE STORY OF A POND</h2>
+
+
+<p>Look out of the car window as you cross a flat stretch of new prairie
+country, and you see a great many little ponds of water dotting the
+green landscape. Forty years ago Iowa was a good place to see ponds of
+all shapes and sizes. The copious rainfall of the early spring gathered
+in the hollows of the land, and the stiff clay subsoil prevented the
+water from soaking quickly into the ground. The ponds might dry away
+during the hot, dry summer, leaving a baked clay basin, checked with an
+intricate system of cracks. Or if rains were frequent and heavy, they
+might keep full to the brim throughout the season.</p>
+
+<p>Tall bulrushes stood around the margins of the largest ponds, and
+water-lilies blossomed on the surface during the summer. The bass and
+the treble of the spring chorus were made by frogs and toads and little
+hylas, all of which resorted to the ponds to lay their eggs, in coiled
+ropes or spongy masses, according to their various family traditions. On
+many a spring night my zo&ouml;logy class and I have visited the squashy
+margins of these ponds, and, by the light of a lantern, seen singing
+toads and frogs sitting on bare hummocks of grass roots<span class='pagenum'><a name="Page_91" id="Page_91">[Pg 91]</a></span> that stood
+above the water-line. The throat of each musician was puffed out into a
+bag about the size and shape of a small hen's egg; and all were singing
+for dear life, and making a din that was almost ear-splitting at close
+range. So great was the self-absorption of these singers that we could
+approach them, daze them with the light of the lantern, and capture any
+number of them with our long-handled nets before they noticed us. But it
+was not easy to persuade them to sing in captivity, no matter how many
+of the comforts of home we provided in the school aquariums. So, after
+some very interesting nature studies, we always carried them back and
+liberated them, where they could rejoin their kinsfolk and neighbours.</p>
+
+<p>It was when we were scraping the mud from our rubber boots that we
+realized the character of the bottoms of our prairie ponds. The slimy
+black deposit was made partly of the clay bottom, but largely of
+decaying roots and tops of water plants of various kinds. Whenever it
+rained or the wind blew hard, the bottom was stirred enough to make the
+water muddy; and on the quietest days a pail of pond water had a tinge
+of brown because there were always decaying leaves and other rubbish to
+stain its purity.</p>
+
+<p>The farmers drained the ponds as fast as they were able, carrying the
+water, by open ditches first, and later by underground tile drains, to
+lower levels. Finally these trunk drain pipes discharged the water into
+streams or lakes. To-day a large proportion of<span class='pagenum'><a name="Page_92" id="Page_92">[Pg 92]</a></span> the pond areas of Iowa
+has disappeared; the hollow tile of terra-cotta has been the most
+efficient means of converting the waste land, covered by ponds, into
+fertile fields.</p>
+
+<p>But the ponds that have not been drained are smaller than they used to
+be, and are on the straight road to extinction. This process one can see
+at any time by visiting a pond. Every year a crop of reeds and a dozen
+other species of vigorous water plants dies at the top and adds the
+substance of their summer growth to the dust and other refuse that
+gathers in the bottom of the pond. Each spring roots and seeds send up
+another crop, if possible more vigorous than the last, and this top
+growth in turn dies and lies upon the bottom. The pond level varies with
+the rainfall of the years, but it averages a certain depth, from which
+something is each year subtracted by the accumulations of rotting
+vegetable matter in the bottom. Evaporation lowers the water-level,
+especially in hot, dry summers. From year to year the water plants draw
+in to form a smaller circle, the grassy meadow land encroaches on all
+sides. The end of the story is the filling up of the pond basin with the
+rotting substance of its own vegetation. This is what is happening to
+ponds and inland marshes by slow degrees. The tile drain pipes
+obliterate the pond in a single season. Nature is more deliberate. She
+may require a hundred years to fill up a single pond which the farmer
+can rid himself of by a few days of work and a few rods of tiling.<span class='pagenum'><a name="Page_93" id="Page_93">[Pg 93]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_RIDDLE_OF_THE_LOST_ROCKS" id="THE_RIDDLE_OF_THE_LOST_ROCKS"></a>THE RIDDLE OF THE LOST ROCKS</h2>
+
+
+<p>Outside of my window two robins are building a nest in the crotch of a
+blossoming red maple tree. And just across the hedge, men are digging a
+big square hole in the ground&mdash;the cellar of our neighbour's new house.
+It looks now as if the robins would get their house built first, for
+they need but one room, and they do not trouble about a cellar. I shall
+watch both houses as they grow through the breezy March days.</p>
+
+<p>The brown sod was first torn up by a plough, which uncovered the red New
+Jersey soil. Two men, with a team hitched to a scraper, have carried
+load after load of the loose earth to a heap on the back of the lot,
+while two other men with pickaxes dug into the hard subsoil, loosening
+it, so that the scraper could scoop it up.</p>
+
+<p>This subsoil is heavy, like clay, and it breaks apart into hard clods.
+At the surface the men found a network of tree roots, about which the
+soil easily crumbled. Often I hear a sharp, metallic stroke, unlike the
+dull sound of the picks striking into the earth. The digger has struck a
+stone, and he must work around it, pry it up and lift it out of the way.
+A row of these stones is seen at one side<span class='pagenum'><a name="Page_94" id="Page_94">[Pg 94]</a></span> of the cellar hole, ranged
+along the bank. They are all different in size and shape, and red with
+clay, so I can't tell what they are made of. But from this distance I
+see plainly that they are irregular in form and have no sharp corners.
+The soil strewn along the lot by the scraper is full of stones, mostly
+irregular, but some rounded; some are as big as your head, others grade
+down to the sizes of marbles.</p>
+
+<p>When I went down and examined this red earth, I found pebbles of all
+shapes and sizes, gravel in with the clay, and grains of sand. This
+rock-sprinkled soil in New Jersey is very much like soil which I know
+very well in Iowa; it looks different in colour, but those pebbles and
+rock fragments must be explained in the same way here as there.</p>
+
+<p>These are not native stones, the outcrop of near-by hillsides, but
+strangers in this region. The stones in Iowa soil are also imported.</p>
+
+<p>The prairie land of Iowa has not many big rocks on the surface, yet
+enough of them to make trouble. The man who was ploughing kept a sharp
+lookout, and swung his plough point away from a buried rock that showed
+above ground, lest it should break the steel blade. One of the farmer's
+jobs for the less busy season was to go out with sledge and dynamite
+sticks, and blast into fragments the buried boulders too large to move.
+Sometimes building a hot fire on the top of it, and throwing on water,<span class='pagenum'><a name="Page_95" id="Page_95">[Pg 95]</a></span>
+would crack the stubborn "dornick" into pieces small enough to be loaded
+on stone-boats.</p>
+
+<p>I remember when the last giant boulder whose buried bulk scarcely showed
+at the surface, was fractured by dynamite. Its total weight proved to be
+many tons. We hauled the pieces to the great stone pile which furnished
+materials for walling the sides of a deep well and for laying the
+foundation of the new house. Yet for years stones have been
+accumulating, all of them turned out of the same farm, when pastures and
+swampy land came under the plough.</p>
+
+<p>Draw a line on the map from New York to St. Louis, and then turn
+northward a little and extend it to the Yellowstone Park. The
+boulder-strewn states lie north of this line, and are not found south of
+it, anywhere. Canada has boulders just like those of our Northern
+States. The same power scattered them over all of the vast northern half
+of North America and a large part of Europe.</p>
+
+<p>What explanation is there for this extensive distribution of unsorted
+d&eacute;bris?<span class='pagenum'><a name="Page_96" id="Page_96">[Pg 96]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_QUESTION_ANSWERED" id="THE_QUESTION_ANSWERED"></a>THE QUESTION ANSWERED</h2>
+
+
+<p>The rocks tell their own story, partly, but not wholly. They told just
+enough to keep the early geologists guessing; and only very recently has
+the guessing come upon the truth.</p>
+
+<p>These things the rocks told:</p>
+
+<p>1. We have come from a distance.</p>
+
+<p>2. We have had our sharp corners worn off.</p>
+
+<p>3. Many of us have deep scratches on our sides.</p>
+
+<p>4. At various places we have been dumped in long ridges, mixed with much
+earth.</p>
+
+<p>5. A big boulder is often balanced on another one.</p>
+
+<p>The first thing the geologist noted was the fact that these boulders are
+strangers&mdash;that is, they are not the native rocks that outcrop on
+hillsides and on mountain slopes near where they are found. Far to the
+north are beds of rock from which this d&eacute;bris undoubtedly came. Could a
+flood have scattered them as they are found? No, for water sorts the
+rock d&eacute;bris it deposits, and it rounds and polishes rock fragments,
+instead of scratching and grooving them and leaving them angular, as
+these are.</p>
+
+<p>Professor Agassiz went to Switzerland and studied the glaciers. He found
+unsorted rock fragments<span class='pagenum'><a name="Page_97" id="Page_97">[Pg 97]</a></span> where the glacier's nose melted, and let them
+fall. They were worn and scratched and grooved, by being frozen into the
+ice, and dragged over the rocky bed of the stream. The rocky walls of
+the valley were scored by the glacier's tools. Rounded domes of rock
+jutted out of the ground, in the paths of the ice streams, just like the
+granite outcrop in Central Park in New York, and many others in the
+region of scattered boulders.</p>
+
+<p>After long studies in Europe and in North America, Professor Agassiz
+declared his belief that a great ice-sheet once covered the northern
+half of both countries, rounding the hills, scooping out the valleys and
+lake basins, and scattering the boulders, gravel, and clay, as it
+gradually melted away.</p>
+
+<p>The belief of Professor Agassiz was not accepted at once, but further
+studies prove that he guessed the riddle of the boulders. The rich soil
+of the Northern States is the glacial drift&mdash;the mixture of rock
+fragments of all sizes with fine boulder clay, left by the gradual
+melting of the great ice-sheet as it retreated northward at the end of
+the "Glacial Epoch."<span class='pagenum'><a name="Page_98" id="Page_98">[Pg 98]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="GLACIERS_AMONG_THE_ALPS" id="GLACIERS_AMONG_THE_ALPS"></a>GLACIERS AMONG THE ALPS</h2>
+
+
+<p>Switzerland is a little country without any seacoast, mountainous, with
+steep, lofty peaks, and narrow valleys. The climate is cool and moist,
+and snow falls the year round on the mountain slopes. A snow-cap covers
+the lower peaks and ridges. Above the level of nine thousand feet the
+bare peaks rise into a dry atmosphere; but below this altitude, and
+above the six thousand-foot mark, lies the belt of greatest snowfall.
+Peaks between six and nine thousand feet high are buried under the
+Alpine snow-field, which adds thickness with each storm, and is drained
+away to feed the rushing mountain streams in the lower valleys.</p>
+
+<p>The snow that falls on the steep, smooth slope clings at first; but as
+the thickness and the weight of these snow banks increase, their hold on
+the slope weakens. They may slip off, at any moment. The village at the
+foot of the slope is in danger of being buried under a snow-slide, which
+people call an avalanche. "Challanche" is another name for it. The
+hunter on the snow-clad mountains dares not shout for fear that his
+voice, re&euml;choing among the silent mountains, may start an avalanche on
+its deadly plunge into the valley.<span class='pagenum'><a name="Page_99" id="Page_99">[Pg 99]</a></span></p>
+
+<p>On the surface of the snow-field, light snow-flakes rest. Under them the
+snow is packed closer. Deeper down, the snow is granular, like pellets
+of ice; and still under this is ice, made of snow under pressure. The
+weight of the accumulated snow presses the underlying ice out into the
+valleys. These streams are the glaciers&mdash;rivers of ice.</p>
+
+<p>The glaciers of the Alps vary in length from five to fifteen miles, from
+one to three miles in width, and from two hundred to six hundred feet in
+thickness. They flow at the rate of from one to three feet a day, going
+faster on the steeper slopes.</p>
+
+<p>It is hard to believe that any substance as solid and brittle as ice can
+flow. Its movement is like that of stiff molasses, or wax, or pitch. The
+tremendous pressure of the snow-field pushes the mass of ice out into
+the valleys, and its own weight, combined with the constant pressure
+from behind, keeps it moving.</p>
+
+<p>The glacier's progress is hindered by the uneven walls and bed of the
+valley, and by any decrease in the slope of the bed. When a flat, broad
+area is reached, a lake of ice may be formed. These are not frequent in
+the Alps. The water near the banks and at the bottom of a river does not
+flow as swiftly as in the middle and at the surface of the stream. The
+flow of ice in a glacier is just so. Friction with the banks and bottom
+retards the ice while the middle parts go forward, melting under the
+strain, and freezing again. There is a constant readjusting<span class='pagenum'><a name="Page_100" id="Page_100">[Pg 100]</a></span> of
+particles, which does not affect the solidity of the mass.</p>
+
+<p>The ice moulds itself over any unevenness in its bed if it cannot remove
+the obstruction. The drop which would cause a small waterfall in a
+river, makes a bend in the thick body of the ice river. Great cracks,
+called <i>crevasses</i>, are made at the surface, along the line of the bend.
+The width of the V-shaped openings depends upon the depth of the glacier
+and the sharpness of the bend that causes the breaks.</p>
+
+<p>Rocky ridges in the bed of the ice-stream may cause crevasses that run
+lengthwise of the glacier. Snow may fill these chasms or bridge them
+over. The hunter or the tourist who ventures on the glacier is in
+constant danger, unless he sees solid ice under him. Men rope themselves
+together in climbing over perilous places, so that if one slips into a
+crevasse his mates can save him.</p>
+
+<p>A glacier tears away and carries away quantities of rock and earth that
+form the walls of its bed. As the valley narrows, tremendous pressure
+crowds the ice against the sides, tearing trees out by the roots and
+causing rock masses to fall on the top of the glacier, or to be dragged
+along frozen solidly into its sides. The weight of the ice bears on the
+bed of the glacier, and its progress crowds irresistibly against all
+loose rock material. The glacier's tools are the rocks it carries frozen
+into its icy walls and bottom. These rocks rub against the walls,<span class='pagenum'><a name="Page_101" id="Page_101">[Pg 101]</a></span>
+grinding off d&eacute;bris which is pushed or carried along. No matter how
+heavy the boulders are that fall in the way of the ice river, the ice
+carries them along. It cannot drop them as a river of water would do.
+Slowly they travel, and finally stop where the nose of the glacier melts
+and leaves all d&eacute;bris that the mountain stream, fed by the melting of
+the ice, cannot carry away.</p>
+
+<p>The bedrock under a glacier is scraped and ground and scored by the
+glacier's tools&mdash;the rock fragments frozen into the bottom of the ice.
+These rocks are worn away by constant grinding, just as a steel knife
+becomes thin and narrow by use. Scratches and scorings and polished
+surfaces are found in all rocks that pass one another in close contact.
+Its worn-out tools the glacier drops at the point where its ice melts.
+This great, unsorted mass of rock meal and coarser d&eacute;bris the stream is
+gradually scattering down the valley.</p>
+
+<p>The name "moraine" has been given to the earth rubbish a glacier
+collects and finally dumps. The <i>top moraine</i> is at the surface of the
+ice. The <i>lateral moraines</i>, one at each side, are the d&eacute;bris gathered
+from the sides of the valley. The <i>ground moraine</i> is what d&eacute;bris the
+ice pushes and drags along on the bottom. The <i>terminal moraine</i> is the
+dumping-ground of this mass of material, where the ice river melts.</p>
+
+<p>Glaciers, like other rivers, often have tributary streams. A <i>median
+moraine</i>, seen as a dark streak<span class='pagenum'><a name="Page_102" id="Page_102">[Pg 102]</a></span> running lengthwise on the surface of a
+glacier, means that two branch glaciers have united to form this one. Go
+back far enough and you will reach the place where the two streams come
+together. The two lateral moraines that join form the middle line of
+d&eacute;bris, the median moraine. Three ice-streams joined produce two top
+moraines. They locate the lateral moraines of the middle glacier.</p>
+
+<p>The surface of a glacier is often a mass of broken and rough ice,
+forming a series of pits and pinnacles that make crossing impossible.
+The sun melts the surface, forming pools and percolating streams of
+water, that honeycomb the mass. Underneath, the ice is tunnelled, and a
+rushing stream flows out under the end of the glacier. It is not clear,
+but black with mud, called <i>boulder clay</i>, or <i>till</i>, made of ground
+rock, and mixed with fragments of all shapes and sizes. This is the meal
+from the glacier's mill, dumped where the water can sift it.</p>
+
+<p>"Balanced rocks" are boulders, one upon another, that once lay on a
+glacier, and were left in this strange, unstable position when the
+supporting ice walls melted away from them. In Bronx Park in New York
+the "rocking stone" always attracts attention. The glacier that lodged
+it there, also rounded the granite dome in Central Park and scattered
+the rock-strewn boulder clay on Long Island. Doubtless in an earlier day
+the edges of this glacier were thrust out into the Atlantic, not far
+from the Great South Bay, and icebergs broke off and floated away.</p>
+
+<div class="figcenter" style="width: 397px;">
+<img src="images/illus102a_th.jpg" width="397" height="500" alt="Potsdam sandstone showing ripple marks" title="" />
+<span class="caption">Potsdam sandstone showing ripple marks</span>
+</div>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus102b_th.jpg" width="500" height="325" alt="By permission of the American Museum of Natural History
+
+Glacial stri&aelig; on Lower Helderberg limestone" title="" />
+<span class="caption">By permission of the American Museum of Natural History<br />
+Glacial stri&aelig; on Lower Helderberg limestone</span>
+</div>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus103a_th.jpg" width="500" height="397" alt="Glacial grooves in the South Meadow, Central Park, New
+York" title="" />
+<span class="caption">Glacial grooves in the South Meadow, Central Park, New
+York</span>
+</div>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus103b_th.jpg" width="500" height="397" alt="By permission of the American Museum of Natural History
+
+Mt. Tom, West 83d St., New York" title="" />
+<span class="caption">By permission of the American Museum of Natural History<br />
+Mt. Tom, West 83d St., New York</span>
+</div><p><span class='pagenum'><a name="Page_103" id="Page_103">[Pg 103]</a></span></p>
+
+<p>Glaciers are small to-day compared with what they were long ago, in
+Europe and in America. The climate became warmer, and the ice-cap
+retreated. Old moraines show that the ice rivers of the Alps once came
+much farther down the valleys than they do now. Smooth, deeply scored
+domes of rock, the one in Central Park and the bald head of Mount Tom,
+are just like those that lie in Alpine valleys from which the glaciers
+have long ago retreated. There are old moraines far up the sides of
+valleys, showing that once the glaciers were far deeper than now. No
+other power could have brought rocks from strata higher up the
+mountains, and lodged them thus.</p>
+
+<p>Nearer home, Mt. Shasta and Mt. Rainier still have glaciers that have
+dwindled in size, until they bear little comparison to the gigantic
+ice-streams that once filled the smooth beds their puny successors flow
+into. Remnants of glaciers lie in the hollows of the Sierras. We must go
+north to find the snow-fields of Alaska and glaciers worthy to be
+compared with those ancient ice rivers whose work is plainly to be seen,
+though they are gone.<span class='pagenum'><a name="Page_104" id="Page_104">[Pg 104]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_GREAT_ICE-SHEET" id="THE_GREAT_ICE-SHEET"></a>THE GREAT ICE-SHEET</h2>
+
+
+<p>Greenland is green only along its southern edge, and only in summer, so
+its name is misleading. It is a frozen continent lying under a great
+ice-cap, which covers 500,000 square miles and is several thousand feet
+in thickness. The top of this icy table-land rises from five thousand to
+ten thousand feet above the sea-level. The long, cold winters are marked
+by great snowfall, and the drifts do not have time to melt during the
+short summer; and so they keep getting deeper and deeper. Streams of ice
+flow down the steeps into the sea, and break off by their weight when
+they are pushed out into the water. These are the icebergs which float
+off into the North Atlantic, and are often seen by passengers on
+transatlantic steamers.</p>
+
+<p>Long ago Greenland better deserved its name. Explorers who have climbed
+the mountain steeps that guard the unknown ice-fields of the interior
+have discovered, a thousand feet above the sea-level, an ancient beach,
+strewn with shells of molluscs like those which now inhabit salt water,
+and skeletons of fishes lie buried in the sand. It is impossible to
+think that the ocean has subsided. The only explanation that accounts
+for the ancient<span class='pagenum'><a name="Page_105" id="Page_105">[Pg 105]</a></span> beach, high and dry on the side of Greenland's icy
+mountain is that the continent has been lifted a thousand feet above its
+former level. This is an accepted fact.</p>
+
+<p>We know that climate changes with changed altitude as well as latitude.
+Going up the side of a mountain, even in tropical regions, we may reach
+the snow-line in the middle of summer. Magnolia trees and tree ferns
+once grew luxuriantly in Greenland forests. Their fossil remains have
+been found in the rocks. This was long before the continent was lifted
+into the altitude of ice and snow. And it is believed that the climate
+of northern latitudes has become more severe than formerly from other
+causes. It is possible that the earth's orbit has gradually changed in
+form and position.</p>
+
+<p>If Greenland should ever subside until the ancient beach rests again at
+sea-level, the secrets of that unknown land would be revealed by the
+melting of the glacial sheet that overspreads it. Possibly it would turn
+out to be a mere flock of islands. We can only guess. North America had,
+not so long ago, two-thirds of its area covered with an ice-sheet like
+that of Greenland, and a climate as cold as Greenland's. At this time
+the land was lifted two to three thousand feet higher than its present
+level. All of the rain fell as snow, and the ice accumulated and became
+thicker year by year. Instead of glaciers filling the gorges, a great
+ice flood covered all the land, and pushed southward as far as the Ohio<span class='pagenum'><a name="Page_106" id="Page_106">[Pg 106]</a></span>
+River on the east and Yellowstone Park in the west. The Rocky Mountains
+and some parts of the Appalachian system accumulated snow and formed
+local glaciers, separated from the vast ice-sheet.</p>
+
+<p>The unstable crust of the earth began to sink at length, and gradually
+the ice-sheet's progress southward was checked, and it began to recede
+by melting. All along the borders of this great fan-shaped ice-field
+water accumulated from the melting, and flooded the streams which
+drained it to the Atlantic and the Gulf. Icebergs broken off of the edge
+of the retiring ice-sheet floated in a great inland sea. The land sank
+lower and lower until the general level was five hundred to one thousand
+feet lower than it now is. The climate became correspondingly warm, and
+the icebergs melted away. Then the land rose again, and in time the
+inland sea was drained away into the ocean, except for the waters that
+remained in thousands of lakes great and small that now occupy the
+region covered by the ice.</p>
+
+<p>Ancient sea beaches mark the level of high water at the time that the
+flood followed the melting ice. On the shores of Lake Champlain, but
+nearly five hundred feet higher than the present level of the lake,
+curious geologists have found many kinds of marine shells on a
+well-marked old sea beach. The members of one exploring party in the
+same region were surprised and delighted to come by digging upon the
+skeleton of a whale that had drifted ashore<span class='pagenum'><a name="Page_107" id="Page_107">[Pg 107]</a></span> in the ancient days when
+the inland sea joined the Atlantic.</p>
+
+<p>Lake Ontario's ancient beach is five hundred feet above the present
+water-level; Lake Erie's is two hundred fifty feet above it; Lake
+Superior's three hundred thirty feet higher than the present beach. No
+doubt when the water stood at the highest level, the Great Lakes formed
+one single sheet of water which settled to a lower level as the rivers
+flowing south cut their channels deep enough to draw off the water
+toward the Gulf. Lake Winnipeg is now the small remnant of a vast lake
+the shores of which have been traced. The Minnesota River finally made
+its way into the Mississippi and drained this great area the stranded
+beaches of which still remain. The name of Agassiz has been given to the
+ancient lake formed by the glacial flood and drained away thousands of
+years ago but not until it had built the terraced beach which locates it
+on the geological map of the region.</p>
+
+<p>When the ice-sheet came down from the north it dragged along all of the
+soil and loose rock material that lay in its path. With the boulders
+frozen into its lower surface it scratched and grooved the firm bedrock
+over which it slid, and rounded it to a smooth and billowy surface. The
+progress of the ice-sheet was southward, but it spread like a fan so
+that its widening border turned to east and west.</p>
+
+<p>When it reached its southernmost limit and began to melt, it laid down a
+great ridge of unsorted rock<span class='pagenum'><a name="Page_108" id="Page_108">[Pg 108]</a></span> material, remnants of which remain to this
+day,&mdash;the terminal moraine of the ancient ice-sheet. The line of this
+ancient deposit starts on Long Island, crosses New Jersey and
+Pennsylvania, then dips southward, following the general course of the
+Ohio River to its mouth, forming bluffs in southern Ohio, Indiana, and
+Illinois. The line bends upward as it crosses central Missouri, a corner
+of Kansas, and eastern Nebraska, parallel with the course of the
+Missouri.</p>
+
+<p>As the ice-sheet melted, boulders were dropped all over the Northern
+States and Canada. These were both angular and rounded. In some places
+they are scattered thickly over the surface and are so numerous as to be
+a great hindrance to agriculture. In many places great boulders of
+thousands of tons weight are perched on very slight foundations, just
+where they lodged when the ice went off and left them, after carrying
+them hundreds of miles. Around them are scattered quantities of loose
+rock material, not scored or ground as are those which were carried on
+the under-surface of the glacial ice. These unscarred fragments rode on
+the top of the ice. They were a part of the top moraine of the glacial
+sheet.</p>
+
+<p>The finest material deposited is rock meal, ground by the great glacial
+mill, and called "boulder clay." It is a stiff, dense, stony paste in
+which boulders of all sizes, gravel, pebbles, and cobblestones are
+cemented.<span class='pagenum'><a name="Page_109" id="Page_109">[Pg 109]</a></span></p>
+
+<p>The "drift" of the ice-sheet is the rubbish, coarse and fine, it left
+behind as it retreated. Below the Ohio River there is a deep soil
+produced by the decay of rocks that lie under it. North of Ohio is
+spread that peculiar mixture of earth and rock fragments which was
+transported from the north and spread over the land which the ice-sheet
+swept bare and ground smooth and polished.</p>
+
+<p>The drift has been washed away in places by the floods that followed the
+ice. Granite domes are thus exposed, the grooves and scratches of which
+tell in what direction the ice flood was travelling. Miles away from
+that scored granite, but in the same direction as the scratches,
+scattered fragments of the same foundation rock cover fields and
+meadows. Thus, much of the drift material can be traced to its original
+home, and the course of the ice-sheet can be determined. Many immense
+boulders the home of which was in the northern highlands of Canada rode
+southward, frozen into icebergs that floated in the great inland sea.
+Great quantities of d&eacute;bris were added to the original glacial drift
+through the agency of these floating ice masses, which melted by slow
+degrees.<span class='pagenum'><a name="Page_110" id="Page_110">[Pg 110]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="FOLLOWING_SOME_LOST_RIVERS" id="FOLLOWING_SOME_LOST_RIVERS"></a>FOLLOWING SOME LOST RIVERS</h2>
+
+
+<p>What would you think if the boat in which you were floating down a
+pleasant river should suddenly grate upon sand, and you should look over
+the gunwale and find that here the waters sank out of sight, the river
+ended? I believe you would rub your eyes, and feel sure that you were
+dreaming. Do not all rivers flow along their beds, growing larger with
+every mile, and finally empty their waters into a sea, or bay, or lake,
+or flow into some larger stream? This is the way of most rivers, but
+there are exceptions. In the Far West there are some great rivers that
+absolutely disappear before they reach a larger body of water. They
+simply sink away into the sand, and sometimes reappear to finish their
+courses after flowing underground for miles. Do you know the name of one
+great western river of which I am thinking? Is there any stream in your
+neighbourhood which has such peculiar ways?</p>
+
+<p>Down in Kentucky there is a region where, it is said, one may walk fifty
+miles without crossing running water. In the middle of our country, in
+the region of plentiful rainfall, and in a state covered with beautiful
+woodlands and famous for blue<span class='pagenum'><a name="Page_111" id="Page_111">[Pg 111]</a></span> grass and other grain crops, it is
+amazing that, over a large area, brooks and larger streams are lacking.
+In most of the state there is plenty of water flowing in streams like
+those in other parts of the eastern half of the United States. In the
+near neighbourhood of this peculiar section of the state the streams
+come to an end suddenly, pouring their water into funnel-shaped
+depressions of the ground called sink-holes. After a heavy rain the
+surface water, accumulating in rivulets, may also be traced to small
+depressions which seem like leaks in the earth's crust, into which the
+water trickles and disappears.</p>
+
+<p>It must have been noticed by the early settlers who came over the
+mountains from the eastern colonies, and settled in the new, wild, hilly
+country, which they called Kentucky. The first settlers built their log
+cabins along the streams they found, and shot deer and wild turkey and
+other game that was plentiful in the woods. The deer showed them where
+salt was to be found in earthy deposits near the streams; for salt is
+necessary to every creature. Deer trails led from many directions to the
+"salt licks" which the wild animals visited frequently.</p>
+
+<p>Perhaps the same pioneers who dug the salt out of the earth found
+likewise deposits of <i>nitre</i>, called also <i>saltpetre</i>, a very precious
+mineral, for it is one of the elements necessary in the manufacture of
+gunpowder. With the Indians all about him, and<span class='pagenum'><a name="Page_112" id="Page_112">[Pg 112]</a></span> often showing themselves
+unfriendly, the pioneer counted gunpowder a necessity of life. He relied
+on his gun to defend and to feed his family. There were men among those
+first settlers who knew how to make gunpowder, and saltpetre was one of
+the things that had to be carried across the mountains into Kentucky,
+until they found it in the hills. No wonder that prospectors went about
+looking for nitre beds in the overhanging ledges of rocks along
+stream-beds. In such situations the deposits of nitre were found. The
+earth was washed in troughs of running water to remove the clayey
+impurity. After a filtering through wood-ashes, the water which held the
+nitre in solution was boiled down, and left to evaporate, after which
+the crystals of saltpetre remained.</p>
+
+<p>Solid masses of saltpetre weighing hundreds of pounds were sometimes
+found in protected corners under shelving rocks. It was no doubt in the
+fascinating hunt for lumps of this pure nitre that the early prospectors
+discovered that the streams which disappeared into the sink-holes made
+their way into caverns underground. Digging in the sides of ravines
+often made the earthy wall cave in, and the surprised prospector stood
+at the door of a cavern. The discoverer of a cave had hopes that by
+entering he might find nitre beds richer than those he could uncover on
+the surface, and this often turned out to be true. The hope of finding
+precious metals and beds of iron ore also encouraged the exploration<span class='pagenum'><a name="Page_113" id="Page_113">[Pg 113]</a></span> of
+these caves. By the time the war of 1812 was declared, the mining of
+saltpetre was a good-sized industry in Kentucky. Most of the mineral was
+taken out of small caves, and shipped, when purified, over the
+mountains, on mule-back by trails, and in carts over good roads that
+were built on purpose to bring this mineral product to market. As long
+as war threatened the country, the Government was ready to buy all the
+saltpetre the Kentucky frontiersmen could produce. And the miners were
+constantly in search of richer beds that promised better returns for
+their labour.</p>
+
+<p>It was this search that led to the exploration of the caves discovered,
+although the explorer took his life in his hands when he left the
+daylight behind him and plunged into the under-world.</p>
+
+<p>Not all lost rivers tell as interesting stories or reveal as valuable
+secrets as did those the neighbours of Daniel Boone traced along their
+dark passages underground, and finally saw emerge as hillside springs,
+in many cases, to feed Kentucky rivers. But it is plain that no river
+sinks from sight unless it finds porous or honeycombed rocks that let it
+through. The water seeks the nearest and easiest route to the sea. Its
+weight presses toward the lowest level, always. The more water absorbs
+of acid, the more powerfully does it attack and carry away the substance
+of lime rocks through which it passes.<span class='pagenum'><a name="Page_114" id="Page_114">[Pg 114]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_MAMMOTH_CAVE_OF_KENTUCKY" id="THE_MAMMOTH_CAVE_OF_KENTUCKY"></a>THE MAMMOTH CAVE OF KENTUCKY</h2>
+
+
+<p>There is no more fertile soil in the country than that of the famous
+blue grass region of Kentucky. The surface soil rests upon a deep
+foundation of limestone rocks, and very gradually the plant food locked
+up in these underlying strata is pulled up to the surface by the soil
+water, and greedily appropriated by the roots of the plants.</p>
+
+<p>Part of the water of the abundant rainfall of this region soaks into the
+layers of the lime rock, carrying various acids in solution which give
+it power to dissolve the limestone particles, and thus to make its way
+easily through comparatively porous rock to the very depths of the
+earth. So it has come about that the surface of the earth is undermined.
+Vast empty chambers have been carved by the patient work of trickling
+water, which has carried away the lime that once formed solid and
+continuous layers of the earth's crust. We must believe that the work
+has taken thousands of years, at least, for no perceptible change has
+come to these wonderful caves since the discovery and exploration of
+them a century and more ago.</p>
+
+<p>The streams that flow into the region of these caves disappear suddenly
+into sink-holes and flow<span class='pagenum'><a name="Page_115" id="Page_115">[Pg 115]</a></span> through caverns. After wearing away their
+subterranean channels, leaping down from one level to another, forming
+waterfalls and lakes, some emerge finally through hillsides in the form
+of springs.</p>
+
+<p>The cavern region of Kentucky covers eight thousand square miles. The
+underground chambers found there are in the limestone rock which varies
+from ten to four hundred feet in thickness, and averages a little less
+than two hundred feet. Over this territory the number of sink-holes
+average one hundred to the square mile; and the streams that have poured
+their water into these basins have made a network of open caverns one
+hundred thousand miles in length.</p>
+
+<p>A great many small caverns have been thoroughly explored and are famous
+for their beauty. The Diamond Cave is one of the most splendid, for it
+is lined with walls and pillars of alabaster that sparkle in the
+torchlight with crystals that look like veritable diamonds. Beautiful
+springs and waterfalls are found in many caves, but the grandest of all
+is the Mammoth Cave, beside which no other is counted worthy to be
+compared.</p>
+
+<p>Great tales the miners told of the wonder and the beauty of these
+caverns, the walls of which were supported by arching alabaster columns
+and wonderful domes, of indescribable beauty of form and colouring. In
+1799, the year that Washington died, a pioneer discovered the entrance
+to a cave, the size and beauty of which surpassed anything he had<span class='pagenum'><a name="Page_116" id="Page_116">[Pg 116]</a></span> seen
+before. After exploring it for a short distance he returned home and
+took his whole family with him to enjoy the first view of the wonderful
+cavern he had discovered. They carried pine knots and a lighted torch,
+by which they made their way for some distance, but the torch was
+accidentally extinguished and they groped their way in darkness and
+missed the entrance. Without anything to guide them, they wandered in
+darkness for three days, and were almost dead when at last they stumbled
+upon the exit. This is the doorway of the Mammoth Cave of Kentucky, one
+of the wonders of the world.</p>
+
+<p>This was a terrible experience. The next persons who attempted to
+explore the new cave were better provisioned against the chance of
+spending some time underground. The pioneers found rich deposits of
+nitre in the "Great Cave," as they called it. Scientists visited it and
+explored many of its chambers. The reputation of this cavern has been
+spread by thousands of visitors who have come from all over the world to
+see it. The cave has not yet been completely explored. The regular
+tours, on which the guides conduct visitors, cover but a small part of
+the one hundred and fifty miles measured by the two hundred or more
+avenues. The passages wind in and out, crossing each other, sometimes at
+different levels, and forming a network of avenues in which the
+unaccustomed traveller would surely be lost. The old guides know every
+inch of their regular<span class='pagenum'><a name="Page_117" id="Page_117">[Pg 117]</a></span> course, and their quaint and edifying talk adds
+greatly to the pleasure of the visitors.</p>
+
+<p>From the hotel, parties are organized for ten o'clock in the morning and
+seven o'clock in the evening. Each visitor is provided with a lard-oil
+lamp. The guide carries a flask of oil and plenty of matches. No special
+garb is necessary, though people usually dress for comfort, and wear
+easy shoes. The temperature of the cave is uniform winter and summer,
+varying between fifty-three and fifty-four degrees Fahrenheit.</p>
+
+<p>The cave entrance is an arch of seventy-foot span in the hillside. A
+winding flight of seventy stone steps leads the party around a
+waterfall, into a great chamber under the rocks. Then the way goes
+through a narrow passage, where the guide unlocks an iron gate to let
+them in. The visitors now leave all thoughts of daylight behind, for the
+breeze that put out their lights as they entered the cave is past, and
+they stand in the Rotunda, a vast high-ceilinged chamber, silent and
+impressive, with walls of creamy limestone, encrusted with gypsum, which
+has been stained black by manganese. From the vestibule on, each passage
+and each room has a name, based upon some historic event or some fancied
+resemblance. The Giant's Coffin is a great kite-shaped rock lying in one
+of the rooms of the cave. The Star Chamber has a wonderful
+crystal-studded dome in which the guide produces the effect of a sunrise
+by burning coloured lights. Bonfires built at suitable<span class='pagenum'><a name="Page_118" id="Page_118">[Pg 118]</a></span> points produce
+wonderful shadow effects, which are like nothing else in the world. The
+old saltpetre vats which the visitors pass in taking the "Long Route"
+through the cave, point them back to the days during the War of 1812,
+when this valuable mineral was extracted from the earth in the floor of
+the cave. The industry greatly enriched the thrifty owners of the cave,
+but the works were abandoned after peace was declared.</p>
+
+<p>It must be a wonderful experience to walk steadily for nine hours over
+the Long Route, for so pure is the air and so wonderful is the scenery
+that people rarely complain of fatigue when the experience is over.
+There is no dust on the floors of these subterranean chambers, and they
+are not damp except near places where water trickles, here and there, in
+rivulets and cascades. Pools of water at the bottoms of pits so deep
+that a lighted torch requires several seconds to reach the bottom, and
+rivers and lakes of considerable size, show where some of the surface
+water goes to. A strange underground suction creates whirlpools in some
+of these streams. People go in boats holding twenty passengers for a row
+on Echo River, and the guide dips up with a net the blind fish and
+crayfish and cave lizards which inhabit these subterranean waters. The
+echoes in various chambers of the Mammoth Cave are remarkable. In some
+of them a song by a single voice comes back with full chords, as if
+several voices carried the different parts. The single notes of<span class='pagenum'><a name="Page_119" id="Page_119">[Pg 119]</a></span> flute
+and cornet are returned with the same beautiful harmonies. A pistol shot
+is given back a dozen times, the sound rebounding like a ball from rock
+to rock of the arching walls. The vibrations of the water made by the
+rower's paddles re&euml;cho in sounds like bell notes, and they are
+multiplied into harmonies that suggest the chimes in the belfry of a
+cathedral.</p>
+
+<p>The walls of various chambers differ from each other according to the
+minerals that compose them. Some are creamy white limestone arches, some
+are walled with black gypsum, some are hung with great curtains of
+stalagmites, solid but suggesting the lightness and grace of folds of
+cr&ecirc;pe. Under such hangings the floor is built up in stalactites. The
+mineral-laden water, the constant drip of which has produced a hanging,
+icicle-like stalagmite, has built up the stalactite to meet it.</p>
+
+<p>Probably nothing is more beautiful than the flower-like crystals that
+bloom all over the walls of a chamber called "Mary's Bower." The floor,
+even, sparkles with jewels that have fallen from the wonderful and
+delicate flower clusters built from deposits of the lime-laden water
+which goes on building and replacing the bits that fall. "Martha's
+Vineyard" is decorated with nodules, like bunches of grapes, that
+glisten as if the dew were on them. The white gypsum in some caves makes
+the walls look as if they were carved out of snow. Still others have
+clear, transparent crystals that make them gleam in the<span class='pagenum'><a name="Page_120" id="Page_120">[Pg 120]</a></span> torches' light
+as if the walls were encrusted with diamonds.</p>
+
+<p>The cave region of Indiana is also famous. The great Wyandotte Cave in
+Crawford County is the most noted of many similar caverns. In some of
+the chambers, bats are found clinging to the ceiling, heads downward,
+like swarms of bees. The caverns of Luray, in Virginia, are complex and
+wonderful in their structure, and famous for the beautiful stalactites
+and stalagmites they contain. But there is no cave in this country so
+wonderful and so grand in its dimensions as the Mammoth Cave in
+Kentucky.<span class='pagenum'><a name="Page_121" id="Page_121">[Pg 121]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="LAND-BUILDING_BY_RIVERS" id="LAND-BUILDING_BY_RIVERS"></a>LAND-BUILDING BY RIVERS</h2>
+
+
+<p>Once a year, when the rainy season comes in the mountainous country
+south of Egypt, the old Nile floods its banks and spreads its slimy
+waters over the land, covering the low plains to the very edge of the
+Sahara Desert. The people know it is coming, and are prepared for this
+flood. We should think such an overflow of our nearest river a monstrous
+calamity, but the Egyptians bless the river which blesses them. They
+know that without the Nile's overflow their country would be added to
+the Desert of Sahara. In a short time after the overflow, the river
+reaches its highest point and begins to ebb. Canals lying parallel to
+its course are filled with water which is saved for use in the hot, dry
+summer. As the flood goes down, a deposit of slimy mud lies as a rich
+fertilizer on the land. It is this and the water which the earth has
+absorbed that make Egypt one of the most fertile agricultural countries
+in the world.</p>
+
+<p>The region covered by the Nile's overflow is the flood plain of this
+river. On this plain the Pyramids, the Sphinx, and other famous
+monuments of Egypt stand. The statue of Rameses II. built 3,000 years
+ago, has its base buried nine feet deep in<span class='pagenum'><a name="Page_122" id="Page_122">[Pg 122]</a></span> the rich soil made of Nile
+sediment. A well dug in this region goes through forty feet of this soil
+before striking the underlying sand. How many years ago did the first
+Nile overflow take place? We may begin our calculation by finding out
+the average yearly deposit. It is a slow process that accumulates but
+nine feet in 3,000 years. If you were in Egypt when the Nile went back
+into its banks, you would see that the scum it leaves in a single
+overflow adds not a great deal to the thickness of the soil. Possibly
+floods have varied in their deposits from year to year, so that any
+calculation of the time it took to build that forty feet of surface soil
+must be but a rough estimate. This much we know: it has been an
+uninterrupted process which has taken place within the present
+geological epoch, "the Age of Man."</p>
+
+<p>Not all the rich sediment the Nile brings down is left on the level
+flood plain along its course. A vast quantity is dumped at the river's
+mouth, where the tides of the Mediterranean check the river's current.
+Thus the great delta is formed. The broad river splits into many mouths
+that spread out like a fan and build higher and broader each year the
+mud-banks between the streams. Upper Egypt consists of river swamps.
+Lower Egypt, from Cairo to the sea, is the delta built by the river
+itself on sea bottom. From the head of the delta, where the river
+commences to divide, to the sea, is an area of 10,000 square miles made
+out of material contributed by<span class='pagenum'><a name="Page_123" id="Page_123">[Pg 123]</a></span> upper Egypt, and built by the river.
+Layer upon layer, it is constantly forming, but most rapidly during the
+season of floods.</p>
+
+<p>Coming closer home, let us look at the map of the Mississippi Valley.
+Begin as far north as St. Louis. For the rest of its course the
+Mississippi River flows through a widening plain of swamp land, flooded
+in rainy seasons. Through this swampy flood plain the river meanders;
+its current, heavily loaded with sediment, swings from one side to the
+other of the channel, building up here, wearing away there, and
+straightening its course when the curves become so sharp that their
+sides meet. Then the current breaks through the thin wall, and a bayou
+of still water is left behind.</p>
+
+<p>Below Baton Rouge the Mississippi breaks into many mouths, that spread
+and carry the water of the great river into the Gulf of Mexico. The Nile
+delta is triangular, like delta, [Greek: D], the fourth letter of the
+Greek alphabet; but the Mississippi's delta is very irregular. The main
+mouth of the river flows fifty miles out into the Gulf between
+mud-banks, narrow and low. At the tip it branches into several streams.</p>
+
+<p>From the mouth of the Ohio to the Gulf, the Mississippi flood plain
+covers 30,000 square miles. Over this area, sediment to an average depth
+of fifty feet has been laid down. In earlier times the river flooded
+this whole area, when freshets swelled its tributaries in the spring.
+The flood<span class='pagenum'><a name="Page_124" id="Page_124">[Pg 124]</a></span> plain then became a sea, in the middle of which the river's
+current flowed swiftly. The slow-flowing water on each side of the main
+current let go of its burden of sediment and formed a double ridge.
+Between these two natural walls the main river flowed. When its level
+fell, two side streams, running parallel with the main river drained the
+flood plains on each side into the main tributaries to right and left.
+These natural walls deposited when the river was in flood are called
+<i>levees</i>. Each heavy flood builds them higher, and the bed of the stream
+rises by deposits of sediment. So it happens that the level of the river
+bed is higher than the level of its flood plain.</p>
+
+<p>This is an interesting fact in geology. But the people who have taken
+possession of the rich flood plain of the Mississippi River, who have
+built their homes there, drained and cultivated the land, and built
+cities and towns on the areas reclaimed from swamps, recognize the
+elevation of the river bed as the greatest danger that threatens them.
+Suppose a flood should come. Even if it does not overflow the levees, it
+may break through the natural banks and thus overflow the cities and the
+farm lands to left and right.</p>
+
+<p>Instead of living in constant fear of such a calamity, the people of the
+Mississippi flood plain have sought safety by making artificial levees,
+to make floods impossible. These are built upon the natural levees. As
+the river bed rises by the deposit of mud,<span class='pagenum'><a name="Page_125" id="Page_125">[Pg 125]</a></span> the levees are built higher
+to contain the rising waters. No longer does the rich soil of the
+Mississippi flood plain receive layers of sediment from the river's
+overflow. The river very rarely breaks through a levee. The United
+States Government has spent great sums in walling in the river, and each
+state along its banks does its share toward paying for this
+self-protection.</p>
+
+<p>By means of <i>jetties</i> the river's current is directed into a
+straightened course, and its power is expended upon the work of
+deepening its own channel and carrying its sediment to the Gulf. Much as
+the river has been forced to do in cleaning its own main channel,
+dredging is needed at various harbours to keep the river deep enough for
+navigation. The forests of the mountain slopes in Colorado are being
+slaughtered, and the headwaters of the Missouri are carrying more and
+more rocky d&eacute;bris to choke the current of the Mississippi. Colorado soil
+is stolen to build land in the vast delta, which is pushing out into the
+Gulf at the rate of six miles in a century&mdash;a mile in every sixteen
+years. The Mississippi delta measures 14,000 square miles. With the
+continued denuding of mountain slopes, we shall expect the rate of delta
+growth to be greatly increased, until reforesting checks the destructive
+work of wind and water.<span class='pagenum'><a name="Page_126" id="Page_126">[Pg 126]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_MAKING_OF_MOUNTAINS" id="THE_MAKING_OF_MOUNTAINS"></a>THE MAKING OF MOUNTAINS</h2>
+
+
+<p>The gradual thickening and shrinking of the earth's crust as it cools
+have made the wrinkles we call mountain systems. Through millions of
+years the globe has been giving off heat to the cold sky spaces through
+which it swings in its orbit around the sun. The cooling caused the
+contraction of the outer layer to fit the shrinking of the mass. When a
+plump peach dries on its pit, the skin wrinkles down to fit the dried
+flesh. The fruit shrinks by loss of water, just as the face of an old
+person shrinks by loss of fat. The skin becomes wrinkled in both cases.</p>
+
+<p>The weakest places in the earth's crust were the places to crumple,
+because they could not resist the lateral pressure that was exerted by
+the shrinking process. Along the shores of the ancient seas the rivers
+piled great burdens of sediment. This caused the thin crust to sink and
+to become a basin alongside of a ridge. The wearing away of the land in
+certain places lightened and weakened the crust at these places, so that
+it bent upward in a ridge.</p>
+
+<p>Perhaps the first wrinkles were not very high and deep. The gradual
+cooling must have exerted continued pressure, and the wrinkles have
+become larger.<span class='pagenum'><a name="Page_127" id="Page_127">[Pg 127]</a></span> It is not likely that new wrinkles would be formed as
+long as the old ones would crumple and draw up into narrower, steeper
+slopes, in response to the lateral crushing.</p>
+
+<p>We can imagine those first mountains rising as folds under the sea.
+Gradually their bases were narrowed, and their crests lifted out of the
+water. They rose as long, narrow islands, and grew in size as time went
+on.</p>
+
+<p>Why is the trend of the great mountain systems almost always north and
+south? Study the map of the continents and see how few cross ranges are
+shown, and how short they are, compared with the others. The molten
+globe bulged at its equator, as it rotated on its axis. The moon added
+its strong pulling force to make it bulge still more. As the crust
+thickened, it became less responsive to the two forces that caused it to
+bulge. The shrinkage was greatest where the globe had been most pulled
+out of shape. The rate of the earth's rotation is believed to have
+diminished. Every change tended to let the earth draw in its (imaginary)
+belt, a notch at a time. The forces of contraction acted along the line
+of the equator, and formed folds running toward the poles. In this early
+time the great mountain systems were born, and they grew in size
+gradually, from small beginnings.</p>
+
+<p>These mountains of upheaval, made by the bending of the earth's crust,
+and the formation of alternating ridges and depressed valleys, are many.
+The<span class='pagenum'><a name="Page_128" id="Page_128">[Pg 128]</a></span> earth is old and much wrinkled. Other mountains have been formed by
+forces quite different. Volcanic mountains have been far more numerous
+in ages gone than they are now.</p>
+
+<p>Mt. Hood and Mt. Rainier are peaks built up by the materials thrown out
+of the craters of volcanoes dead these thousands of years. Vesuvius is
+at present showing us how volcanic mountains are made. Each eruption
+builds larger the cone&mdash;that is, the chimney through which the molten
+rocks, the ashes, and the steam are ejected. Side craters may open, the
+main cone be broken and its form changed, but the mass of lava and
+stones and ashes grows with each eruption. The mountain grows by the
+additions it receives. &AElig;tna is a mountain built of lava.</p>
+
+<p>A third mountain system grew, not by addition, but by subtraction. The
+Catskills illustrate this type. This group of mountains is the remnant
+of a table-land made of level layers of red sandstone. The rest of the
+high plain has been cut down and carried away, leaving these picturesque
+hills, the survival of which is as much a mystery as the disappearance
+of the balance of the plateau of which they were once a part.</p>
+
+<p>The fold that forms a typical mountain ridge has a cone of granite, the
+original rock foundation of the earth, and on this are layers of
+stratified rock, ancient deposits of sediment carried to the sea by
+streams. When exposed to wind and rain, the<span class='pagenum'><a name="Page_129" id="Page_129">[Pg 129]</a></span> ridge is gradually worn
+down. In some places the water cuts away the soft rock and forms a
+stream-bed, that cuts deeper and deeper, using the rock fragments as its
+tools. Often the layers of aqueous rocks are cut through, and the
+granite exposed.</p>
+
+<p>Sometimes the hardest stratified rock-beds resist the water and the wind
+and are left as a series of ridges along the sides of the main range.
+The crumpling forces may crack the ridge open for its whole length, and
+one side of the chasm may slip down and the other go up. The result is a
+sheer wall of exposed rock strata, layers of which correspond with those
+that lie far below the top of the portion that slid down in the great
+upheaval and subsidence that parted them. These slips are known as
+<i>faults</i>.<span class='pagenum'><a name="Page_130" id="Page_130">[Pg 130]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_LAVA_FLOOD_OF_THE_NORTHWEST" id="THE_LAVA_FLOOD_OF_THE_NORTHWEST"></a>THE LAVA FLOOD OF THE NORTHWEST</h2>
+
+
+<p>We know little about the substance that occupies the four thousand miles
+of distance between the surface and the centre of our earth. We know
+that the terrible weight borne by the central mass compresses it, so
+that the interior must grow denser as the core is approached. Scientists
+have weighed the earth, and tell us that the crust is lighter than the
+rest. The supposition is that there is a great deal of iron in the
+interior, and possibly precious metals, too.</p>
+
+<p>Our deepest wells and mines go down about a mile, then digging stops, on
+account of the excessive heat. But the crumpling of the crust, and the
+wearing away of the folded strata by wind and running water, have laid
+bare rocks several miles in thickness on the slopes of mountains, and
+exposed the underlying granite, on which the first sedimentary rocks
+were deposited. On this granite lie stratified rocks, which are
+crystalline in texture. These are the beds, sometimes miles in depth,
+called <i>metamorphic</i> rocks, formed by water, then transformed by heat.</p>
+
+<p>The wearing away of rocks by wind and water has furnished the materials
+out of which the aqueous<span class='pagenum'><a name="Page_131" id="Page_131">[Pg 131]</a></span> rocks have been made. Layers upon layers of
+sandstone, shales, limestone, and the like, are exposed when a river
+cuts a canyon through a plateau. The layered deposits of d&eacute;bris at the
+mouth of the river make new aqueous rocks out of old. Every sandy beach
+is sandstone in the making. This work is never ended.</p>
+
+<p>In the early days the earth's crust often gaped open in a mighty crater
+and let a flood of lava overspread the surface. The ocean floor often
+received this flood of melted rock. In many places the same chimney
+opened again and again, each time spreading a new layer of lava on top
+of the old, so that the surface has several lava sheets overlying the
+aqueous strata.</p>
+
+<p>If the hardened lava sheet proved a barrier to the rising tide of molten
+lava in the chimney it was often forced out in sheets between the layers
+of aqueous rocks. Wherever the heated material came into contact with
+aqueous rocks it transformed them, for a foot or more, into crystalline,
+metamorphic rocks.</p>
+
+<p>A chimney of lava is called a <i>dike</i>. In mountainous countries dikes are
+common. Sometimes small, they may also be hundreds of feet across, often
+standing high above the softer strata, which rains have worn away. Dikes
+often look like ruined walls, and may be traced for miles where they
+have been overturned in the mountain-making process.</p>
+
+<p>The great lava flood of the Northwest happened<span class='pagenum'><a name="Page_132" id="Page_132">[Pg 132]</a></span> when the Coast Range was
+born. Along the border of the Pacific Ocean vast sedimentary deposits
+had accumulated during the Cretaceous and Tertiary Periods. Then the
+mighty upheaval came, the mountain ridge rose at the end of the Miocene
+epoch and stretched itself for hundreds of miles through the region
+which is now the coast of California and Oregon. Great fissures opened
+in the folded crust, and floods of lava overspread an area of 150,000
+square miles. A dozen dead craters show to-day where those immense
+volcanic chimneys were. The depth of the lava-beds is well shown where
+the Columbia River has worn its channel through. Walls of lava three
+thousand feet in thickness rise on each side of the river. They are made
+of columns of basalt, fitted together, like cells of a honeycomb, and
+jointed, forming stone blocks laid one upon another. The lava shrinks on
+cooling and forms prisms. In Ireland, the Giants' Causeway is a famous
+example of basaltic formation. In Oregon, the walls of the Des Chutes
+River show thirty lava layers, each made of vertical basalt columns. The
+palisades of the Hudson, Mt. Tom, and Mt. Holyoke are examples on the
+eastern side of the continent of basaltic rocks made by lava floods.</p>
+
+<p>Northern California, northwestern Nevada, and large part of Idaho,
+Montana, Oregon, and Washington are included in the basin filled with
+lava at the time of the great overflow, which extended far into British
+Columbia. It is probable that certain<span class='pagenum'><a name="Page_133" id="Page_133">[Pg 133]</a></span> chimneys continued to discharge
+until comparatively recent times. Mt. Rainier, Mt. Shasta, and Mt. Hood
+are among dead volcanoes.</p>
+
+<p>Quite a different history has the great Deccan lava-field of India,
+which covers a larger area than the basin of our Northwest, and is in
+places more than a mile in depth. It has no volcanoes, nor signs of any
+ever having existed. The floods alone overspread the region, which shows
+no puny "follow-up system" of scattered craters, intermittently in
+eruption.<span class='pagenum'><a name="Page_134" id="Page_134">[Pg 134]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_FIRST_LIVING_THINGS" id="THE_FIRST_LIVING_THINGS"></a>THE FIRST LIVING THINGS</h2>
+
+
+<p>Strange days and nights those must have been on the earth when the great
+sea was still too hot for living things to exist in it. The land above
+the water-line was bare rocks. These were rapidly being crumbled by the
+action of the air, which was not the mild, pleasant air we know, but was
+full of destructive gases, breathed out through cracks in the thin crust
+of the earth from the heated mass below. If you stand on the edge of a
+lava lake, like one of those on the islands of the Hawaiian group, the
+stifling fumes that rise might make you feel as if you were back at the
+beginning of the earth's history, when the solid crust was just a thin
+film on an unstable sea of molten rock, and this volcano but one of the
+vast number of openings by which the boiling lava and the condensed
+gases found their way to the surface. Then the rivers ran black with the
+waste of the rocky earth they furrowed, and there was no vegetation to
+soften the bleakness of the landscape.</p>
+
+<p>The beginnings of life on the earth are a mystery. Nobody can guess the
+riddle. The earliest rocks were subjected to great heat. It is not
+possible that life could have existed in the heated ocean or on the<span class='pagenum'><a name="Page_135" id="Page_135">[Pg 135]</a></span>
+land. Gradually the shores of the seas became filled up with sediment
+washed down by the rivers. Layer on layer of this sediment accumulated,
+and it was crumpled by pressure, and changed by heat, so that if any
+plants or animals had lived along those old shores their remains would
+have been utterly destroyed.</p>
+
+<p>Rocks that lie in layers on top of these oldest, fire-scarred
+foundations of the earth show the first faint traces of living things.
+Limestone and beds of iron ore are signs of the presence of life. The
+first animals and plants lived in the ancient seas.</p>
+
+<p>From the traces that are left, we judge that the earliest life forms
+were of the simplest kind, like some plants and animals that swim in a
+drop of water. Have you ever seen a drop of pond water under a compound
+microscope? It is a wonder world you look into, and you forget all the
+world besides. You are one of the wonderful higher animals, the highest
+on the earth. You focus on a shapeless creature that moves about and
+feels and breathes, but hasn't any eyes or mouth or stomach&mdash;in fact, it
+is the lowest form of animal life, and one of the smallest. It is but
+one of many animal forms, all simple in structure, but able to feed and
+grow and reproduce their kind.</p>
+
+<p>Gaze out of the window on the garden, now. The flowering plants, the
+green grass, and the trees are among the highest forms of plants. In the
+drop of<span class='pagenum'><a name="Page_136" id="Page_136">[Pg 136]</a></span> water under the microscope tiny specks of green are floating.
+They belong to the lowest order of plants. Among the plant and the
+animal forms that have been studied and named, are a few living things
+the places of which in the scale are not agreed upon. Some say they are
+animals; some believe they are plants. They are like both in some
+respects. It is probable that the first living things were like these
+confusing, minute things&mdash;not distinctly plants or animals, but the
+parent forms from which, later on, both plants and animals sprang.</p>
+
+<p>The lowest forms of life, plant and animal, live in water to-day. They
+are tiny and their bodies are made of a soft substance like the white of
+an egg. If these are at all like the living creatures that swarmed in
+the early seas, no wonder they left no traces in the rocks of the early
+part of the age when life is first recorded by fossils. Soft-bodied
+creatures never do.</p>
+
+<p>Some of the animals and the plants in the drop of water under the
+microscope have body walls of definite shapes, made of lime, or of a
+glassy substance called silica. When they die, these "skeletons" lie at
+the bottom of the water, and do not decay, as the living part of the
+body does, because they are mineral. Gradually a number of these shells,
+or hard skeletons, accumulate. In a glass of pond water they are found
+at the bottom, amongst the sediment. In a pond how many thousands of
+these<span class='pagenum'><a name="Page_137" id="Page_137">[Pg 137]</a></span> creatures must live and their shells fall to the bottom at last,
+buried in the mud!</p>
+
+<p>So it is easy to understand why the first creatures on earth left no
+trace. The first real fossils found in the rocks are the hard shells or
+skeletons of the first plants and animals that had hard parts.<span class='pagenum'><a name="Page_138" id="Page_138">[Pg 138]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="AN_ANCIENT_BEACH_AT_EBB_TIDE" id="AN_ANCIENT_BEACH_AT_EBB_TIDE"></a>AN ANCIENT BEACH AT EBB TIDE</h2>
+
+
+<p>When the tide is out, the rocks on the Maine coast have plenty of living
+creatures to prove this northern shore inhabited. Starfishes lurk in the
+hollows, and the tent-shaped shells of the little periwinkle encrust the
+wet rocks. Mussels cling to the rocks in clumps, fastened to each other
+by their ropes of coarse black hair. The furry coating of sea mosses
+that encrust the rocks is a hiding-place for many kinds of living
+things, some soft-bodied, some protected by shells. The shallow water is
+the home of plants and animals of many different kinds. As proof of this
+one finds dead shells and fragments of seaweeds strewn on the shore
+after a storm.</p>
+
+<p>Along the outer shores of the Cape Cod peninsula and down the Jersey
+coast, the sober colouring of the shells of the north gives way to a
+brighter colour scheme. In the warmer waters, life becomes gayer, if we
+may judge by the rich tints that ornament the shells. The kinds of
+living creatures change. They are larger and more abundant. The seaweeds
+are more varied and more luxuriant in growth.</p>
+
+<p>When we reach the shores of the West Indian islands and the keys of
+Florida the greatest abundance and variety of living forms are found.
+The<span class='pagenum'><a name="Page_139" id="Page_139">[Pg 139]</a></span> submerged rocks blossom with flower-like sea anemones of every
+colour. Corals, branching like trees and bushes on the sea floor, form
+groves under water. Among them brilliant-hued fishes swim, and highly
+ornamented shells glide, as people know who have gazed through the glass
+bottoms of the boats built especially to show visitors the wonderful sea
+gardens at Nassau, Bahama Islands, and at Santa Catalina Island,
+southern California.</p>
+
+<p>On every beach the skeletons of animals which die help to build up the
+land; though the process is not so rapid in the north as on the shores
+that approach the tropics. The coast of Florida has a rim of island
+reefs around it built out of coral limestone. Indeed, the peninsula was
+built by coral polyps. Houses in St. Augustine are built of coquina
+rock, which is simply a mass of broken shells held together by a lime
+cement. Every sea beach is packed with shells and other remnants of
+animals and plants that live in the shallow waters. Deeper and deeper
+year by year the sand buries these skeletons, and many of them are
+preserved for all time.</p>
+
+<p>Thus what is sandy beach to-day may, a few million years from now, be
+uncovered as a ledge of sandstone with the prints of waves distinctly
+shown, and fossil shells of molluscs, skeletons of fishes, and branches
+of seaweed&mdash;all of them different from those then growing upon the
+earth.</p>
+
+<p>In the neighbourhood of Cincinnati there have been uncovered banks of
+stone accumulated along<span class='pagenum'><a name="Page_140" id="Page_140">[Pg 140]</a></span> the border of an ancient sea. From the sides of
+granite highlands streams brought down the sand built into these oldest
+sandstone rocks. The fine mud which now appears as beds of slate was the
+decay of feldspar and hornblende in the same granite. Limestone beds are
+full of the fossil shells of creatures that lived in the shallow seas.
+Their skeletons, accumulating on the bottom, formed deep layers of
+limestone mud. These rocks preserve, by the fossils they contain, a
+great variety of shellfish which had limy skeletons. The sea fairly
+swarmed along its shallow margin with these creatures. We might not
+recognize many of the shells and other curious fossils we find in the
+rock uncovered by the workmen who are cutting a railroad embankment.
+They are not exactly like the living forms that grow along our beaches
+to-day, but they are enough like them for us to know that they lived
+along the seashore, and if we had time to examine all the rocks of this
+kind preserved in a museum we should decide that seashore life was quite
+as abundant then as it is now. The pressed specimens of plants of those
+earliest seashores are mere imprints showing that they were pulpy and
+therefore gradually decayed. Only their shape is recorded by dark stains
+made by each branching part. The decay of the vegetable tissue painted
+the outline on the rock which when split apart shows us what those
+ancient seaweeds looked like. They belonged to the group of plants we
+call kelp, or tangle, which are still common enough in the sea, though
+the forms we now have are not exactly like the old ones. Seaweeds belong
+to the very lowest forms of plants.</p>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus140a_th.jpg" width="500" height="435" alt="Crinoid from Indiana" title="" />
+<span class="caption">Crinoid from Indiana</span>
+</div>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus140b_th.jpg" width="500" height="365" alt="By permission of the American Museum of Natural History
+
+Ammonite from Jurassic of England" title="" />
+<span class="caption">By permission of the American Museum of Natural History<br />
+Ammonite from Jurassic of England</span>
+</div>
+
+<div class="figcenter" style="width: 308px;">
+<img src="images/illus141_th.jpg" width="308" height="500" alt="By permission of the American Museum of Natural History
+
+Fossil corals Coquina, Hippurite limestone" title="" />
+<span class="caption">By permission of the American Museum of Natural History<br />
+Fossil corals Coquina, Hippurite limestone</span>
+</div><p><span class='pagenum'><a name="Page_141" id="Page_141">[Pg 141]</a></span></p>
+
+<p>The limestones are full of fossils of corals. Indeed, there must have
+been reefs like those that skirt Florida to-day built by these
+lime-building polyps. Their forms are so well preserved in the rocks
+that it is possible to know just how they looked when they grew in the
+shallows.</p>
+
+<p>One very common kind is called a cup coral, because the polyp formed a
+skeleton shaped like a cup. The body wall surrounded the skeleton, and
+the arms or tentacles rose from the centre of the funnel-like depression
+in the top. Little cups budded off from their parents, but remained
+attached, and at length the skeletons of all formed great masses of limy
+rock. Some cup corals grew in a solid mass, the new generation forming
+an outer layer, thus burying the parent cups.</p>
+
+<p>A second type of corals in these oldest limestones is the honeycomb
+group. The colonies of polyps lived in tubes which lengthened gradually,
+forming compact, limy cylinders like organ pipes, fitted close together.
+The living generation always inhabited the upper chambers of the tubes.
+A third type is the chain coral, made of tubes joined in rows, single
+file like pickets of a fence. But these walls bend into curious
+patterns, so that the cross-section of a mass of them looks like a
+complex pattern of crochet-work,<span class='pagenum'><a name="Page_142" id="Page_142">[Pg 142]</a></span> the irregular spaces fenced with chain
+stitches. Each open link is a pit in which a polyp lived.</p>
+
+<p>Among the corals are sprays of a fine feathery growth embedded in the
+limestone. Fine, straight, splinter-like branches are saw-toothed on one
+or both edges. These limy fossils might not be seen at all, were they
+not bedded in shales, which are very fine-grained. Here again are the
+skeletons of animals. Each notch on each thread-like branch was the home
+of a tiny animal, not unlike a sea anemone and a coral polyp.</p>
+
+<p>To believe this story it is necessary only to pick up a bit of dead
+shell or floating driftwood on which a feathery growth is found. These
+plumes, like "sea mosses," as they are called, are not plants at all,
+but colonies of polyps. Each one lived in a tiny pit, and these pits
+range one above the other, so as to look like notches on the thread-like
+divisions of the stem. Put a piece of this so-called "sea moss" in a
+glass of sea water, and in a few moments of quiet you will see, by the
+use of a magnifying glass, the spreading arms of the polyp thrust out of
+each pit.</p>
+
+<p>The ancient seas swarmed with these living hydrozoans, and their remains
+are found preserved as fossils in the shales which once were beds of
+soft mud.</p>
+
+<p>The hard shells of sea urchins and starfishes are made of lime. In the
+ancient seas, starfishes were rare and sea urchins did not exist, but
+all over the sea<span class='pagenum'><a name="Page_143" id="Page_143">[Pg 143]</a></span> bottom grew creatures called crinoids, the soft parts
+of which were enclosed in limy protective cases and attached to rocks on
+the sea bottom by means of jointed stems. No fossils are more plentiful
+in the early limestones than these wonderful "stone lilies." Indeed, the
+crinoidal limestone seemed to be built of the skeletons of these
+animals. The lily-like body was flung open, as a lily opens its calyx,
+when the creature was feeding. But any alarm caused the tentacles to be
+drawn in, and the petal-like divisions of the body wall to close tightly
+together, till that wall looked like an unopened bud.</p>
+
+<p>On the bottom of the Atlantic, near the Bahama Islands, these stone
+lilies are still found growing. Their jointed stems and body parts are
+as graceful in form and motion as any lily. The creature's mouth is in
+the centre of the flower-like top, and it feeds like the sea urchin, on
+particles obtained in the sea water.</p>
+
+<p>The old limestones contain great quantities of "lamp shells," which are
+old-fashioned bivalves. Their shells remind us of our bivalve clams and
+scallops, but the internal parts were very different. The gills of clams
+and oysters are soft parts. Inside of the lamp shells are coiled, bony
+arms, supporting the fringed gills.</p>
+
+<p>It is fortunate for us that a few lamp shells still live in the seas. By
+studying the soft parts of these living remnants of a very old race we
+can know the secrets of the lives of those ancient lamp shells,<span class='pagenum'><a name="Page_144" id="Page_144">[Pg 144]</a></span> the
+soft parts of which were all washed away, and the fossil shells of which
+are preserved. Gradually the lamp shells died out, and the modern
+bivalves have come to take their places. Just so, the ancient crinoids
+are now almost extinct; the sea urchins and the starfishes have
+succeeded them.</p>
+
+<p>The chambered nautilus has its shell divided by partitions and it lives
+in the outer chamber, a many-tentacled creature, that is a close
+relative of the soft-bodied squid. In the ancient seas the same family
+was represented by huge creatures the shells of which were chambered,
+but not coiled. Their abundance and great size are proved by the rocks
+in which their fossils are preserved. Some of them must have been the
+rulers of the sea, as sharks and whales are to-day. Fossil specimens
+have been found more than fifteen feet long and ten inches in diameter
+in the ancient rocks of some of the Western States. It is possible to
+read from the lowest rock formations upward, the rise of these sea
+giants and their gradual decline. Certain strata of limestone contain
+the last relics of this race, after which they became extinct. As the
+straight-chambered forms diminished, great coiled forms became more
+abundant, but all died out.</p>
+
+<p>One of the most abundant fossil animals in ancient rocks is called a
+trilobite. Its body is divided by two grooves into three parts, a
+central ridge extending the whole length of the body and two side
+ridges. The front portion of the shell formed the head shield,<span class='pagenum'><a name="Page_145" id="Page_145">[Pg 145]</a></span> and
+behind the main body part was a little tail shield. The skeleton was
+formed of many movable jointed plates, and the creature had eyes set in
+the head shield just as the king crab's are set. Jointed legs in pairs
+fringed each side of the body. Each leg had two branches, one for
+walking, the other for swimming. A pair of feelers rose from the head.
+The body could be rolled into a ball when danger threatened, by bringing
+head and tail together.</p>
+
+<p>These remarkable, extinct trilobites were the first crustaceans. Their
+nearest living relative to-day is the horseshoe crab. The fresh-water
+crayfish and the lobster are more distant relatives: so are the shrimps
+and the prawns. No such abundance of these creatures exists to-day as
+existed when the trilobites thronged the shallows. So well preserved are
+these skeletons that, although there are no living trilobites for
+comparison, it is possible to find out from the fossil enough about
+their structure to know how they fed and lived their lives along with
+the straight-horns which were the scavengers of those early seas and the
+terror of smaller creatures. The trilobites throve, and, dying, left
+their record in the rocks; then disappeared entirely. We find their
+fossils in a great variety of forms, shapes, and sizes. The smallest is
+but a fraction of an inch long, the largest twenty inches long.</p>
+
+<p>The ancient rocks, in which these lower forms of life have left their
+fossils, are known as the Silurian system. The time in which these rocks
+were accumulating<span class='pagenum'><a name="Page_146" id="Page_146">[Pg 146]</a></span> under the seas covers a vast period. We call it the
+Age of Invertebrates, because these soft-bodied, hard-shelled animals,
+the crinoids, the molluscs, and the trilobites, with bony external
+skeletons and no backbones, were the most abundant. They overshadowed
+all other forms of life. The rocks of this wonderful series were formed
+on the shores of a great inland sea that covered the central portion of
+North America. In the ages that followed, these rocks were covered
+deeply with later sediments. But the upheavals of the crust have broken
+open and erosion has uncovered these strata in different regions.
+Geologists have found written there, page upon page, the record of life
+as it existed in the early seas.<span class='pagenum'><a name="Page_147" id="Page_147">[Pg 147]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_LIME_ROCKS" id="THE_LIME_ROCKS"></a>THE LIME ROCKS</h2>
+
+
+<p>"Hard" water and "soft" water are very different. The rain that falls
+and fills our cisterns is not softer or more delightful to use than the
+well water in some favoured regions. In it, soap makes beautiful, creamy
+suds, and it is a real pleasure to put one's hands into it. But in hard
+water soap seems to curdle, and some softening agent like borax has to
+be added or the water will chap the hands. There is little satisfaction
+in using water of this kind for any purpose.</p>
+
+<p>Hard water was as soft as any when it fell from the sky; but the rain
+water trickled into the ground and passed through rocks containing lime.
+Some of this mineral was absorbed, for lime is readily soluble in water.
+Clear though it may be, water that has lime in it has quite a different
+feeling from rain water. Blow the breath into a basin of hard water, and
+a milky appearance will be noted. The carbonic acid gas exhaled from the
+lungs unites with the invisible lime, causing it to become visible
+particles of carbonate of lime, which fall to the bottom of the basin.</p>
+
+<p>Nearly all well water is hard. So is the water of lakes and rivers and
+the ocean, for limestone is one<span class='pagenum'><a name="Page_148" id="Page_148">[Pg 148]</a></span> of the most widely distributed rocks in
+the surface of the earth. Rain water makes its way into the earth's
+crust, absorbs mineral substances, and collects in springs which feed
+brooks and rivers and lakes. Wells are holes in the ground which bore
+into water-soaked strata of sand.</p>
+
+<p>We gain something from the lime dissolved in hard water, for it is an
+essential part of our food. We must drink a certain amount of water each
+day to keep the body in perfect health. The lime in this water goes
+chiefly to the building of our bones. Plant roots take up lime in the
+water that mounts as sap through the plant bodies. We get some of the
+lime we need in vegetable foods we eat.</p>
+
+<p>All of the kingdom of vertebrate animals, from the lowest forms to the
+highest, all of the shell-bearing animals of sea and land, require lime.
+Many of the lower creatures especially these in the sea, such as corals
+and their near relatives, encase themselves in body walls of lime. They
+absorb the lime from the sea water, and deposit it as unconsciously as
+we build the bony framework of our bodies.</p>
+
+<p>All the bone and shell-bearing creatures that die on the earth and in
+the sea restore to the land and to the water the lime taken by the
+creatures while they lived. Carbonic acid gas in the water greatly
+hastens the dissolving of dead shells. Carbonic acid gas, whether free
+in the air, or absorbed by percolating water, hastens the dissolving of
+skeletons of creatures that die upon land. Then the raw<span class='pagenum'><a name="Page_149" id="Page_149">[Pg 149]</a></span> materials are
+built again into lime rocks underground.</p>
+
+<p>The lime rocks are the most important group in the list of rocks that
+form the crust of the earth. They are made of the elements calcium,
+carbon, and oxygen, yet the different members of this calcite group
+differ widely in composition and appearance. So do oyster shells and
+beef bones, though both contain quantities of carbonate of lime.</p>
+
+<p>Calcite is a soft mineral, light in weight, sometimes white, but oftener
+of some other colour. It may be found crystallized or not. Whenever a
+drop of acid touches it, a frothy effervescence occurs. The drop of acid
+boils up and gives off the pungent odour of carbonic acid gas.</p>
+
+<p>The reason that calcite is hard to find in rocks is that percolating
+water, charged with acids, is constantly stealing it, and carrying it
+away into the ocean. The rocks that contain it crumble because the limy
+portions have been dissolved out.</p>
+
+<p>Some limestones resist the destructive action of water. When they are
+impregnated with silica they become transformed into marble, which takes
+a high polish like granite. Acids must be strong to make any impression
+on marble.</p>
+
+<p>The thick beds of pure limestone that underlie the surface soil in
+Kentucky and in parts of Virginia sometimes measure several hundred feet
+in thickness, a single stratum often being twenty feet thick. They are
+all horizontal, for they were formed on<span class='pagenum'><a name="Page_150" id="Page_150">[Pg 150]</a></span> sea bottom, and have not been
+crumpled in later time. The dead bodies of sea creatures contributed
+their shells and skeletons to the lime deposit on the sea bottom. Who
+can estimate the time it took to form those thick, solid layers of lime
+rock? The animals were corals, crinoids, and molluscs. Little sand and
+clay show in the lime rock of this period, before the marshes of the
+Carboniferous Age took the place of the ancient inland sea of the
+Subcarboniferous Period, the sedimentary accumulations of which we are
+now talking about.</p>
+
+<p>The living corals one sees in the shallow water of the Florida coast
+to-day are building land by building up their limy skeletons. The reefs
+are the dead skeletons of past generations of these tiny living things.
+They take in lime from the water, and use it as we use lime in building
+our bones. In each case it is an unconscious process of animal
+growth&mdash;not a "building process" like a mason's building of a wall. Many
+people think that the coral polyp builds in this way. They give it
+credit for patience in a great undertaking. All the polyp does is to
+feed on whatever the water supplies that its digestive organs can use.
+It is like a sea anemone in appearance and in habits of life. It is not
+at all like an insect. Yet it is common to hear people speak of the
+"coral insect"! Do not let any one ever hear you repeat such a mistake.</p>
+
+<p>Southern Florida is made out of coral rock, but thinly covered with
+soil. It was made<span class='pagenum'><a name="Page_151" id="Page_151">[Pg 151]</a></span> by the growth of reef after reef, and it is still
+growing.</p>
+
+<p>The Cretaceous Period of the earth's eventful history is named for the
+lime rock which we know as chalk. Beds of this recent kind of limestone
+are found in England and in France, pure white, made of the skeletons of
+the smallest of lime-consuming creatures, Foraminifera. They swarmed in
+deep water, and so did minute sponge animalcules and plant forms called
+Diatoms that took silica from the water, and formed their hard parts of
+this glassy substance. The result is seen in the nodules of flint found
+in the soft, snow-white chalk. Did you ever use a piece of chalk that
+scratched the black-board? The flint did it. Have you ever seen the
+chalk cliffs of Dover? When you do see them, notice how they gleam white
+in the sun. See how the rains have sculptured those cliffs. The
+prominences left standing out are strengthened by the flint they
+contain. Chalk beds occur in Texas and under our great plains; but the
+principal rocks of the age in America were sandstones and clays.<span class='pagenum'><a name="Page_152" id="Page_152">[Pg 152]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_AGE_OF_FISHES" id="THE_AGE_OF_FISHES"></a>THE AGE OF FISHES</h2>
+
+
+<p>The first animal with a backbone recorded its existence among the
+fossils found in rocks of the upper Silurian strata. It is a fish; but
+the earliest fossils are very incomplete specimens. We know that these
+old-fashioned fishes were somewhat like the sturgeons of our rivers.
+Their bodies were encased in bony armour of hard scales, coated with
+enamel. The bones of the spine were connected by ball and socket joints,
+and the heads were movable. In these two particulars the fishes
+resembled reptiles. The modern gar-pike has a number of the same
+characteristics.</p>
+
+<p>Another backboned creature of the ancient seas was the ancestral type of
+the shark family. In some points this old-fashioned shark reminds us of
+birds and turtles. These early fishes foreshadowed all later
+vertebrates, not yet on the earth. After them came the amphibians, then
+the reptiles, then the birds, and latest the mammals.</p>
+
+<p>The race of fishes began, no doubt, with forms so soft-boned that no
+fossil traces are preserved in the rocks. When those with harder bones
+appeared, the fossil record began, and it tells the story of the passing
+of the early, unfish-like forms, and the coming of new kinds, great in
+size and in numbers, that swarmed in the seas, and were tyrants over all
+other living things. They conquered the giant straight-horns and
+trilobites, former rulers of the seas.</p>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus152_th.jpg" width="500" height="309" alt="By permission of the American Museum of Natural History
+
+A sixteen-foot fossil fish from Cretaceous of Kansas, with a modern
+tarpon" title="" />
+<span class="caption">By permission of the American Museum of Natural History<br />
+A sixteen-foot fossil fish from Cretaceous of Kansas, with a modern
+tarpon</span>
+</div>
+
+<div class="figcenter" style="width: 349px;">
+<img src="images/illus153_th.jpg" width="349" height="500" alt="By permission of the American Museum of Natural History
+
+Ca&ntilde;on Diablo meteorite from Arizona" title="" />
+<span class="caption">By permission of the American Museum of Natural History<br />
+Ca&ntilde;on Diablo meteorite from Arizona</span>
+</div><p><span class='pagenum'><a name="Page_153" id="Page_153">[Pg 153]</a></span></p>
+
+<p>One of these giant fishes fifteen to twenty feet long, three feet wide,
+had jaws two feet long, set with blade-like teeth. Devonian rocks in
+Ohio have yielded fine fossils of gigantic fishes and sharks.</p>
+
+<p>Devonian fishes were unlike modern kinds in these particulars, the
+spinal column extended to the end of the tail, whether the fins were
+arranged equally or unequally on the sides; the paired side fins look
+like limbs fringed with fins. Every Devonian fish of the gar type seems
+to have had a lung to help out its gill-breathing.</p>
+
+<p>In these traits the first fishes were much like the amphibians. They
+were the parent stock from which branched later the true fishes and the
+amphibians, as a single trunk parts into two main boughs. The trunk is
+the connecting link.</p>
+
+<p>The sea bottom was still thronged with crinoids, and lamp shells, and
+cup corals. Shells of both clam and snail shapes are plentiful. The
+chambered straight-horns are fewer and smaller, and coiled forms of this
+type of shell are found. Trilobite forms are smaller, and their numbers
+decrease.</p>
+
+<p>The first land plants appeared during this age. Ferns and giant club
+mosses and cycads grew in swampy ground. This was the beginning of the<span class='pagenum'><a name="Page_154" id="Page_154">[Pg 154]</a></span>
+wonderful fern forests that marked the next age, when coal was formed.</p>
+
+<p>The rocks that bear the record of these living things in their fossils,
+form strata of great thickness that overlie the Silurian deposits. There
+is no break between them. So we understand that the sea changed its
+shore-line only when the Silurian deposits rose to the water-level.</p>
+
+<p>The Devonian sea was smaller than the Silurian. A great tract of
+Devonian deposits occupies the lower half of the state of New York,
+Canada between Lakes Erie and Huron, and the northern portions of
+Indiana and Illinois. These older layers of the stratified rock are
+covered with the deposits of later periods. Rivers that cut deep
+channels reveal the earlier rocks as outcrops along their canyon walk.
+The record of the age of fishes is, for the most part, still an unopened
+book. The pages are sealed, waiting for the geologist with his hammer to
+disclose the mysteries.<span class='pagenum'><a name="Page_155" id="Page_155">[Pg 155]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="KING_COAL" id="KING_COAL"></a>KING COAL</h2>
+
+
+<p>In this country, and in this age, who can doubt that coal is king? It is
+one of the few necessities of life. In various sections of the country,
+layers of coal have been discovered&mdash;some near the surface, others deep
+underground. These are the storehouses of fuel which the coal miners dig
+out and bring to the surface, and the railroads distribute. From
+Pennsylvania and Ohio to Alabama stretches the richest coal-basin.
+Illinois and Indiana contain another. From Iowa southward to Texas
+another broad basin lies. Central Michigan and Nova Scotia each has
+isolated coal-basins. All these have been discovered and mined, for they
+lie in the oldest part of the country.</p>
+
+<p>In the West, coal-beds have been discovered in several states, but many
+regions have not yet been explored. Vast coal-fields, still untouched,
+have been located in Alaska. The Government is trying to save this fuel
+supply for coming generations. Many of the richest coal-beds from Nova
+Scotia southward dip under the ocean. They have been robbed by the
+erosive action of waves and running water. Glaciers have ground away
+their substance, and given it to the sea. Much that remains intact<span class='pagenum'><a name="Page_156" id="Page_156">[Pg 156]</a></span> must
+be left by miners on account of the difficulties of getting out coal
+from tilted and contorted strata.</p>
+
+<p>As a rule, the first-formed coal is the best. The Western coal-fields
+belong to the period following the Carboniferous Age. Although
+conditions were favourable to abundant coal formation, Western coal is
+not equal to the older, Eastern coal. It is often called <i>lignite</i>, a
+word that designates its immaturity compared with anthracite.</p>
+
+<p>Coal formed in the Triassic Period is found in a basin near Richmond,
+Virginia. There is an abundance of this coal, but it has been subjected
+to mountain-making pressure and heat, and is extremely inflammable. The
+miners are in constant danger on account of coal gas, which becomes
+explosive when the air of the shaft reaches and mingles with it. This
+the miner calls "fire damp." North Carolina has coal of the same
+formation, that is also dangerous to mine, and very awkward to reach, on
+account of the crumpling of the strata.</p>
+
+<p>There are beds of coal so pure that very little ash remains after the
+burning. Five per cent, of ash may be reasonably expected in pure coal,
+unmixed with sedimentary deposits. Such coal was formed in that part of
+the swamp which was not stirred by the inflow of a river. Wherever muddy
+water flowed in among the fallen stems of plants, or sand drifted over
+the accumulated peat, these deposits remained, to appear later and
+bother those who attempt to burn the coal.</p>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus156a_th.jpg" width="500" height="281" alt="Eocene fish" title="" />
+<span class="caption">Eocene fish</span>
+</div>
+
+<div class="figcenter" style="width: 485px;">
+<img src="images/illus156b_th.jpg" width="485" height="500" alt="By permission of the American Museum of Natural History
+
+Trilobite from the Niagara limestone, Upper Silurian, of Western New
+York" title="" />
+<span class="caption">By permission of the American Museum of Natural History<br />
+Trilobite from the Niagara limestone, Upper Silurian, of Western New
+York</span>
+</div>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus157a_th.jpg" width="500" height="305" alt="Sigillaria, Stigmaria and Lepidodendron" title="" />
+<span class="caption">Sigillaria, Stigmaria and Lepidodendron</span>
+</div>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus157b_th.jpg" width="500" height="488" alt="By permission of the American Museum of Natural History
+
+Coal fern" title="" />
+<span class="caption">By permission of the American Museum of Natural History<br />
+Coal fern</span>
+</div><p><span class='pagenum'><a name="Page_157" id="Page_157">[Pg 157]</a></span></p>
+
+<p>You know pure coal, that burns with great heat and leaves but little
+ashes. You know also the other kind, that ignites with difficulty, burns
+with little flame, gives out little heat, and dying leaves the furnace
+full of ashes. You are trying to burn ancient mud that has but a small
+proportion of coal mixed with it. The miners know good coal from poor,
+and so do the coal dealers. It is not profitable to mine the impure part
+of the vein. It costs as much to mine and ship as the best quality, and
+it brings a much lower price.</p>
+
+<p>The deeper beds of coal are better than those formed in comparatively
+recent time and found lying nearer the surface. In many bogs a layer of
+embedded root fibres, called peat, is cut into bricks and dried for
+burning. Deeper than peat-beds lie the <i>lignites</i>, which are old beds of
+peat, on the way to become coal. <i>Soft coal</i> is older than lignite. It
+contains thirty to fifty per cent. of volatile matter, and burns
+readily, with a bright blaze. The richest of this bituminous coal is
+called <i>fat</i>, or <i>fusing coal</i>. The bitumen oozes out, and the coal
+cakes in burning. Ordinary soft coal contains less, but still we can see
+the resinous bitumen frying out of it as it burns. There is more heat
+and less volatile matter in <i>steam coal</i>, so-called because it is the
+fuel that most quickly forms steam in an engine. <i>Hard coal</i> contains
+but five to ten per cent. of volatile matter. It is slow to ignite and
+burns with a small blue blaze.<span class='pagenum'><a name="Page_158" id="Page_158">[Pg 158]</a></span></p>
+
+<p>From peat to anthracite coal I have named the series which increases
+gradually in the amount of heat it gives out, and increases and then
+decreases in its readiness to burn and in the brightness of its flame.
+Anthracite coal has the highest amount of fixed carbon. This is the
+reason why it makes the best fuel, for fixed carbon is the substance
+which holds the store of imprisoned sunlight, liberated as heat when the
+coal burns. Tremendous pressure and heat due to shrinking of the earth's
+crust have crumpled and twisted the strata containing coal in eastern
+Pennsylvania, and thus changed bituminous coal into anthracite. Ohio
+beds, formed at the same time, but undisturbed by heat and pressure, are
+bituminous yet.</p>
+
+<p>The coal-beds of Rhode Island are anthracite, but the coal is so hard
+that it will not burn in an open fire. The terrible, mountain-making
+forces that crumpled these strata and robbed the coal of its volatile
+matter, left so little of the gas-forming element, that a very special
+treatment is necessary to make the carbon burn. It is used successfully
+in furnaces built for the smelting of ores.</p>
+
+<p>The last stage in the coal series is a black substance which we know as
+black lead, or graphite. We write with it when we use a "lead" pencil.
+This is anthracite coal after all of the volatile matter has been driven
+out of it. It cannot burn, although it is solid carbon. The beds of
+graphite have been formed out of coal by the same changes in the<span class='pagenum'><a name="Page_159" id="Page_159">[Pg 159]</a></span>
+earth's crust which have converted soft coal into anthracite.</p>
+
+<p>The tremendous pressure that bears on the coal measures has changed a
+part of the carbon into liquid and gaseous form. Lakes of oil have been
+tapped from which jets of great force have spouted out. Such
+accumulations of oil usually fill porous layers of sandstone and are
+confined by overlying and underlying beds of impervious clay. Gas may be
+similarly confined until a well is drilled, relieving the pressure, and
+furnishing abundant or scanty supply of this valuable fuel. Western
+Pennsylvania coal-fields have beds of gas and oil. If mountain-making
+forces had broken the strata, as in eastern Pennsylvania, the gas and
+the oil would have been lost by evaporation.</p>
+
+<p>This is what happened in the anthracite coal-belt.<span class='pagenum'><a name="Page_160" id="Page_160">[Pg 160]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="HOW_COAL_WAS_MADE" id="HOW_COAL_WAS_MADE"></a>HOW COAL WAS MADE</h2>
+
+
+<p>The broad, rounded dome of a maple tree shades my windows from the
+intense heat of this August day. The air is hot, and every leaf of the
+tree's thatched roof is spread to catch the sunlight. The carbon in the
+air is breathed in through openings on the under side of each leaf. The
+sap in the leaf pulp uses the carbon in making starch. The sun's heat is
+absorbed. It is the energy that enables the leaf-green to produce a
+wonderful chemical change. Out of soil water, brought up from the roots,
+and the carbonic acid gas, taken in from the air, rich, sugary starch is
+manufactured in the leaf laboratory.</p>
+
+<p>This plant food returns in a slow current, feeding the growing cells
+under the bark, from leaf tip to root tip, throughout the growing tree.
+The sap builds solid wood. The maple tree has been built out of muddy
+water and carbon gas. It stands a miracle before our eyes. In its tough
+wood fibres is locked up all the heat its leaves absorbed from the sun,
+since the day the maple seed sprouted and the first pair of leaves
+lifted their palms above the ground.</p>
+
+<p>If my maple tree should die, and fall, and lie undisturbed<span class='pagenum'><a name="Page_161" id="Page_161">[Pg 161]</a></span> on the
+ground, it would slowly decay. The carbon of its solid frame would pass
+back into the air, as gas, and the heat would escape so gradually that I
+could not notice it at all, unless I thrust my hand into the warm,
+crumbling mass.</p>
+
+<p>If my tree should be cut down to-day and chopped into stove wood, it
+would keep a fire in my grate for many months.</p>
+
+<p>Burning destroys wood substance a great deal faster than decay in the
+open air does, but the processes of rotting and burning are alike in
+this: each process releases the carbon, and gives it back to the air. It
+gives back also the sun's heat, stored while the tree was growing. There
+is left on the ground, and in the ashes on the hearth, only the mineral
+substance taken up in the water the roots gathered underground.</p>
+
+<p>If my tree stood in swampy ground and fell over under a high wind, the
+water that covered it and saturated its substance would prevent decay.
+The carbon would not be allowed to escape as a gas to the air; the woody
+substance would become gradually changed into <i>peat</i>. In this form it
+might remain for thousands of years, and finally be changed into coal.</p>
+
+<p>Whether it was burned while yet in the condition of peat, or millions of
+years later, when it was transformed into coal, the heat stored in its
+substance was liberated by the burning. The carbon and the heat went
+back to the air.</p>
+
+<p>Every green plant we see spreads its leaves to the<span class='pagenum'><a name="Page_162" id="Page_162">[Pg 162]</a></span> sun. Every stick of
+wood we burn, and every lump of coal, is giving back, in the form of
+light and heat, the energy that came from sunshine and was captured by
+the green leaves. How long the wood has held this store of heat we may
+easily compute, for we can read the age of a tree. But the age of coal
+we cannot accurately state. The years probably should be counted by
+millions, instead of thousands.</p>
+
+<p>The great inland sea that covered the middle portion of the continent
+during the Silurian and the Devonian periods, became shallow by the
+deposit of vast quantities of sediment. Along the lines of the deposits
+of greatest thickness, a crumpling of the earth's crust lifted the first
+fold of the Alleghany Mountains as a great sea wall on the east, and on
+the western shore another formed the beginning of the Ozark Mountain
+system in Missouri. An island was lifted out of the sea, forming the
+elevated ground on which the city of Cincinnati now stands. Various
+other ridges and islands divided the ancient sea into much smaller
+bodies of water. Hemmed in by land these shallow sea-basins gradually
+changed into fresh-water lakes, for they no longer had connection with
+the ocean, and all the water they received came from rain. After
+centuries of freshets, and of filling in with the rock d&eacute;bris brought by
+the streams, they became great marshes, in which grew water-loving
+plants. Generation after generation of these plants died, and their
+remains, submerged by the water, were converted into peat. In the<span class='pagenum'><a name="Page_163" id="Page_163">[Pg 163]</a></span>
+course of ages this peat became coal. This is the history of the coal
+measures.</p>
+
+<p>There is no guesswork here. The stems of plants do not lose their
+microscopic structure in all the ages it has taken to transform them to
+coal. A thin section of coal shows under a magnifier the structure of
+the stems of the coal-forming plants. Moreover, the veins of coal
+preserve above or below them, in shales that were once deposits of mud,
+the branching trunks of trees, perfectly fossilized. There are no better
+proofs of the vegetable origin of coal than the lumps themselves. But
+they are plain to the naked eye, while the coal tells its story to the
+man with the microscope.</p>
+
+<p>The fossil remains of the plants that flourished when coal was forming
+are gigantic, compared with plants of the same families now living. We
+must conclude that the climate was tropical, the air very heavy with
+moisture, and charged much more heavily than it is now with carbonic
+acid gas.</p>
+
+<p>These conditions produced, in rapid succession, forests of tree ferns
+and horsetails and giant club mosses. These are the three types of
+plants out of which the coal was made. They were all rich in resin,
+which makes the coal burn readily. The ferns had stems as large as tree
+trunks. Some have been found that are eighteen inches in diameter. We
+know they are ferns, because the leaves are found with their fruits
+attached to them in the manner of present-day ferns. The stems show the
+well<span class='pagenum'><a name="Page_164" id="Page_164">[Pg 164]</a></span> known scar by which fern leaves are joined. And the wood of these
+fossil fern stems is tubular in structure, just as the wood of living
+ferns is to-day.</p>
+
+<p>Among the ferns which dominated these old marsh forests grew one kind,
+the scaly leaves of which covered the stems and bore their fruits on the
+branching tips. These giants, some of them with trunks four feet in
+diameter, belong to the same group of plants as our creeping club
+mosses, but in the ancient days they stood up among the other ferns as
+trees forty or fifty feet high.</p>
+
+<p>The giant scouring rushes, or horsetails, had the same general
+characteristics as the little reed-like plants we know by those names
+to-day.</p>
+
+<p>The highest plants of the coal period were leafy trees with nut-like
+fruits, that resemble the yew trees of the present. These gigantic trees
+were the first conifers upon the earth. They foreshadowed the pines and
+the other cone-bearing evergreens. Their leaves were broad and their
+fruits nut-like. The Japanese ginkgo, or maidenhair fern tree, is an
+old-fashioned conifer somewhat like those first examples of this family.
+Trunks sixty to seventy feet long, crowned with broad leaves and a spike
+of fruit, have been found lying in the upper layers of the coal-seams,
+and in sandstone strata that lie between the strata of coal. Peculiar
+circular discs, which the microscope reveals along the sides of the wood
+fibres of these fossil trees, prove the wood structure to be like that
+of modern conifers.<span class='pagenum'><a name="Page_165" id="Page_165">[Pg 165]</a></span></p>
+
+<p>Generation after generation of forests lived and died in the vast
+spreading swamps of this era. The land sank, and freshets came here and
+there, drowning out all plant life, and covering the layers of peat with
+beds of sand or mud. When the water went down, other forests took
+possession, and a new coal-bed was started. It is plainly seen that
+flooding often put an end to coal formation. Fifteen seams of coal, one
+above another, is the greatest number that have been found. The veins
+vary from one inch to forty feet in thickness. These are separated by
+layers of sandstone or shale, which accumulated as sediment, covering
+the stumps of dead tree ferns and other growths, and preserving them as
+fossils to tell the story of those bygone ages as plainly as any other
+record could have done.</p>
+
+<p>Fresh-water animals succeeded those of salt water in the swamps that
+formed the coal measures. Overhead, the first insects flitted among the
+branches of the tree ferns. Dragon-flies darted above the surface and
+dipped in water as they do to-day. Spiders, scorpions, and cockroaches,
+all air-breathing insects, were represented, but none of the higher,
+nectar-loving insects, like flies and bees and butterflies, were there.
+Flowering plants had not yet appeared on the earth. Snakelike
+amphibians, some fishlike, some lizard-like, and huge crocodilian forms
+appeared for the first time. These air-breathing swamp-dwellers could
+not have lived in salt water.</p>
+
+<p>Fresh-water molluscs and land shells appear for<span class='pagenum'><a name="Page_166" id="Page_166">[Pg 166]</a></span> the first time as
+fossils in the rocks of the coal measures. On the shores of the ocean,
+the rocks of this period show that trilobites, horseshoe crabs, and
+fishes still lived in vast numbers, and corals continued to form
+limestone. The old types of marine animals changed gradually, but the
+coal measures show strikingly different fossils. These rocks bear the
+first record of fresh-water and land animals.<span class='pagenum'><a name="Page_167" id="Page_167">[Pg 167]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_MOST_USEFUL_METAL" id="THE_MOST_USEFUL_METAL"></a>THE MOST USEFUL METAL</h2>
+
+
+<p>It is fortunate for us all that, out of the half-dozen so-called useful
+metals, iron, which is the most useful of them all to the human race,
+should be also the most plentiful and the cheapest. Aluminum is abundant
+in the common clay and soil under our feet. But separating it is still
+an expensive process; so that this metal is not commercially so
+plentiful as iron is, nor is it cheap.</p>
+
+<p>All we know of the earth's substance is based on studies of the
+superficial part of its crust, a mere film compared with the eight
+thousand miles of its diameter. Nobody knows what the core of the
+earth&mdash;the great globe under this surface film&mdash;is made of; but we know
+that it is of heavier material than the surface layer; and geologists
+believe that iron is an important element in the central mass of the
+globe.</p>
+
+<p>One thing that makes this guess seem reasonable is the great abundance
+of iron in the earth's crust. Another thing is that meteors which fall
+on the earth out of the sky prove to be chiefly composed of iron. All of
+their other elements are ones which are found in our own rocks. If we
+believe that the earth itself is a fragment of the sun, thrown off in a
+heated<span class='pagenum'><a name="Page_168" id="Page_168">[Pg 168]</a></span> condition and cooling as it flew through space, we may consider
+it a giant meteor, made of the substances we find in the chance meteor
+that strikes the earth.</p>
+
+<p>Iron is found, not only in the soil, but in all plant and animal bodies
+that take their food from the soil. The red colour in fruits and
+flowers, and in the blood of the higher animals, is a form in which iron
+is familiar to us. It does more, perhaps, to make the world beautiful
+than any other mineral element known.</p>
+
+<p>But long before these benefits were understood, iron was the backbone of
+civilization. It is so to-day. Iron, transformed by a simple process
+into steel, sustains the commercial supremacy of the great civilized
+nations of the world. The railroad train, the steel-armoured battleship,
+the great bridge, the towering sky-scraper, the keen-edged tool, the
+delicate mechanism of watches and a thousand other scientific
+instruments&mdash;all these things are possible to-day because iron was
+discovered and has been put to use.</p>
+
+<p>It was probably one of the cave men, poking about in his fire among the
+rocks, who discovered a lump of molten metal which the heat had
+separated from the rest of the rocks. He examined this "clinker" after
+it cooled, and it interested him. It was a new discovery. It may have
+been he, or possibly his descendants, who learned that this metal could
+be pounded into other shapes, and freed by pounding<span class='pagenum'><a name="Page_169" id="Page_169">[Pg 169]</a></span> from the pebbles
+and other impurities that clung to it when it cooled. The relics of
+iron-tipped spears and arrows show the skill and ingenuity of our early
+ancestors in making use of iron as a means of killing their prey. The
+earliest remains of this kind have probably been lost because the iron
+rusted away.</p>
+
+<p>Man was pretty well along on the road to civilization before he learned
+where iron could be found in beds, and how it could be purified for his
+use. We now know that certain very minute plants, which live in quiet
+water, cause iron brought into that water to be precipitated, and to
+accumulate in the bottom of these boggy pools. In ancient days these bog
+deposits of iron often alternated with coal layers. Millions of years
+have passed since these two useful substances were laid down. To-day the
+coal is dug, along with the bog iron. The coal is burned to melt the
+iron ore and prepare it for use. It is a fortunate region that produces
+both coal and iron.</p>
+
+<p>Bituminous coal is plentiful, and scattered all over the country, while
+anthracite is scarce. The cheapest iron is made in Alabama, which has
+its ore in rich deposits in hillsides, and coal measures close by,
+furnishing the raw material for coke. The result is that the region of
+Birmingham has become the centre of great wealth through the development
+of iron and coal mines.</p>
+
+<p>Where water flows over limestone rock, and percolates through layers of
+this very common mineral,<span class='pagenum'><a name="Page_170" id="Page_170">[Pg 170]</a></span> it causes the iron, gathered in these rock
+masses, to be deposited in pockets. All along the Appalachian Mountains
+the iron has been gathered in beds which are being mined. These beds of
+ore are usually mixed with clay and other earthy substances from which
+the metal can be separated only by melting. The ore is thrown into a
+furnace where the metal melts and trickles down, leaving behind the
+non-metallic impurities. It is drawn off and run into moulds, where it
+cools in the form of "pig" iron.</p>
+
+<p>The first fuel used in the making of pig iron from the ore was charcoal.
+In America the early settlers had no difficulty in finding plenty of
+wood. Indeed, the forests were weeds that had to be cut down and burned
+to make room for fields of grain. The finding of iron ore always started
+a small industry in a colony. If there was a blacksmith, or any one else
+among the small company who understood working in iron, he was put in
+charge.</p>
+
+<p>To make the charcoal, wood was cut and piled closely in a dome-shaped
+heap, which was tightly covered with sods, except for a small opening
+near the ground. In this a fire was built, and smothered, but kept going
+until all the wood within the oven was charred.</p>
+
+<p>This fuel burned readily, with an intense heat, and without ashes.
+Sticks of charcoal have the form of the wood, and they are stiff enough
+to hold up the ore of iron so that it cannot crush out the fire. For a
+long time American iron was supplied by little<span class='pagenum'><a name="Page_171" id="Page_171">[Pg 171]</a></span> smelters, scattered here
+and there. The workmen beat the melted metal on the forge, freeing it
+from impurities, and shaping the pure metal into useful articles.
+Sometimes they made it into steel, by a process learned in the Old
+World.</p>
+
+<p>The American iron industry, which now is one of the greatest in the
+world, centres in Pittsburg, near which great deposits of iron and coal
+lie close together. The making of coke from coal has replaced the
+burning of charcoal for fuel. When the forests were cut away by
+lumbermen, the supply of charcoal threatened to give out, and
+experiments were made in charring coal, which resulted in the successful
+making of coke, a fuel made from coal by a process similar to the making
+of charcoal from wood. The story of the making of coke out of hard and
+soft coal is a long one, for it began as far back as the beginning of
+the nineteenth century.</p>
+
+<p>In 1812 the first boat-load of anthracite coal was sent to Philadelphia
+from a little settlement along the Lehigh River. A mine had been opened,
+the owner of which believed that the black, shiny "rocks" would burn.
+His neighbours laughed at him, for they had tried building fires with
+them, and concluded that it could not be done. In Philadelphia, the
+owners of some coke furnaces gave the new fuel a trial, in spite of the
+disgust of the stokers, who thought they were putting out their fires
+with a pile of stones. After a little, however, the new fuel began to
+burn with the peculiar pale flame and intense<span class='pagenum'><a name="Page_172" id="Page_172">[Pg 172]</a></span> heat that we know so
+well, and the stokers were convinced that here was a new fuel, with
+possibilities in it.</p>
+
+<p>But it was hard for people to be patient with the slow starting of this
+hard coal. Not until 1840 did it come into general favour, following the
+discovery that if hot air was supplied at the draught, instead of cold,
+anthracite coal became a perfect fuel.</p>
+
+<p>At Connellsville, Pennsylvania, a vein of coal was discovered which made
+coke of the very finest quality. Around this remarkable centre, coke
+ovens were built, and iron ore was shipped in, even from the rich beds
+of the Lake Superior country. But it was plain to see that Connellsville
+coal would become exhausted; and so experiments in coke-making from
+other coals were still made. When soft coal burns, a waxy tar oozes out
+of it, which tends to smother the fire. Early experiments with coal in
+melting iron ore indicated that soft coal was useless as a substitute
+for charcoal and coke; but later experiments proved that coke of fine
+quality can be made out of this bituminous soft coal, by drawing off the
+tar which makes the trouble. New processes were invented by which
+valuable gas and coal tar are taken out of bituminous coal, leaving, as
+a residue, coke that is equal in quality to that made from the
+Connellsville coal. Fortunes have been made out of the separation of the
+elements of the once despised soft coal. For the coke and each of its
+by-products, coal tar and coal gas, are commercial necessities of life.<span class='pagenum'><a name="Page_173" id="Page_173">[Pg 173]</a></span></p>
+
+<p>The impurities absorbed by the melting iron ore include carbon,
+phosphorus, and silicon. Carbon is the chief cause of the brittleness of
+cast iron. The puddling furnace was invented to remove this trouble. The
+melted ore was stirred on a broad, basin-like hearth, with a
+long-handled puddling rake. The flames swept over the surface, burning
+the carbon liberated by the stirring. It was a hard, hot job for the man
+at the rake, but it produced forge iron, that could be shaped, hot or
+cold, on the anvil.</p>
+
+<p>The next improvement was the process of pressing the hot iron between
+grooved rollers to rid it of slag and other foreign matters collected in
+the furnace. The old way was to hammer the metal free from such
+impurities. This was slow and hard work.</p>
+
+<p>Iron was an expensive and scarce metal until the hot blast-furnace
+cheapened the process of smelting the ore. The puddling furnace and the
+grooved rollers did still more to bring it into general use. The
+railroads developed with the iron industry. Soon they required a metal
+stronger than iron. Steel was far too expensive, though it was just what
+was needed. Efforts were made to find a cheap way to change iron into
+steel. Sir Henry Bessemer solved the problem by inventing the Bessemer
+converter. It is a great closed retort, which is filled with melted pig
+iron. A draught admits air, and the carbon is all burned out. Then a
+definite amount of carbon, just the amount required<span class='pagenum'><a name="Page_174" id="Page_174">[Pg 174]</a></span> to change iron into
+steel, is added, by throwing in bars of an alloy of carbon and
+manganese. The latter gives steel its toughness, and enables it to
+resist greater heat without crystallizing and thus losing its temper.</p>
+
+<p>When the carbon has been put in, the retort is closed. The molten metal
+absorbs the alloy, and the product is Bessemer steel. In fifteen minutes
+pig iron can be transformed into ingot steel. The invention made
+possible the use of steel in the construction of bridges, high
+buildings, and ships. It made this age of the world the Age of Steel.<span class='pagenum'><a name="Page_175" id="Page_175">[Pg 175]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_AGE_OF_REPTILES" id="THE_AGE_OF_REPTILES"></a>THE AGE OF REPTILES</h2>
+
+
+<p>Two big and interesting reptiles we see in the Zoo, the crocodile and
+its cousin, the alligator. In the everglades of Florida both are found.
+The crocodile of the Nile is protected by popular superstition, so it is
+in better luck than ours. The alligators have been killed off for their
+skins, and it is only a matter of time till these lumbering creatures
+will be found only in places where they are protected as the remnants of
+a vanished race. Giant reptiles of other kinds are few upon the earth
+now. The <i>boa constrictor</i> is the giant among snakes. The great tropical
+turtles represent an allied group. Most of the turtles, lizards, and
+snakes are small, and in no sense dominant over other creatures.</p>
+
+<p>The rocks that lie among the coal measures contain fossils of huge
+animals that lived in fresh water and on land, the ancestors of our
+frogs, toads, and salamanders, a group we call amphibians. Some of these
+animals had the form of snakes; some were fishlike, with scaly bodies;
+others were lizard-like or like huge crocodiles. These were the
+ancestors of the reptiles, which became the rulers of land and sea
+during the Mesozoic Era. The rocks that overlie<span class='pagenum'><a name="Page_176" id="Page_176">[Pg 176]</a></span> the coal measures
+contain fossils of these gigantic animals.</p>
+
+<p>Strange crocodile-like reptiles, with turtle-like beaks and tusks, but
+no teeth, left their skeletons in the mud of the shores they frequented.
+And others had teeth in groups&mdash;grinders, tearers, and cutters&mdash;like
+mammals. These had other traits like the old-fashioned, egg-laying
+mammals, the duck-billed platypus, for example, that is still found in
+Australia. Along with the remains of these creatures are found small
+pouched mammals, of the kangaroo kind, in the rocks of Europe and
+America. These land animals saw squatty cycads, and cone-bearing trees,
+the ancestors of our evergreens, growing in forests, and marshes covered
+with luxuriant growths of tree ferns and horsetails, the fallen bodies
+of which formed the recent coal that is now dug in Virginia and North
+Carolina. Ammonites, giant sea snails, with chambered shells that
+reached a yard and more in diameter, and gigantic squids, swam the seas.
+Sea urchins, starfish, and oysters were abundant. Insects flitted
+through the air, but no birds appeared among the trees or beasts in the
+jungles. Over all forms of living creatures reptiles ruled. They were
+remarkable in size and numbers. There were swimming, running, and flying
+forms.</p>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus176a_th.jpg" width="500" height="438" alt="Banded sandstone from Calico Ca&ntilde;on, South Dakota" title="" />
+<span class="caption">Banded sandstone from Calico Ca&ntilde;on, South Dakota</span>
+</div>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus176b_th.jpg" width="500" height="392" alt="By permission of the American Museum of Natural History
+
+Opalized wood from Utah" title="" />
+<span class="caption">By permission of the American Museum of Natural History<br />
+Opalized wood from Utah</span>
+</div>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus177_th.jpg" width="500" height="305" alt="By permission of the American Museum of Natural History
+
+Restoration of a carnivorous Dinosaur, Allosaurus, from the Upper
+Jurassic and Lower Cretaceous of Wyoming. When erect the animal was
+about 15 feet high" title="" />
+<span class="caption">By permission of the American Museum of Natural History<br />
+Restoration of a carnivorous Dinosaur, Allosaurus, from the Upper
+Jurassic and Lower Cretaceous of Wyoming. When erect the animal was
+about 15 feet high</span>
+</div><p><span class='pagenum'><a name="Page_177" id="Page_177">[Pg 177]</a></span></p>
+
+<p>The fish-reptile, <i>Ichthyosaurus</i>, was a hump-backed creature, thirty to
+forty feet long, with short neck, very large head, and long jaw, set
+with hundreds of pointed teeth. Its eye sockets were a foot across. The
+four short limbs were strong paddles, used for swimming. The long,
+slender tail ended in a flat fin. Perfect skeletons of this creature
+have been found. Its rival in the sea was the lizard-like
+<i>Plesiosaurus</i>, the small head of which was mounted on a long neck. The
+tail was short, but the paddles were long and powerful. No doubt this
+agile creature held its own, though somewhat smaller than the more
+massively built Ichthyosaurus.</p>
+
+<p>The land reptiles called <i>Dinosaurs</i> were the largest creatures that
+have ever walked the earth. In the American Museum of Natural History,
+in New York, the mounted skeleton of the giant Dinosaur fairly takes
+one's breath away. It is sixty-six feet long, and correspondingly large
+in every part, except its head. This massive creature was remarkably
+short of brains.</p>
+
+<p>The strangest thing about the land reptiles is the fact that certain of
+them walked on their hind legs, like birds, and made three-toed tracks
+in the mud. Indeed, these fossil tracks, found in slate, were called
+bird tracks, until the bones of the reptile skeleton with the bird-like
+foot were discovered. Certain long grooves in the slate, hitherto
+unexplained, were made by the long tail that dragged in the mud.</p>
+
+<p>When the mud dried, and was later covered with sediment of another kind,
+these prints were preserved, and when the bed of rock was discovered by
+quarrymen, the two kinds split apart, showing<span class='pagenum'><a name="Page_178" id="Page_178">[Pg 178]</a></span> the record of the stroll
+of a giant along the river bank in bygone days.</p>
+
+<p>The flying reptiles were still more bird-like in structure, though
+gigantic in size. Imagine the appearance of a great lizard with
+bat-like, webbed wings and bat-like, toothed jaws! The first feathered
+fossil bird was discovered in the limestone rock of Bavaria. It was a
+wonderfully preserved fossil, showing the feathers perfectly. Three
+fingers of each "hand" were free and clawed, so that the creature could
+seize its prey, and yet use its feathered wings in flight. The small
+head had jaws set with socketed teeth, like a reptile's, and the long,
+lizard tail of twenty-one bones had a pair of side feathers at each
+joint. This <i>Archeopteryx</i> is the reptilian ancestor of birds. During
+this age of the world, one branch of the reptile group established the
+family line of birds. The bird-like reptiles are the connecting link
+between the two races. How much both birds and reptiles have changed
+from that ancient type, their common ancestor!</p>
+
+<p>I have mentioned but a few of the types of animals that make the
+reptilian age the wonder of all time. One after another skeletons are
+unearthed and new species are found. The Connecticut River Valley, with
+its red sandstones and shales of the Mesozoic Era, is famous among
+geologists, because it preserves the tracks of reptiles, insects, and
+crustaceans. These signs tell much of the life that existed when these
+flakes of stone were sandy and muddy stretches Not many bones have been
+found, however. The thickness of these rocks is between one and two
+miles. The time required to accumulate so much sediment must have been
+very great.</p>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus178_th.jpg" width="500" height="292" alt="By permission of the American Museum of Natural History
+
+Model of a three-horned Dinosaur, Triceratops, from Cretaceous of
+Montana. Animal in life about 25 feet long" title="" />
+<span class="caption">By permission of the American Museum of Natural History<br />
+Model of a three-horned Dinosaur, Triceratops, from Cretaceous of
+Montana. Animal in life about 25 feet long</span>
+</div>
+
+<div class="figcenter" style="width: 332px;">
+<img src="images/illus179_th.jpg" width="332" height="500" alt="By permission of the American Museum of Natural History
+
+Mounting the forelegs of Brontosaurus, the aquatic Dinosaur" title="" />
+<span class="caption">By permission of the American Museum of Natural History<br />
+Mounting the forelegs of Brontosaurus, the aquatic Dinosaur</span>
+</div><p><span class='pagenum'><a name="Page_179" id="Page_179">[Pg 179]</a></span></p>
+
+<p>It is not clear just what caused the race of giant reptiles to decline
+and pass away. The climate did not materially change. Perhaps races grow
+old, and ripe for death, after living long on the earth. It seems as if
+their time was up; and the clumsy giants abdicated their reign, leaving
+dominion over the sea, the air, and the land to those animals adapted to
+take the places they were obliged to vacate.<span class='pagenum'><a name="Page_180" id="Page_180">[Pg 180]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_AGE_OF_MAMMALS" id="THE_AGE_OF_MAMMALS"></a>THE AGE OF MAMMALS</h2>
+
+
+<p>The warm-blooded birds and mammals followed the reptiles. This does not
+mean that all reptiles died, after having ruled the earth for thousands
+of years. It means that changes in climate and other life conditions
+were unfavourable to the giants of the cold-blooded races, and gradually
+they passed away. They are represented now on the earth by lesser
+reptiles, which live comfortably with the wild creatures of other
+tribes, but which in no sense rule in the brute creation. They live
+rather a lurking, cautious life, and have to hide from enemies, except a
+few more able kinds, provided with means of defense.</p>
+
+<p>There were mammals on the earth in the days of reptilian supremacy, but
+they were small in size and numbers, and had to avoid any open conflict
+with the giant reptiles, or be worsted in a fight. Now the time came
+when the ruling power changed hands. The mammals had their turn at
+ruling the lower animals. It was the beginning of things as they are
+to-day, for mammals still rule. But many millions of years have probably
+stood between the age when this group of animals first began to swarm
+over the earth,<span class='pagenum'><a name="Page_181" id="Page_181">[Pg 181]</a></span> and the time when Man came to be ruler over all created
+things.</p>
+
+<p>Among the reptiles of the period when the sea, the land, and the air
+were swarming with these great creatures were certain kinds that had
+traits of mammals. Others were bird-like. From these reptilian ancestors
+birds and mammals have sprung. No one doubts this. The fossils prove it,
+step by step.</p>
+
+<p>Yet the rocks surprise the geologist with the suddenness with which many
+new kinds of mammals appeared on the earth. Possibly the rocks
+containing the bones of so many kinds were fortunately located. The
+spots may have been morasses where migrating mammals were overwhelmed
+while passing. Possibly conditions favored the rapid development of new
+kinds, and the multiplication of their numbers. Warm, moist climate
+furnished abundant succulent plant food for the herbivors, and these in
+turn furnished prey for the carnivors.</p>
+
+<p>The coal formed during the Tertiary Period gives added proof that the
+plant life was luxuriant. The kinds of trees that grew far north of our
+present warm zones have left in the rocks evidence in the form of
+perfect leaves and cones and other fruits. For instance, magnolias grew
+in Greenland, and palm trees in Dakota. The temperature of Greenland was
+thirty degrees warmer than it is now. Our Northern States lie in a belt
+that must have had a climate much like that of Florida now. Europe was
+correspondingly mild.<span class='pagenum'><a name="Page_182" id="Page_182">[Pg 182]</a></span></p>
+
+<p>A special chapter tells of the gradual development of the horse. One
+hundred different kinds of mammals have been found in the Eocene rocks,
+many of which have representative species at the same time in Europe and
+America. The rocks of Asia probably have similar records.</p>
+
+<p>The Eocene rocks, lowest of the Tertiary strata, contain remains of
+animals the families of which are now extinct. Next overlying the
+Eocene, the Miocene rocks have fossils of animals belonging to modern
+families&mdash;rhinoceroses, camels, deer, dogs, cats, horses&mdash;but the genera
+of which are now extinct. The Pliocene strata (above the Miocene)
+contains fossils of animals so closely related to the wild animals now
+on the earth as to belong to the same genera. They differ from modern
+kinds only in the species, as the red squirrel is a different species
+from the gray.</p>
+
+<p>So the record in the rocks shows a gradual approach of the mammals to
+the kinds we know, a gradual passing of the mighty forms that ruled by
+size and strength, and the coming of forms with greater intelligence,
+adapted to the change to a colder climate.</p>
+
+<p>It sometimes happens that a farmer, digging a well on the prairie,
+strikes the skeleton of a monster mammal, called the <i>mastodon</i>. This
+very thing happened on a neighbour's farm when I was a girl, in Iowa.
+Everybody was excited. The owner of the land dug out every bone, careful
+that the whole skeleton be found. As he expected, the director of a
+museum was glad to pay a high price for the bones.</p>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus182_th.jpg" width="500" height="316" alt="By permission of the American Museum of Natural History
+
+Restoration of an aquatic Dinosaur, Brontosaurus excelsus, from the
+Upper Jurassic and Lower Cretaceous of Wyoming. The animal in life was
+over 60 feet long" title="" />
+<span class="caption">By permission of the American Museum of Natural History<br />
+Restoration of an aquatic Dinosaur, Brontosaurus excelsus, from the
+Upper Jurassic and Lower Cretaceous of Wyoming. The animal in life was
+over 60 feet long</span>
+</div>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus183_th.jpg" width="500" height="308" alt="By permission of the American Museum of Natural History
+
+Restoration of the small carnivorous Dinosaur, Ornitholestes hermanui,
+catching a primitive bird Arch&aelig;opteryx. Upper Jurassic and Lower
+Cretaceous" title="" />
+<span class="caption">By permission of the American Museum of Natural History<br />
+Restoration of the small carnivorous Dinosaur, Ornitholestes hermanui,
+catching a primitive bird Arch&aelig;opteryx. Upper Jurassic and Lower
+Cretaceous</span>
+</div><p><span class='pagenum'><a name="Page_183" id="Page_183">[Pg 183]</a></span></p>
+
+<p>The mastodon was about the size of an elephant, with massive limbs, and
+large, heavy head that bore two stout, up-curved tusks of ivory. The
+creature moved in herds like the buffalo from swamp to swamp; and old
+age coming on, the individual, unable to keep up with the herd, sank to
+his death in the boggy ground. The peat accumulated over his bones,
+undisturbed until thousands of years elapse, and the chance digging of a
+well discovers his skeleton.</p>
+
+<p>Frozen in the ice of northern Siberia, near the mouths of rivers, a
+number of mammoths have been found. These are creatures of the elephant
+family, and belonging to the extinct race that lived in the Quaternary
+Period, just succeeding the Tertiary. The ice overtook the specimens,
+and they have been in cold storage ever since. For this reason, both
+flesh and bones are preserved, a rare thing to happen, and rarer still
+to be seen by a scientist.</p>
+
+<p>The ignorant natives made a business of watching the ice masses at the
+river mouth for dark spots that showed where a mammoth was encased in
+the ice. If an iceberg broke off near such a place, the sun might thaw
+the ice front of the glacier, until the hairy monster could at length be
+reached. His long hair served for many uses, and the wool that grew
+under the hair was used as a protection from the<span class='pagenum'><a name="Page_184" id="Page_184">[Pg 184]</a></span> Arctic winter. The
+frozen flesh was eaten; the bones carved into useful tools; but the
+chief value of the find was in the great tusks of ivory, that curved
+forward and pointed over the huge shoulders. It was worth a fortune to
+get a pair and sell them to a buyer from St. Petersburg.</p>
+
+<p>One of the finest museum specimens of the mammoth was secured by buying
+the tusks of the dealer, and by his aid tracing the location of the
+carcass, which was found still intact, except that dogs had eaten away
+part of one foreleg, bone and all. From this carefully preserved
+specimen, models have been made, exactly copying the shape and the size
+of the animal, its skin, hair, and other details.</p>
+
+<p>The sabre-toothed tiger, the sharp tusks of which, six to eight inches
+long, made it a far more ferocious beast than any modern tiger of
+tropical jungles, was a Quaternary inhabitant of Europe and America. So
+was a smaller tiger, and a lion. The Irish elk, which stood eleven feet
+high, with antlers that spread ten feet apart at the tips, was monarch
+in the deer family, which had several different species on both
+continents. Wild horses and wild cattle, one or two of great size,
+roamed the woods, while rhinos and the hippopotamus kept near the
+water-courses. Hyenas skulked in the shadows, and acted as scavengers
+where the great beasts of prey had feasted. Sloths and cuirassed
+animals, like giant armadillos, lived in America. Among bears was one,
+the cave bear, larger than the grizzly. True monkeys<span class='pagenum'><a name="Page_185" id="Page_185">[Pg 185]</a></span> climbed the trees.
+Flamingo, parrots, and tall secretary birds followed the giant
+<i>gastornis</i>, the ancestor of wading birds and ostriches, which stood ten
+feet high, but had wings as small and useless as the auk of later times.</p>
+
+<p>With the entrance of the modern types of trees, came other flowering
+plants, and with them the insects that live on the nectar of flowers.
+Through a long line of primitive forms, now extinct, flowering plants
+and their insect friends conform to modern types. The record is written
+in the great stone book.</p>
+
+<p>The Age of Mammals in America and Europe ended with the gradual rise of
+the continental areas, and a fall of temperature that ushered in the Ice
+Age. With the death of tropical vegetation, the giant mammals passed
+away.<span class='pagenum'><a name="Page_186" id="Page_186">[Pg 186]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_HORSE_AND_HIS_ANCESTORS" id="THE_HORSE_AND_HIS_ANCESTORS"></a>THE HORSE AND HIS ANCESTORS</h2>
+
+
+<p>Every city has a horse market, where you may look over hundreds of
+animals and select one of any colour, size, or kind. The least in size
+and weight is the Shetland pony, which one man buys for his children to
+drive or ride. Another man wants a long-legged, deep-chested hunter.
+Another wants heavy draught-horses, with legs like great pillars under
+them, and thick, muscular necks&mdash;horses weighing nearly a ton apiece and
+able to draw the heaviest trucks. What a contrast between these slow but
+powerful animals and the graceful, prancing racer with legs like
+pipe-stems&mdash;fleet and agile, but not strong enough to draw a heavy load!</p>
+
+<p>All these different breeds of horses have been developed since man
+succeeded in capturing the wild horse and making it help him. Man
+himself was still a savage, and he had to fight with wild beasts, as if
+he were one of them, until he discovered that he could conquer them by
+some power higher than physical strength. From this point on, human
+intelligence has been the power that rules the lower animals. Its
+gradual development is the story of the advance of civilization on the
+earth. Through unknown thousands of years it has gone on, and it is not
+yet finished.</p>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus186_th.jpg" width="500" height="300" alt="By permission of the American Museum of Natural History
+
+Restoration of a Siberian mammoth, Elephas primogenius, pursued by men
+of the old stone age of Europe. Late Pleistocene epoch" title="" />
+<span class="caption">By permission of the American Museum of Natural History<br />
+Restoration of a Siberian mammoth, Elephas primogenius, pursued by men
+of the old stone age of Europe. Late Pleistocene epoch</span>
+</div>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus187_th.jpg" width="500" height="314" alt="By permission of the American Museum of Natural History
+
+Restoration of a small four-toed ancestor of the horse family, Eohippus
+venticolus. Lower Eocene of Wyoming" title="" />
+<span class="caption">By permission of the American Museum of Natural History<br />
+Restoration of a small four-toed ancestor of the horse family, Eohippus
+venticolus. Lower Eocene of Wyoming</span>
+</div><p><span class='pagenum'><a name="Page_187" id="Page_187">[Pg 187]</a></span></p>
+
+<p>Just when and where and how our savage ancestors succeeded in taming the
+wild horse of the plains and the forests of Europe or Asia is unknown.
+Man first made friends with the wild sheep, which were probably more
+docile than wild oxen and horses. We can imagine cold and hungry men
+seeking shelter from storms in rocky hollows, where sheep were huddled.
+How warm the woolly coats of these animals felt to their human
+fellow-creatures crowded in with them in the dark!</p>
+
+<p>It is believed that the primitive men who used stone axes as implements
+and weapons, learned to use horses to aid them in their hunting, and in
+their warfare with beasts and other men. Gradually these useful animals
+were adapted to different uses; and at length different breeds were
+evolved. Climate and food supply had much to do with the size and the
+character of the breeds. In the Shetland Islands the animals are
+naturally dwarfed by the cold, bleak winters, and the scant vegetation
+on which they subsist. In middle Europe, where the summers are long and
+the winters mild, vegetation is luxurious, and the early horses
+developed large frames and heavy muscles. The Shetland pony and the
+Percheron draught-horse are the two extremes of size.</p>
+
+<p>What man has done in changing the types of horses is to emphasize
+natural differences. The offspring of the early heavy horses became
+heavier than their<span class='pagenum'><a name="Page_188" id="Page_188">[Pg 188]</a></span> parents. The present draught-horse was produced,
+after many generations, all of which gradually approached the type
+desired. The slender racehorses, bred for speed and endurance rather
+than strength, are the offspring of generations of parents that had
+these qualities strongly marked. Hence came the English thoroughbred and
+the American trotter.</p>
+
+<p>We can read in books the history of breeds of horses. Our knowledge of
+what horses were like in prehistoric times is scant. It is written in
+layers of rock that are not very deep, but are uncovered only here and
+there, and only now and then seen by eyes that can read the story told
+by fossil skeletons of horses of the ages long past.</p>
+
+<p>Geologists have unearthed from time to time skeletons of horses. It was
+Professor Marsh who spent so much time in studying the wonderful beds of
+fossil mammals in the western part of this country, and found among them
+the skeletons of many species of horses that lived here with camels and
+elephants and rhinoceroses and tigers, long before the time of man's
+coming.</p>
+
+<p>How can any one know that these bones belonged to a horse's skeleton?
+Because some of them are like the bones of a modern horse. It is an easy
+matter for a student of animal anatomy to distinguish a horse from a cow
+by its bones. The teeth and the foot are enough. These are important and
+distinguishing characters. It is by peculiarities in the formation of
+the bones of the foot that the<span class='pagenum'><a name="Page_189" id="Page_189">[Pg 189]</a></span> different species of extinct horses are
+recognized by geologists.</p>
+
+<p>Wild horses still exist in the wilds of Russia. Remains of the same
+species have been dug out of the soil and found in caves in rocky
+regions. Deeper in the earth are found the bones of horses differing
+from those now living. The bones of the foot indicate a different kind
+of horse&mdash;an unknown species. But in the main features, the skeleton is
+distinctly horse-like.</p>
+
+<p>In rocks of deeper strata the fossil bones of other horses are found.
+They differ somewhat from those found in rocks nearer the surface of the
+earth, and still more from those of the modern horse. The older the
+rocks, the more the fossil horse differs from the modern. Could you
+think of a more interesting adventure than to find the oldest rocks that
+show the skeletons of horses?</p>
+
+<p>The foot of a horse is a long one, though we think of it as merely the
+part he walks on. A horse walks on the end of his one toe. The nail of
+the toe we call the "hoof." The true heel is the hock, a sharp joint
+like an elbow nearly half way up the leg. Along each side of the cannon,
+the long bone of this foot, lies a splint of bone, which is the remnant
+of a toe, that is gradually being obliterated from the skeleton. These
+two splints in the modern horse's foot tell the last chapter of an
+interesting story. The earliest American horse, the existence of which
+is proved by fossil bones, tells the first chapter. The<span class='pagenum'><a name="Page_190" id="Page_190">[Pg 190]</a></span> story has been
+read backward by geologists. It is told by a series of skeletons, found
+in successive strata of rock.</p>
+
+<p>The "Bad Lands" of the arid Western States are rich in fossil remains of
+horses. Below the surface soil lie the rocks of the Quaternary Period,
+which included the drift laid down by the receding glaciers and the
+floods that followed the melting of the ice-sheet. Under the Quaternary
+lie the Tertiary rocks. These comprise three series, called the Eocene,
+Miocene, and Pliocene, the Eocene being the oldest. In the middle region
+of North America, ponds and marshy tracts were filled in during the
+Tertiary Period, by sediment from rivers; and in these beds of clay and
+other rock d&eacute;bris the remains of fresh-water and land animals are
+preserved. Raised out of water, and exposed to erosive action of wind
+and water, these deposits are easily worn away, for they have not the
+solidity of older rocks. They are the crumbly Bad Lands of the West, cut
+through by rivers, and strangely sculptured by wind and rain. Here the
+fossil horses have been found.</p>
+
+<p><i>Eohippus</i>, the dawn horse, is the name given a skeleton found in 1880
+in the lower Eocene strata in Wyoming. This specimen lay buried in a
+rock formation ages older than that in which the oldest known skeleton
+of this family had been found. Its discovery made a great sensation
+among scientists. This little animal, the skeleton of which is no larger
+than that of a fox, had four perfect toes, and a fifth<span class='pagenum'><a name="Page_191" id="Page_191">[Pg 191]</a></span> splint on the
+forefoot, and three toes on the hind foot. The teeth are herbivorous.</p>
+
+<p><i>Orohippus</i>, with a larger skeleton, was found in the middle Eocene
+strata of Wyoming. Its feet are like those of its predecessor, except
+that the splint is gone. The teeth as well as the feet are more like
+those of the modern horse.</p>
+
+<p><i>Mesohippus</i>, the three-toed horse, found in the Miocene, shows the
+fourth toe reduced to splints, and the skeleton as big as that of a
+sheep. In this the horse family becomes fairly established.</p>
+
+<p><i>Hypohippus</i>, the three-toed forest horse, found in the middle Miocene
+strata of Colorado, is a related species, but not a direct ancestor of
+the modern horse.</p>
+
+<p><i>Neohipparion</i>, the three-toed desert horse, from the upper Miocene
+strata, shows the three toes still present. But the Pliocene rocks
+contain fossils showing gradual reduction of the two side toes,
+modification of the teeth, and increase in size of the skeleton.</p>
+
+<p><i>Protohippus</i> and <i>Pliohippus</i>, the one-toed species from the Pliocene
+strata, illustrate these changes. They were about the size of small
+ponies.</p>
+
+<p><i>Equus</i>, the modern horse, was represented in the Pliocene strata by a
+species, now extinct, called <i>Equus Scotti</i>. This we may regard as the
+true wild horse of America, for it was as large as the domesticated
+horse, and much like it, though more like a zebra in some respects. No
+one can tell why<span class='pagenum'><a name="Page_192" id="Page_192">[Pg 192]</a></span> these animals, once abundant in this country, became
+extinct at the end of the Tertiary Period. But this is undoubtedly true.</p>
+
+<p>The types described form a series showing how the ancestors of the
+modern horse, grazing on the marshy borders of ancient ponds, lived and
+died, generation after generation, through a period covering thousands,
+possibly millions, of years. Along the sides of the crumbling buttes
+these ancient burying-grounds are being uncovered. Within a dozen years
+several expeditions, fitted out by the American Museum of Natural
+History, have searched the out-cropping strata in Dakota and Wyoming for
+bones of mammals known to have lived at the time the strata were forming
+in the muddy shallows along the margins of lake and marsh. Duplicate
+skeletons of the primitive horse types above have been found, and vast
+numbers of their scattered bones. Each summer geological excursions will
+add to the wealth of fossils of this family collected in museums.</p>
+
+<p>The Tertiary rocks in Europe yield the same kind of secrets. The region
+of Paris overlies the estuary of an ancient river. When the strata are
+laid bare by the digging of foundations for buildings, bones are found
+in abundance. Cuvier was a famous French geologist who made extensive
+studies of the remains of the prehistoric animals found in this old
+burial-place called by scientists the Paris basin. He believed that the
+dead bodies floated down-stream<span class='pagenum'><a name="Page_193" id="Page_193">[Pg 193]</a></span> and accumulated in the mud of the
+delta, where the tide checked the river's current.</p>
+
+<p>Skeletons of the Hipparion, a graceful, three-toed horse, were found in
+numbers in the strata of the Miocene time. This animal lived in Europe
+while the Pliohippus and the Protohippus were flourishing in America.</p>
+
+<p>A great number of species of tapir-like animals left their bones in the
+Paris basin, among them a three-hoofed animal which may have been the
+connecting link between the horse and the tapir families. Cuvier found
+the connecting link between tapirs and cud-chewing mammals.<span class='pagenum'><a name="Page_194" id="Page_194">[Pg 194]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_AGE_OF_MAN" id="THE_AGE_OF_MAN"></a>THE AGE OF MAN</h2>
+
+
+<p>The hairy, woolly mammoth was one of the giant mammals that withstood
+the cold of the great ice flood, when the less hardy kinds were cut off
+by the changing climate of the northern half of Europe and America. In
+caves where the wild animals took refuge from their enemies, skeletons
+of men have been found with those of the beasts. With these chance
+skeletons have been found rude, chipped stone spear-heads, hammers, and
+other tools. With these the savage ancestors of our race defended
+themselves, and preyed on such animals as they could use for food. They
+hunted the clumsy mammoth successfully, and shared the caverns in the
+rocks with animals like the hyena, the sabre-toothed tiger, and the cave
+bear, which made these places their homes. In California a human skull
+was found in the bed of an ancient river, which was buried by a lava
+flow from craters long ago extinct. With this buried skull a few
+well-shaped but rough stone tools were found. This man must have lived
+when the great ice flood was at its height.</p>
+
+<p>In southern France, caves have been opened that contained bones and
+implements of men who evidently lived by fishing and hunting. Bone
+fish-hooks<span class='pagenum'><a name="Page_195" id="Page_195">[Pg 195]</a></span> showed skill in carving with the sharp edges of flint
+flakes. A spirited drawing of a mammoth, made on a flat, stone surface,
+is a proof that savage instincts were less prominent in these cave men
+than in those who fought the great reindeer and the mammoth farther
+north.</p>
+
+<p>In later times men of higher intelligence formed tribes, tamed the wild
+horse, the ox, and the sheep, and made friends with the dog. Great heaps
+of shells along the shores show where the tribes assembled at certain
+times to feast on oysters and clams. Bones of animals used as food, and
+tools, are found in these heaps, called "kitchen-middens." These are
+especially numerous in Northern Europe. The stone implements used by
+these tribes were smoothly polished. A higher intelligence expressed
+itself also by the making of utensils out of clay. This pottery has been
+found in shell heaps. So the rude cave man, who was scarcely less a wild
+beast than the animals which competed with him for a living and a
+shelter from storms and cold, was succeeded by a higher man who brought
+the brutes into subjection by force of will and not by physical
+strength.</p>
+
+<p>The lake-dwellers, men of the Bronze Age, built houses on piles in the
+lakes of Central Europe. About sixty years ago the water was low, and
+these relics of a vanished race were first discovered. The lake bottoms
+were scraped for further evidences of their life. Tools of polished
+stone and of bronze were taken up in considerable numbers. Stored
+grains<span class='pagenum'><a name="Page_196" id="Page_196">[Pg 196]</a></span> and dried fruits of several kinds were found. Ornamental
+trinkets, weapons of hunters and warriors, and agricultural tools tell
+how the people lived. Their houses were probably built over the water as
+a means of safety from attack of beasts or hostile men.</p>
+
+<p>In our country the mound-builders have left the story of their manners
+of life in the spacious, many-roomed tribal houses, built underground,
+and left with a great variety of relics to the explorers of modern
+times. These people worked the copper mines, and hammered and polished
+lumps of pure metal into implements for many uses. With these are tools
+of polished stone. Stores of corn were found in many mounds scattered in
+the Mississippi Valley.</p>
+
+<p>The cliff-dwellers of the mesas of Arizona and New Mexico had habits
+like those of the mound-builders, and the Aztecs, a vanished race in the
+Southwest, at whose wealth and high civilization the invading Spaniards
+under Cortez marvelled. The plastered stone houses of the cliff-dwelling
+Indians had many stories and rooms, each built to house a tribe, not
+merely a family.</p>
+
+<p>The Pueblo, the Moqui, and the Zuni Indians build similar dwellings
+to-day, isolated on the tops of almost inaccessible mesas.</p>
+
+<p>Millions of years have passed since life appeared on the earth.
+Gradually higher forms have followed lower ones in the sea and on the
+land. But<span class='pagenum'><a name="Page_197" id="Page_197">[Pg 197]</a></span> not all of the lower forms have gone. All grades of plants
+and animals still flourish, but the dominant class in each age is more
+highly organized than the class that ruled the preceding age.</p>
+
+<p>To discover the earth's treasure, and to turn it to use; to tame wild
+animals and wild plants, and make them serve him; to create ever more
+beautiful and more useful forms in domestication; to find out the
+earth's life story, by reading the pages of the great stone book&mdash;these
+are undertakings that waited for man's coming.<span class='pagenum'><a name="Page_198" id="Page_198">[Pg 198]</a></span></p>
+
+<p><span class='pagenum'><a name="Page_199" id="Page_199">[Pg 199]</a></span></p><hr style='width: 45%;' />
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="PART_II" id="PART_II"></a>PART II</h2>
+
+<h3>THE SKY</h3>
+
+<p><span class='pagenum'><a name="Page_200" id="Page_200">[Pg 200]</a></span></p>
+<hr style='width: 45%;' />
+<p><span class='pagenum'><a name="Page_201" id="Page_201">[Pg 201]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="EVERY_FAMILY_A_STAR_CLUB" id="EVERY_FAMILY_A_STAR_CLUB"></a>EVERY FAMILY A "STAR CLUB"</h2>
+
+
+<p>The best family hobby we have ever had is the stars. We have a star club
+with no dues to pay, no officers to boss us, and only three rules:</p>
+
+<p>1. We shall have nothing but "fun" in this club&mdash;no hard work. Therefore
+no mathematics for us!</p>
+
+<p>2. We can't afford a telescope. Therefore we must be satisfied with what
+bright eyes can see.</p>
+
+<p>3. No second-hand wonders for us! We want to see the things ourselves,
+instead of depending on books.</p>
+
+<p>You can't imagine what pleasure we have had in one short year! The baby,
+of course, was too young to learn anything, and besides he was in bed
+long before the stars came out. But Ruth, our seven-year-old, knows ten
+of the fifteen brightest stars; and she can pick out twelve of the most
+beautiful groups or constellations. We grown-ups know all of the
+brightest stars, and all forty-eight of the most famous constellations.
+And the whole time we have given to it would not exceed ten minutes a
+day!</p>
+
+<p>And the best part is the <i>way</i> we know the stars. The sky is no longer
+bewildering to us. The stars are not cold, strange, mysterious. They are
+friends.<span class='pagenum'><a name="Page_202" id="Page_202">[Pg 202]</a></span> We know their faces just as easily as you know your playmates.
+For instance, we know Sirius, because he is the brightest. We know
+Castor and Pollux, because they are twins. We know Regulus, because he
+is in the handle of the Sickle. And some we know by their colours. They
+are just as different as President Taft, "Ty" Cobb, Horace Fletcher and
+Maude Adams. And quite as interesting!</p>
+
+<p>What's more, none of us can ever get lost again. No matter what strange
+woods or city we go to, we never get "turned around." Or if we do, we
+quickly find the right way by means of the sun or the stars.</p>
+
+<p>Then, too, our star club gives us all a little exercise when we need it
+most. Winter is the time when we all work hardest and have the fewest
+outdoor games. Winter is also the best time for young children to enjoy
+the stars, because it gets dark earlier in winter&mdash;by five o'clock, or
+long before children go to bed. It is pleasant to go out doors for half
+an hour before supper and learn one new star or constellation.</p>
+
+<p>Again, it is always entertaining because every night you find the old
+friends in new places. No two nights are just the same. The changes of
+the moon make a great difference. Some nights you enjoy the moonlight;
+other nights you wish there were no moon, because it keeps you from
+spying out some new star. We have a little magazine that tells us all
+the news of the stars and the planets and the comets <i>before</i> the things
+happen! We pay a dollar a year<span class='pagenum'><a name="Page_203" id="Page_203">[Pg 203]</a></span> for it. It is called the <i>Monthly
+Evening Sky Map</i>.</p>
+
+<p>When we first became enthusiastic about stars, the father of our family
+said: "Well, I think our Star Club will last about two years. I judge it
+will cost us about two dollars and we shall get about twenty dollars
+worth of fun out of it." But in all three respects father was mistaken.</p>
+
+<p>Part of the two dollars father spoke of went for a book called "The
+Friendly Stars," and seventy-five cents we spent for the most
+entertaining thing our family ever bought&mdash;a planisphere. This is a
+device which enables us to tell just where any star is, at any time, day
+or night, the whole year. It has a disc which revolves. All we have to
+do is to move it until the month and the day come right opposite the
+very hour we are looking at it, and then we can tell in a moment which
+stars can be seen at that time. Then we go down the street where there
+is a good electric light at the corner and we hold our planisphere up,
+almost straight overhead. The light shines through, so that we can read
+it, and it is just as if we had a map of the heavens. We can pick out
+all the interesting constellations and name them just as easily as we
+could find the Great Lakes or Rocky Mountains in our geography.</p>
+
+<p>We became so eager not to miss any good thing that father got another
+book. Every birthday in our family brought a new star book, until now we
+have about a dozen&mdash;all of them interesting and not one<span class='pagenum'><a name="Page_204" id="Page_204">[Pg 204]</a></span> of them having
+mathematics that children cannot understand. So I think we have spent on
+stars fifteen dollars more than we needed to spend (but I'm glad we did
+it), and I think we have had about two hundred dollars worth of fun!
+Yes, when I think what young people spend on ball games, fishing,
+tennis, skating, and all the other things that children love, I am sure
+our family has had about two hundred dollars worth of fun out of stars.
+And there is more to come!</p>
+
+<p>You would laugh to know why I enjoy stars so much. I have always studied
+birds and flowers and trees and rocks and shells so much that I was
+afraid to get interested in stars. I thought it wouldn't rest me. But
+it's a totally different kind of science from any I ever studied! There
+are no families, genera, and species among the stars, thank Heaven!
+That's one reason they refresh me. Another is that no one can press them
+and put them in a herbarium, or shoot them and put them in a museum. And
+another thing about them that brings balm to my spirit is that no human
+being can destroy their beauty. No one can "sub-divide" Capella and fill
+it with tenements. No one can use Vega for a bill-board. Ah, well! we
+must not be disturbed if every member of our family has a different
+point of view toward the stars; we can all enjoy and love them in our
+own ways.</p>
+
+<p>How would you like to start a Star Club like ours? You ought to be able
+to persuade your family to<span class='pagenum'><a name="Page_205" id="Page_205">[Pg 205]</a></span> form one, because it need not cost a cent.
+Perhaps this book will interest them all, but the better way is for you
+to read about one constellation and then go out with some of the family
+and find it. This book does not tell about wonderful things you can
+never see; it tells about the wonderful things all of us can see.</p>
+
+<p>I wish you success with your Star Club. Perhaps your uncles and aunts
+will start clubs, too. We have three Star Clubs in our family&mdash;one in
+New York, one in Michigan, and one in Colorado. Last winter the
+"Colorado Star Gazers" sent this challenge to the "New Jersey
+Night-Owls:" "<i>We bet you can't see Venus by daylight!</i>"</p>
+
+<p>That seemed possible, because during that week the "evening star" was by
+far the brightest object in the sky. But father and daughter searched
+the sky before sunset in vain, and finally we had to ask the "Moonstruck
+Michiganders" how to see Venus while the sun was shining. Back came
+these directions on a postal-card: "Wait until it is dark and any one
+can see Venus. Then find some tree, or other object, which is in line
+with Venus and over which you can just see her. Put a stake where you
+stand. Next day go there half an hour before sunset, and stand a little
+to the west. You will see Venus as big as life. The next afternoon you
+can find her by four o'clock. And if you keep on you will see her day
+before yesterday!"</p>
+
+<p>That was a great "stunt." We did it; and there<span class='pagenum'><a name="Page_206" id="Page_206">[Pg 206]</a></span> are dozens like it you
+can do. And that reminds me that father was mistaken about our interest
+lasting only two years. We know that it will not die till we do. For,
+even if we never get a telescope, there will always be new things to
+see. Our club has still to catch Algol, the "demon's eye," which goes
+out and gleams forth every three days, because it is obscured by some
+dark planet we can never see. And we have never yet seen Mira the
+wonderful, which for some mysterious reason dies down to ninth magnitude
+and then blazes up to second magnitude every eleventh month.</p>
+
+<p>Ah, yes, the wonders and the beauties of astronomy ever deepen and
+widen. Better make friends with the stars now. For when you are old
+there are no friends like old friends.<span class='pagenum'><a name="Page_207" id="Page_207">[Pg 207]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_DIPPERS_AND_THE_POLE_STAR" id="THE_DIPPERS_AND_THE_POLE_STAR"></a>THE DIPPERS AND THE POLE STAR</h2>
+
+
+<p>I never heard of any boy or girl who didn't know the Big Dipper. But
+there is one very pleasant thing about the Dipper which children never
+seem to know. With the aid of these seven magnificent stars you can find
+all the other interesting stars and constellations. So true is this that
+a book has been written called "The Stars through a Dipper."</p>
+
+<p>To illustrate, do you know the <i>Pointers</i>? I mean the two stars on the
+front side of the Dipper. They point almost directly toward the Pole
+star, or North star, the correct name of which is Polaris. Most children
+can see the Pole star at once because it is the only bright star in that
+part of the heavens.</p>
+
+<p>But if you can't be sure you see the right one, a funny thing happens.
+Your friend will try to show you by pointing, but even if you look
+straight along his arm you can't always be sure. And then, if he tries
+to tell you how far one star is from another, he will try to show you by
+holding his arms apart. But that fails also. And so, we all soon learn
+the easiest and surest way to point out stars and measure distances.</p>
+
+<p>The easiest way to tell any one how to find a star<span class='pagenum'><a name="Page_208" id="Page_208">[Pg 208]</a></span> is to get three
+stars in a straight line, or else at right angles.</p>
+
+<p>The surest way to tell any one how far one star is from another is by
+"degrees." You know what degrees are, because every circle is divided
+into 360 of them. And if you will think a moment, you will understand
+why we can see only half the sky at any one time, or 180 degrees,
+because the other half of the sky is on the other side of the earth.
+Therefore, if you draw a straight line from one horizon, clear up to the
+top of the sky and down to the opposite horizon, it is 180 degrees long.
+And, of course, it is only half that distance, or 90 degrees, from
+horizon to zenith. (Horizon is the point where earth and sky seem to
+meet, and zenith is the point straight over your head.)</p>
+
+<p>Now ninety degrees is a mighty big distance in the sky. The Pole star is
+nothing like ninety degrees from the Dipper. It is only twenty-five
+degrees, or about five times the distance between the Pointers. And now
+comes the only thing I will ask you to remember. Look well at the two
+Pointers, because the distance between them, five degrees, is the most
+convenient "foot rule" for the sky that you will ever find. Most of the
+stars you will want to talk about are from two to five times that
+distance from some other star that you and your friends are sure of.
+Perhaps this is a little hard to understand. If so, read it over several
+times, or get some one to explain it to you, for when you grasp it, it
+will unlock almost<span class='pagenum'><a name="Page_209" id="Page_209">[Pg 209]</a></span> as many pleasures as a key to the store you like the
+best.</p>
+
+<p>Now, let's try our new-found ruler. Let us see if it will help us find
+the eighth star in the Dipper. That's a famous test of sharp eyes. I
+don't want to spoil your pleasure by telling you too soon where it is.
+Perhaps you would rather see how sharp your eyes are before reading any
+further. But if you can't find the eighth star, I will tell you where to
+look.</p>
+
+<p>Look at the second star in the Dipper, counting from the end of the
+handle. That is a famous star called Mizar. Now look all around Mizar,
+and then, if you can't see a little one near it, try to measure off one
+degree. To do this, look at the Pointers and try to measure off about a
+fifth of the distance between them. Then look about one degree (or less)
+from Mizar, and I am sure you will see the little beauty&mdash;its name is
+Alcor, which means "the cavalier" or companion. The two are sometimes
+called "<i>the horse and rider</i>"; another name for Alcor is Saidak, which
+means "the test." I shall be very much disappointed if you cannot see
+Saidak, because it is not considered a hard test nowadays for sharp
+eyes.</p>
+
+<p>Aren't these interesting names? Mizar, Alcor, Saidak. They sound so
+Arabian, and remind one of the "Arabian Nights." At first, some of them
+will seem hard, but you will come to love these old names. I dare say
+many of these star names are 4,000 years old. Shepherds and sailors
+were<span class='pagenum'><a name="Page_210" id="Page_210">[Pg 210]</a></span> the first astronomers. The sailors had to steer by the stars, and
+the shepherds could lie on the ground and enjoy them without having to
+twist their necks. They saw and named Alcor, thousands of years before
+telescopes were invented, and long before there were any books to help
+them. They saw the demon star, too, which I have never seen. It needs
+patience to see those things; sharp eyes are nothing to be proud of,
+because they are given to us. But patience is something to be eager
+about, because it costs us a lot of trouble to get it.</p>
+
+<p>Let's try for it. We've had a test of sight. Now let's have a test of
+patience. It takes more patience than sharpness of sight to trace the
+outline of the Little Dipper. It has seven stars, too, and the Pole star
+is in the end of the handle. Do you see two rather bright stars about
+twenty-five degrees from the Pole? I hope so, for they are the only
+brightish stars anywhere near Polaris. Well, those two stars are in the
+outer rim of the Little Dipper. Now, I think you can trace it all; but
+to make sure you see the real thing, I will tell you the last secret.
+The handle of the Big Dipper is bent <i>back</i>; the handle of the Little
+Dipper is bent <i>in</i>.</p>
+
+<p>Now, if you have done all this faithfully, you have worked hard enough,
+and I will reward you with a story. Once upon a time there was a
+princess named Callisto, and the great god Jupiter fell in love with
+her. Naturally, Jupiter's wife, Juno, wasn't pleased, so she changed the
+princess into a bear. But before<span class='pagenum'><a name="Page_211" id="Page_211">[Pg 211]</a></span> this happened, Callisto became the
+mother of a little boy named Arcas, who grew up to be a mighty hunter.
+One day he saw a bear and he was going to kill it, not knowing that the
+bear was really his own mother. Luckily Jupiter interfered and saved
+their lives. He changed Arcas into a bear and put both bears into the
+sky. Callisto is the Big Bear, and Arcas is the Little Bear. But Juno
+was angry at that, and so she went to the wife of the Ocean and said,
+"Please, never let these bears come to your home." So the wife of the
+Ocean said, "I will never let them sink beneath the waves." And that is
+why the Big and the Little Dipper never set. They always whirl around
+the Pole star. And that is why you can always see them, though some
+nights you would have to sit up very late.</p>
+
+<p>Is that a true story? No. But, I can tell you a true one that is even
+more wonderful. Once upon a time, before the bear story was invented and
+before people had tin dippers, they used to think of the Little Dipper
+as a little dog. And so they gave a funny name to the Pole star. They
+called it Cynosura, which means "the dog's tail." We sometimes say of a
+great man, "he was the cynosure of all eyes," meaning that everybody
+looked at him. But the original cynosure was and is the Pole star,
+because all the stars in the sky seem to revolve around it. The two
+Dippers chase round it once every twenty-four hours, as you can convince
+yourself some night when you stay up late. So that's all for to-night.<span class='pagenum'><a name="Page_212" id="Page_212">[Pg 212]</a></span></p>
+
+<p>What! You want another true story? Well, just one more. Once upon a time
+the Big Dipper was a perfect cross. That was about 50,000 years ago.
+Fifty thousand years from now the Big Dipper will look like a steamer
+chair. How do I know that? Because, the two stars at opposite ends of
+the Dipper are going in a direction different from the other five stars.
+How do I know that? Why, I don't know it. I just believe it. There are
+lots of things I don't know, and I'm not afraid to say so. I hope you
+will learn how to say "I don't know." It's infinitely better than
+guessing; it saves trouble, and people like you better, because they see
+you are honest. I don't know how the stars in the Big Dipper are moving,
+but the men who look through telescopes and study mathematics say the
+end stars do move in a direction opposite to the others, and they say
+the Dipper <i>must</i> have looked like a cross, and will look like a dipper
+long, long after we are dead. And I believe them.<span class='pagenum'><a name="Page_213" id="Page_213">[Pg 213]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="CONSTELLATIONS_YOU_CAN_ALWAYS_SEE" id="CONSTELLATIONS_YOU_CAN_ALWAYS_SEE"></a>CONSTELLATIONS YOU CAN ALWAYS SEE</h2>
+
+
+<p>There are forty-eight well known constellations, but of these only about
+a dozen are easy to know. I think a dozen is quite enough for children
+to learn. And therefore, I shall tell you how to find only the showiest
+and most interesting.</p>
+
+<p>The best way to begin is to describe the ones that you can see almost
+every night in the year, because you may want to begin any month in the
+year, and you might be discouraged if I talked about things nobody could
+see in that month. There are five constellations you can nearly always
+see, and these are all near the Pole star.</p>
+
+<p>Doubtless you think you know two of them already&mdash;the Big and the Little
+Dipper. Ah, I forgot to tell you that these dippers are not the real
+thing. They are merely parts of bigger constellations and their real
+names are Great Bear and Little Bear. The oldest names are the right
+ones. Thousands of years ago, when the Greeks named these groups of
+stars, they thought they looked like two bears. I can't see the
+resemblance.</p>
+
+<p>But for that matter all the figures in the sky are disappointing. The
+people who named the constellations called them lions, and fishes, and
+horses, and<span class='pagenum'><a name="Page_214" id="Page_214">[Pg 214]</a></span> hunters, and they thought they could see a dolphin, a
+snake, a dragon, a crow, a crab, a bull, a ram, a swan, and other
+things. But nowadays we cannot see those creatures. We can see the stars
+plainly enough, and they do make groups, but they do not look like
+animals. I was greatly disappointed when I was told this; but I soon got
+over it, because new wonders are always coming on. I think the only
+honest thing to do is to tell you right at the start that you cannot see
+these creatures very well. You will spoil your pleasure unless you take
+these resemblances good-naturedly and with a light heart. And you will
+also spoil your pleasure if you scold the ancients for naming the
+constellations badly. Nobody in the world would change those old names
+now. There is too much pleasure in them. Besides, I doubt if we could do
+much better. I believe those old folks were better observers than we.
+And I believe they had a lighter fancy.</p>
+
+<p>Let us, too, be fanciful for once. I have asked my friend, Mrs. Thomas,
+to draw her notion of some of these famous creatures of the sky. You can
+draw your idea of them too, and it is pleasant to compare drawings with
+friends. There is only one way to see anything like a Great Bear. You
+have to imagine the Dipper upside down and make the handle of the Dipper
+serve for the Bear's tail. What a funny bear to drag a long tail on the
+ground! Miss Martin says he looks more like a chubby hobby-horse. You
+will have to make the bowl of the Dipper into hind legs and use all the
+other stars, somehow, to make a big, clumsy, four-legged animal. And
+what a monster he is! He measures twenty-five degrees from the tip of
+his nose to the root of his tail. Yes, all those miscellaneous faint
+stars you see near the Big Dipper belong to the Great Bear.</p>
+
+<div class="figcenter" style="width: 308px;">
+<img src="images/illus214_th.jpg" width="308" height="500" alt="Orion fighting the Bull. Above are Orion&#39;s two dogs" title="" />
+<span class="caption">Orion fighting the Bull. Above are Orion&#39;s two dogs</span>
+</div>
+
+<div class="figcenter" style="width: 308px;">
+<img src="images/illus215_th.jpg" width="308" height="500" alt="The Little Bear, the Queen in her chair, the Twins and
+the Archer" title="" />
+<span class="caption">The Little Bear, the Queen in her chair, the Twins and
+the Archer</span>
+</div><p><span class='pagenum'><a name="Page_215" id="Page_215">[Pg 215]</a></span></p>
+
+<p>How the Great Bear looked to the people who named it thousands of years
+ago, we probably shall never know. They left no books or drawings, so
+far as I know. But in every dictionary and book on astronomy you can
+find these bears and other animals drawn so carefully and beautifully
+that it seems as if they <i>must</i> be in the sky, and we must be too dull
+to see them. It is not so. Look at the pictures in this book and, you
+will see that the stars do not outline the animals. Many of them come at
+the wrong places. And so it is with all the costly books and charts and
+planispheres. It is all very interesting, but it isn't true. It's just
+fancy. And when you once understand that it isn't true, you will begin
+to enjoy the fancy. Many a smile you will have, and sometimes a good
+laugh. For instance, the English children call the Dipper "Charles's
+wain" or "the wagon." And the Romans called it "the plough." They
+thought of those seven stars as oxen drawing a plough.</p>
+
+<p>Well, that's enough about the two Bears. I want to tell you about the
+other three constellations you can nearly always see. These are the
+Chair, the Charioteer, and Perseus (pronounced <i>per'soos</i>).<span class='pagenum'><a name="Page_216" id="Page_216">[Pg 216]</a></span></p>
+
+<p>The Chair is the easiest to find, because it is like a very bad W, and
+it is always directly opposite the big Dipper, with the Pole star half
+way between the two constellations. There are five stars in the W, and
+to make the W into a Chair you must add a fainter star which helps to
+make the square bottom of the chair. But what a crazy piece of
+furniture! I have seen several ways of drawing it, but none of them
+makes a comfortable chair. I should either fall over backward, or else
+the back of the chair would prod me in the small of my back. The correct
+name of this constellation is Cassiopeia's Chair.</p>
+
+<p>I think this is enough to see and enjoy in one night. To-morrow night
+let us look for the Charioteer.</p>
+
+<p>I love the Charioteer for several reasons. One is that it makes a
+beautiful pentagon, or five-sided figure, with its five brightest stars.
+Another is that it contains the second-brightest star in the northern
+part of the heavens, Capella. The only star in the north that is
+brighter is Vega, but Vega is bluish white or creamy.</p>
+
+<p>If you haven't already found the five-sided figure, I will tell you how
+to find Capella. Suppose you had a gun that would shoot anything as far
+as you wish. Shoot a white string right through the Pointers and hit the
+Pole star. Then place your gun at the Pole star and turn it till it is
+at right angles to that string you shot. Aim away from the big Dipper,
+shoot a bullet forty-five degrees and it will hit Capella.</p>
+
+<p>If that plan doesn't work, try this. Start with the<span class='pagenum'><a name="Page_217" id="Page_217">[Pg 217]</a></span> star that is at the
+bottom of the Dipper and nearest the handle. Draw a line half-way
+between the two Pointers and keep on till you come to the first bright
+star. This is Capella, and the distance is about fifty degrees.</p>
+
+<p>Capella means "a kid," or "little goat," and that reminds me of the
+third reason why I enjoy so much the constellation of which Capella is
+the brightest star. In the old times they sometimes called this
+five-sided figure "the goat-carrier." And the shepherds thought they
+could see a man carrying a little goat in his left hand. I am sure you
+can see the kid they meant. It is a triangle of faint stars which you
+see near Capella. That's enough for to-night.</p>
+
+<p>To-morrow night let us look for Perseus. I dare say you know that old
+tale about Perseus rescuing the princess who was chained upon a rock.
+(He cut off the snaky head of Medusa and showed it to the dragon that
+was going to devour the princess, and it turned the monster to stone.
+Remember?) Well, there are constellations named after all the people in
+that story, but although they contain many showy stars, I could never
+make them look like a hero, a princess, a king, and a queen. I do not
+even try to trace out all of Perseus. For I am satisfied to enjoy a very
+beautiful part of it which is called the "Arc of Perseus."</p>
+
+<p>An arc, you know, is a portion of a circle. And the way to find this arc
+is to draw a curve from Capella to Cassiopeia. On nights that are not
+very<span class='pagenum'><a name="Page_218" id="Page_218">[Pg 218]</a></span> clear I can see about seven stars in this Arc of Perseus. And the
+reason I love it so much is that it is the most beautiful thing, when
+seen through an opera-glass, that I know. You could never imagine that a
+mere opera-glass would make such a difference. The moment I put it to my
+eyes about a dozen more stars suddenly leap into my sight in and near
+the Arc of Perseus. That's enough. No more stories to-night.<span class='pagenum'><a name="Page_219" id="Page_219">[Pg 219]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="WINTER_CONSTELLATIONS" id="WINTER_CONSTELLATIONS"></a>WINTER CONSTELLATIONS</h2>
+
+
+<p>By winter constellations I mean those you can see in winter at the
+pleasantest time&mdash;the early evening. And I want you to begin with the
+Northern Cross. I hope you can see this before Christmas, for, after
+that, it may be hidden by trees or buildings in the west and you may not
+see it again for a long while. This is because the stars seem to rise in
+the east and set in the west. To prove this, choose some brilliant star
+you can see at five or six o'clock; get it in line with some bush or
+other object over which you can just see it. Put a stake where you
+stand, and then go to the same spot about eight o'clock or just before
+you go to bed. You can tell at once how much the star seems to have
+moved westward.</p>
+
+<p>Another thing, every star rises four minutes later every night, and
+therefore the sky looks a little different at the same hour every
+evening. The stars in the north set for a short time only, but when
+those toward the south set they are gone a long time. For instance, the
+brightest star of all is Sirius, the Dog Star, which really belongs to
+the southern hemisphere. There are only about three months in the year
+when children who go to bed by seven<span class='pagenum'><a name="Page_220" id="Page_220">[Pg 220]</a></span> o'clock can see it&mdash;January,
+February, and March.</p>
+
+<p>So now you understand why I am so eager that you should not miss the
+pleasure of seeing the famous Northern Cross. But although it is a big
+cross, and easy to find, after you know it, I have never yet known a boy
+who could show it to another boy simply by pointing at it. The surest
+and best way to find it is learn three bright stars first&mdash;Altair, Vega,
+and Deneb.</p>
+
+<p>Altair is the brightest star in the Milky Way. It is just at the edge of
+the Milky Way, and you are to look for three stars in a straight line,
+with the middle one brightest. Those three stars make the constellation
+called "the Eagle." The body of the eagle is Altair, and the other two
+stars are the wings. I should say that Altair is about five degrees from
+each of his companions. It is worth half an hour's patient search to
+find the Eagle. Now these three stars in the Eagle point straight toward
+the brightest star in the northern part of the sky&mdash;Vega.</p>
+
+<p>To make sure of it, notice four fainter stars near it which make a
+parallelogram&mdash;a sort of diamond. These stars are all part of a
+constellation called "the Lyre." If you try to trace out the old musical
+instrument, you will be disappointed; but here is a game worth while.
+Can you see a small triangle made by three stars, of which Vega is one?
+Well, one of those stars is double, and with an opera-glass you can see
+which it is. On very clear nights some<span class='pagenum'><a name="Page_221" id="Page_221">[Pg 221]</a></span> people with very sharp eyes can
+see them lying close together, but I never could.</p>
+
+<p>At last we are ready to find the celebrated Northern Cross. First draw a
+line from Altair to Vega. Then draw a line at right angles to this,
+until you come to another bright star&mdash;Deneb&mdash;which is about as far from
+Vega as Vega is from Altair. Now this beautiful star, Deneb, is the top
+of the Northern Cross. I can't tell you whether the Cross will be right
+or wrong side up when you see it, or on its side. For every
+constellation is likely to change its position during the night, as you
+know from watching the Dipper. But you can tell the Cross by these
+things. There are six stars in it. It is like a kite made of two sticks.
+There are three stars in the crosspiece and four in the long piece.
+Deneb, the brightest star in the cross, is at the top of the long stick.</p>
+
+<p>But you mustn't expect to see a perfect cross. There is one star that is
+a little out of place, and sometimes my fingers fairly "itch to put it
+where it belongs." It is the one that ought to be where the long stick
+of your kite is tacked to the crosspiece. And one of the stars is
+provokingly faint, but you can see it. Counting straight down the long
+piece, it is the third one from Deneb that is faint. It is where it
+ought to be, but I should like to make it brighter. Have you the Cross
+now? If not, have patience. You can't be a "true sport" unless you are
+patient. You can't be a great ball-player, or hunter, or any thing else,
+without resisting, every day,<span class='pagenum'><a name="Page_222" id="Page_222">[Pg 222]</a></span> that sudden impulse to "quit the game"
+when you lose. Be a "good loser," smile and try again. That is better
+than to give up, or to win by cheating or sharp practice.</p>
+
+<p>This is the last thing I want you to see in the northern part of the
+sky; and if you have done a good job, let us celebrate by having a
+story.</p>
+
+<p>Once upon a time a cross didn't mean so much to the world as it does
+now. That was before Christ was born. In those old times people did not
+think of the Northern Cross as a cross. They thought of it as a Swan,
+and you can see the Swan if you turn the Cross upside down. Deneb will
+then be in the tail of the Swan, and the two stars which used to be at
+the tips of the crosspiece now become the wings. Is that a true story?
+Yes. If we lived in Arabia the children there could tell us what Deneb
+means. It means "the tail."</p>
+
+<p>Another story? Well, do you see the star in the beak of the Swan, or
+foot of the Cross? What color is it? White? Well, they say this white
+star is really made up of two stars&mdash;one yellow and the other blue. That
+is one reason I want to buy a telescope when I can afford it, for even
+the smallest telescope will show that. And Mr. Serviss says that even a
+strong field-glass will help any one see this wonder.</p>
+
+<p>I can't tell you about all the winter constellations in one chapter. We
+have made friends of the northern ones. Now let's see the famous
+southern ones. And let's start a new chapter.<span class='pagenum'><a name="Page_223" id="Page_223">[Pg 223]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="ORION_HIS_DOGS_AND_THE_BULL" id="ORION_HIS_DOGS_AND_THE_BULL"></a>ORION, HIS DOGS, AND THE BULL</h2>
+
+
+<p>The most gorgeous constellation in the whole sky is Orion. I really pity
+any one who does not know it, because it has more bright stars in it
+than any other group. Besides, it doesn't take much imagination to see
+this mighty hunter fighting the great Bull. I dare say half the people
+in the United States know Orion and can tell him as quick as they see
+him by the famous "belt of Orion."</p>
+
+<p>This belt is made of three stars, each of which is just one degree from
+the next. That is why the English people call these three stars "the ell
+and yard." Another name for them is "the three kings." You can see the
+"sword of Orion" hanging down from his belt.</p>
+
+<p>As soon as you see these things you will see the four bright stars that
+outline the figure of the great hunter, but only two of them are of the
+first magnitude. The red one has a hard name&mdash;Betelgeuse (pronounced
+<i>bet-el-guz&acute;</i>). That is a Frenchified word from the Arabic, meaning
+"armpit," because this star marks the right shoulder of Orion. The other
+first-magnitude star is the big white one in the left foot. Its name is
+Rigel (pronounced <i>re&acute;-jel</i>) from an Arabian word meaning "the foot."<span class='pagenum'><a name="Page_224" id="Page_224">[Pg 224]</a></span></p>
+
+<p>You can see the giant now, I am sure. Over his left arm hangs a lion's
+skin which he holds out to shield him from the bull's horns. See the
+shield&mdash;about four rather faint stars in a pretty good curve? Now look
+for his club which he holds up with his right hand so as to smite the
+bull. See the arm and the club&mdash;about seven stars in a rather poor
+curve&mdash;beyond the red star Betelgeuse? Now you have him, and isn't he a
+wonder!</p>
+
+<p>It is even easier to see the Bull which is trying to gore Orion. Look
+where Orion is threatening to strike, and you will see a V. How many
+stars in that V? Five. And which is the brightest? That red one at the
+top of the left branch of the V? Yes. That V is the face of the Bull and
+that red star is the baleful eye of the angry Bull which is lowering his
+head and trying to toss Orion. The name of that red eye is Aldebaran
+(pronounced <i>al-deb&acute;-ar-an</i>).</p>
+
+<p>I wish Aldebaran meant "red eye," but it doesn't. It is an old Arabian
+word meaning the "hindmost," or the "follower," because every evening it
+comes into view about an hour after you can see the famous group of
+stars called the Pleiades, which are in the shoulder of the Bull.</p>
+
+<p>I do not care to trace the outline of this enormous bull, but his horns
+are a great deal longer than you think at first. If you will extend the
+two arms of that V a long way you will see two stars which may be called
+the tips of his horns. One of these stars really belongs in another
+constellation&mdash;our old<span class='pagenum'><a name="Page_225" id="Page_225">[Pg 225]</a></span> friend the Charioteer, the one including
+Capella. Wow! what a pair of horns!</p>
+
+<p>But now we come to the daintiest of all constellations&mdash;the Seven
+Sisters, or Pleiades (pronounced <i>plee&acute;-a-deez</i>).</p>
+
+<p>I can see only six of them, and there is a famous old tale about the
+"lost Pleiad." But I needn't describe them. Every child finds them by
+instinct. Some compare them to a swarm of bees; some to a rosette of
+diamonds; some to dewdrops. But I would not compare them to a dipper as
+some do, because the real Little Dipper is very different. The light
+that seems to drip from the Pleiades is quivering, misty, romantic,
+magical. No wonder many children love the Pleiades best of all the
+constellations. No wonder the poets have praised them for thousands of
+years. The oldest piece of poetry about them that I know of was written
+about 1,500 years before Christ. You can find it in the book of Job. But
+the most poetic description of the Pleiades that I have ever read is in
+Tennyson's poem "Locksley Hall," in which he says they "glitter like a
+swarm of fireflies tangled in a silver braid."</p>
+
+<p>There are a great many old tales about the lost Pleiad. One is that she
+veiled her face because the ancient city of Troy was burned. Another
+story says she ceased to be a goddess when she married a man and became
+mortal. Some people think she was struck by lightning. Others believe
+the big star,<span class='pagenum'><a name="Page_226" id="Page_226">[Pg 226]</a></span> Canopus, came by and ran away with her. Still others
+declare she was a new star that appeared suddenly once upon a time, and
+after a while faded away.</p>
+
+<p>For myself, I do not believe any of these stories. One reason why I
+don't is that a seventh star is really there, and many people can really
+see it. Indeed, there are some people so sharp-eyed that on clear nights
+they can see anywhere from eight to eleven. And, what is more, they can
+draw a map or chart showing just where each star seems to them to be.</p>
+
+<p>But the most wonderful stories about the Pleiades are the true stories.
+One is that there are really more than 3,000 stars among the Pleiades.
+Some of them can be seen only with the biggest telescopes. Others are
+revealed only by the spectroscope. And some can be found only by means
+of photography.</p>
+
+<p>But the most amazing thing about the Pleiades is the distances between
+them. They look so close together that you would probably say "the moon
+seems bigger than all of them put together." Sometimes the moon comes
+near the Pleiades, and you expect that the moon will blot them all out.
+But the astronomers say the full moon sails through the Pleiades and
+covers only one of them at a time, as a rule. They even say it is
+possible for the moon to pass through the Pleiades without touching one
+of them! I should like to see that. If anything like it is going to
+occur, the magazine I spoke of in the<span class='pagenum'><a name="Page_227" id="Page_227">[Pg 227]</a></span> first chapter will tell me about
+it. And you'd better believe I will stay up to see that, if it takes all
+night!</p>
+
+<p>There are two more constellations in the southern part of the sky that
+ought to be interesting, because they are the two hunting dogs that help
+Orion fight the Bull. But I can't trace these animals, and I don't
+believe it is worth while. The brightest stars in them everybody can see
+and admire&mdash;Sirius, the Bigger Dog, and Procyon, the Smaller Dog.</p>
+
+<p>Every one ought to know Sirius, because he is the brightest star of all.
+(Of course, he is not so bright as Venus and Jupiter, but they are
+planets.) To find him, draw a line from the eye of the Bull through the
+belt of Orion and extend it toward the southeast about twenty degrees.
+They call him the Dog star because he follows the heels of Orion. And
+people still call the hottest days of summer "dog days" because 400
+years before Christ the Romans noticed that the Dog star rose just
+before the sun at that time. The Romans thought he chased the sun across
+the sky all day and therefore was responsible for the great heat. But
+that was a foolish explanation. And so is the old notion that dogs are
+likely to go mad during the dog days "because the dog star is in the
+ascendant." So is the idea that Sirius is an unlucky star.</p>
+
+<p>There are no lucky or unlucky stars. These are all superstitions, and we
+ought to be ashamed to believe any superstition. Yet for thousands of
+years<span class='pagenum'><a name="Page_228" id="Page_228">[Pg 228]</a></span> before we had public schools and learned to know better, people
+believed that every one was born under a lucky star or an unlucky one,
+and they believe that farmers ought to plant or not plant, according to
+the size of the moon. Now we know that is all bosh. Those old
+superstitions have done more harm than good. One of the most harmful was
+the belief in witches. Let us resolve never to be afraid of these old
+tales, but laugh at them.</p>
+
+<p>Why should anybody be afraid of anything so lovely as Sirius? I used to
+think Sirius twinkled more than any other star. But that was bad
+reasoning on my part. I might have noticed that every star twinkles more
+near the horizon than toward the zenith. I might have noticed that stars
+twinkle more on clear, frosty nights than when there is a little uniform
+haze. And putting those two facts together I might have reasoned that
+the stars never really twinkle at all; they only seem to. I might have
+concluded that the twinkling is all due to the atmosphere&mdash;that blanket
+of air which wraps the earth around. The nearer the earth, the thicker
+the air, and the more it interferes with the light that comes to us from
+the stars.</p>
+
+<p>They say that Sirius never looks exactly alike on two successive nights.
+"It has a hundred moods," says Mr. Serviss, "according to the state of
+the atmosphere. By turns it flames, it sparkles, it glows, it blazes, it
+flares, it flashes, it contracts to a point, and sometimes when the air
+is still, it burns with a<span class='pagenum'><a name="Page_229" id="Page_229">[Pg 229]</a></span> steady white light." (Quotation somewhat
+altered and condensed.)</p>
+
+<p>It is a pity that so fine a star as Procyon should be called the
+"Smaller Dog," because it suffers unjustly by comparison with Sirius. If
+it were in some other part of the sky we might appreciate it more,
+because it is brighter than most of the fifteen first-magnitude stars we
+can see. My brother William has grown to love it, but perhaps that is
+because he always "sympathizes with the under dog." He was the youngest
+brother and knows. And curiously enough he was nicknamed "the dog"&mdash;just
+why, I don't know.</p>
+
+<p>To find Procyon, drawn a line from Sirius northeast about twenty
+degrees. And to make sure, draw one east from Betelgeuse about the same
+distance. These three stars make a triangle of which the sides are
+almost equal.</p>
+
+<p>The name Procyon means "before the dog" referring to the fact that you
+can see him fifteen or twenty minutes earlier every night than you can
+see Sirius.</p>
+
+<p>The only kind word about Procyon I have heard in recent years was in
+connection with that miserable business of Dr. Cook and the North Pole.
+A Captain Somebody-or-other was making observations for Dr. Cook, and he
+wanted to know what time it was. He had no watch and didn't want to
+disturb any one. So he looked out of the window and saw by the star
+Procyon that it was eleven o'clock.<span class='pagenum'><a name="Page_230" id="Page_230">[Pg 230]</a></span></p>
+
+<p>That sounds mysterious, but it is easy if you have a planisphere like
+ours. Last winter when we were all enjoying Orion, the Bull, and the two
+Dogs, I used to whirl the planisphere around to see where they would be
+at six o'clock at night, at eight, at ten, at midnight, and even at six
+o'clock in the morning. And so, if I waked up in the night I could tell
+what time it was without even turning my head. Sometimes I looked out of
+my window, saw Orion nearly overhead and knew it must be midnight. And
+sometimes I woke up just before daybreak and saw the great Bull backing
+down out of sight in the west, the mighty Hunter still brandishing his
+club, and his faithful Dogs following at his heels.<span class='pagenum'><a name="Page_231" id="Page_231">[Pg 231]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="SEVEN_FAMOUS_CONSTELLATIONS" id="SEVEN_FAMOUS_CONSTELLATIONS"></a>SEVEN FAMOUS CONSTELLATIONS</h2>
+
+
+<p>There are only seven more constellations that seem to me interesting
+enough for every one to know and love all his life. These are:</p>
+
+
+<div class='center'>
+<table border="0" cellpadding="4" cellspacing="0" summary="">
+<tr><td align='left'>The Lion (Spring)</td><td align='left'>The Herdsman (Summer)</td></tr>
+<tr><td align='left'>The Twins (Spring)</td><td align='left'>The Northern Crown (Summer)</td></tr>
+<tr><td align='left'>The Virgin (Summer)</td><td align='left'>The Scorpion (Summer)</td></tr>
+<tr><td align='center' colspan='2'>Southern Fish (Autumn)</td></tr>
+</table></div>
+
+<p>I have named the seasons when, according to some people, these
+constellations are most enjoyable. But these are not the only times when
+you can see them. (If you had that seventy-five-cent planisphere, now,
+you could always tell which constellations are visible and just where to
+find them.) No matter what time of year you read this chapter, it is
+worth while to go out and look for these marvels. You can't possibly
+miss them all.</p>
+
+<p>Have you ever seen a Sickle in the sky? It's a beauty, and whenever I
+have seen it it has been turned very conveniently for me, because I am
+left-handed. It is so easy to find that I am almost ashamed to tell. But
+if you need help, draw a line through the Pointers backward, away from
+the Pole star, about forty degrees, and it will come a little<span class='pagenum'><a name="Page_232" id="Page_232">[Pg 232]</a></span> west of
+the Sickle. The Sickle is only part of the Lion&mdash;the head and the
+forequarters. Only fanciful map-makers can trace the rest of the Lion.
+The bright star at the end of the handle is Regulus, which means "king,"
+from the stupid old notion that this star ruled the lives of men. To
+this day people speak of the "Royal Star," meaning Regulus. And at the
+end of this chapter I will tell you about three other stars which the
+Persians called "royal stars."</p>
+
+<p>Another constellation which children particularly love is the
+Twins&mdash;Castor and Pollux. But the sailors got there first! For thousands
+of years the twins have been supposed to bring good luck to sailors. I
+don't believe a word of it. But I do know that sailors gloat over Castor
+and Pollux, and like them better than any other stars. The whole
+constellation includes all the stars east of the Bull and between the
+Charioteer and Procyon. But another way to outline the twins is to look
+northeast of Orion where you will see two rows of stars that run nearly
+parallel. To me the brothers seem to be standing, but all the old
+picture-makers show them sitting with their arms around each other, the
+two brightest stars being their eyes. The eyes are about five degrees
+apart&mdash;the same as the Pointers.</p>
+
+<p>Pollux is now brighter than Castor, but for thousands of years it was
+just the other way. It is only within three hundred years that this
+change has taken place. Whether Castor has faded or Pollux brightened,
+or both, I do not know. Anyhow,<span class='pagenum'><a name="Page_233" id="Page_233">[Pg 233]</a></span> Castor is not quite bright enough to be
+a first magnitude star. Three hundred years is a short time in the
+history of man, and only a speck in the history of the stars. Three
+hundred years ago they killed people in Europe just because of the
+church they went to. That was why the Pilgrim Fathers sailed from
+England in 1620, and made the first permanent settlement in America,
+except, of course, Jamestown, Va., in 1607.</p>
+
+<p>There are plenty of stories about old Castor and Pollux, and, like all
+the other myths, they conflict, more or less. But all agree that these
+two brothers went with Jason in the ship Argo, shared his adventures and
+helped him get the golden fleece. And all agree that Castor and Pollux
+were "born fighters." And that is why the Roman soldiers looked up to
+these stars and prayed to them to help them win their battles.</p>
+
+<p>Now for the four summer constellations every one ought to know. The
+first thing to look for is two famous red or reddish stars&mdash;Arcturus and
+Antares.</p>
+
+<p>The way you find Arcturus is amusing. Look for the Big Dipper and find
+the star at the bottom of the dipper nearest the handle. Got it? Now
+draw a curve that will connect it with all the stars in the handle, and
+when you come to the end of the handle keep on till you come to the
+first very bright star&mdash;about twenty-five degrees. That is the monstrous
+star Arcturus, probably the biggest and swiftest star we can ever see
+with the naked eye in<span class='pagenum'><a name="Page_234" id="Page_234">[Pg 234]</a></span> the northern hemisphere. He is several times as
+big as our sun, and his diameter is supposed to be several million
+miles. He is called a "runaway sun," because he is rushing through space
+at the rate of between two hundred and three hundred miles a second.
+That means between seventeen and thirty-four million miles a day!</p>
+
+<p>He is coming toward us, too! At such a rate you might think that
+Arcturus would have smashed the earth to pieces long ago. But he is
+still very far away, and there is no danger. Some people say that if Job
+were to come to life, the sky would seem just the same to him as it did
+3,400 years ago. The only difference he might notice would be in
+Arcturus. That would seem to him out of place by a distance about three
+times the apparent diameter of the moon.</p>
+
+<p>Some people believe this because Job said, "Canst thou guide Arcturus
+with his sons?" and therefore they imagine that he meant this red star.
+But I believe he meant the Big Dipper. For in King James's time, when
+the Bible was translated into English, the word "Arcturus" meant the Big
+Dipper or rather the Great Bear. And for centuries before it meant the
+Great Bear. One proof of it is that "Arcturus" comes from an old Greek
+word meaning "bear"&mdash;the same word from which we get arctic. It is only
+within a few hundred years that astronomers have agreed to call the
+Great Bear "Ursa Major," and this red star Arcturus. So I<span class='pagenum'><a name="Page_235" id="Page_235">[Pg 235]</a></span> think all the
+books which say Job mentioned this red star are mistaken. I believe
+Webster's Dictionary is correct in this matter, and I believe the
+Revised Version translates Job's Hebrew phrase more correctly when it
+says, "Canst thou guide the Bear with her train?"</p>
+
+<p>Anyhow, Arcturus is a splendid star&mdash;the brightest in the constellation
+called the "Herdsman" or Bo&ouml;tes. It is not worth while to trace the
+Herdsman, but here is an interesting question. Is Arcturus really red?
+The books mostly say he is yellow. They say he looks red when he is low
+in the sky, and yellow when he is high. How does he look to you? More
+yellow than red?</p>
+
+<p>Well, there's no doubt about Antares being red. To find him, draw a long
+line from Regulus through Arcturus to Antares, Arcturus being more than
+half way between the other two. But if Regulus and the Sickle are not
+visible, draw a line from Altair, at right angles to the Eagle, until
+you come to a bright star about sixty degrees away. You can't miss
+Antares, for he is the only red star in that part of the sky.</p>
+
+<p>Antares belongs to a showy constellation called the Scorpion. I cannot
+trace all the outline of a spider-like creature, but his poisonous tail
+or "stinger" is made by a curved line of stars south and east of
+Antares. And you can make a pretty fan by joining Antares to several
+stars in a curve which are west of Antares and a little north. There<span class='pagenum'><a name="Page_236" id="Page_236">[Pg 236]</a></span> is
+an old tale that this Scorpion is the one that stung Orion to death when
+he began to "show off" and boast that there was no animal in the world
+that could kill him.</p>
+
+<p>Another very bright star in the southern part of the sky is Spica. To
+find it, start with the handle of the Dipper, and making the same
+backward curve which helped you to find Arcturus, keep on till you come
+to the white star Spica&mdash;say thirty degrees beyond Arcturus. This is the
+brightest star in the constellation called "the Virgin." It is not worth
+while trying to trace her among nearly forty faint stars in this
+neighbourhood. But she is supposed to be a winged goddess who holds up
+in her right hand an <i>ear of wheat</i>, and that is what Spica means.</p>
+
+<p>Now for an autumn constellation&mdash;the Southern Fish. I don't care if you
+fail to outline a fish, but I do want you to see the bright star that is
+supposed to be in the fish's mouth. And I don't want you to balk at its
+hard name&mdash;Fomalhaut (pronounced <i>fo&acute;-mal-o</i>). It is worth a lot of
+trouble to know it as a friend. To find it, you have to draw an
+exceedingly long line two-thirds of the way across the whole sky. Start
+with the Pointers. Draw a line through them and the Pole star and keep
+clear on until you come to a solitary bright star rather low down in the
+south. That is Fomalhaut. It looks lonely and is lonely, even when you
+look at it through a telescope.</p>
+
+<p>And now for the last story. Once upon a time<span class='pagenum'><a name="Page_237" id="Page_237">[Pg 237]</a></span> the Persians thought there
+must be four stars that rule the lives of men. So they picked out one in
+the north and one in the south and one in the east and one in the west,
+just as if they were looking for four bright stars to mark the points of
+the compass. If you want to find them yourself without my help don't
+read the next sentence, but shut this book and go out and see. Then
+write down on a piece of paper the stars you have selected and compare
+them with the list I am about to give. Here are the four royal stars of
+the Persians: Fomalhaut for the north, Regulus for the south, Aldebaran
+for the east, and Antares for the west.</p>
+
+<p>Why doesn't this list agree with yours? Because Persia is so far south
+of where we live. Ah, there are very few things that are absolutely
+true. Let's remember that and not be too sure: for everything depends
+upon the point of view! I hope you will see Fomalhaut before Christmas,
+before he disappears in the west. He is with us only five months and is
+always low&mdash;near the horizon. But the other seven months in the year he
+gladdens the children of South America and the rest of the southern
+hemisphere, for they see him sweeping high and lonely far up into their
+sky and down again.</p>
+
+<p>But the loveliest of all the constellations described in this chapter is
+the Northern Crown. It is not a perfect crown&mdash;only about half a
+circle&mdash;but enough to suggest a complete ring. Look for it east of
+Arcturus. I can see seven or eight stars in<span class='pagenum'><a name="Page_238" id="Page_238">[Pg 238]</a></span> the half-circle, one of
+which is brighter than all the others. That one is called "the Pearl."
+The whole constellation is only fifteen degrees long, but "fine things
+come in small packages"; and children grow to love the Northern Crown
+almost as much as they love the Pleiades.<span class='pagenum'><a name="Page_239" id="Page_239">[Pg 239]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_TWENTY_BRIGHTEST_STARS" id="THE_TWENTY_BRIGHTEST_STARS"></a>THE TWENTY BRIGHTEST STARS</h2>
+
+
+<p>If you have seen everything I have described so far, you have reason to
+be happy. For now you know sixteen of the most famous constellations and
+fifteen of the twenty brightest stars. There are only twenty stars of
+the first magnitude. "Magnitude" ought to mean size, but it doesn't. It
+means brightness&mdash;or rather the apparent brightness&mdash;of the stars when
+seen by us. The word magnitude was used in the old days before
+telescopes, when people thought the brighter a star is the bigger it
+must be. Now we know that the nearer a star is to us the brighter it is,
+and the farther away the fainter. Some of the bright stars are
+comparatively near us, some are very far. Deneb and Canopus are so far
+away that it takes over three hundred years for their light to reach us.
+What whoppers they must be&mdash;many times as big as our sun.</p>
+
+<p>Here is a full list of the twenty stars of the first magnitude arranged
+in the order of their brightness. You will find this table very useful.<span class='pagenum'><a name="Page_240" id="Page_240">[Pg 240]</a></span></p>
+
+
+
+<div class='center'>
+<table border="0" cellpadding="4" cellspacing="0" summary="">
+<tr><td align='center'>Stars</td><td align='center'>Pronounced</td><td align='center'>Constellation</td><td align='center'>Interesting facts</td></tr>
+<tr><td align='left'>Sirius</td><td align='left'><i>sir&acute;i-us</i></td><td align='left'>Big Dog</td><td align='left'>Brightest star. Nearest star visible in Northern hemisphere</td></tr>
+<tr><td align='left'>Canopus*</td><td align='left'><i>ca-no&acute;pus</i></td><td align='left'>Ship Argo</td><td align='left'>Perhaps the largest body in universe</td></tr>
+<tr><td align='left'>Alpha Centauri*</td><td align='left'><i>al&acute;fa sen-taw&acute;re</i></td><td align='left'>Centaur</td><td align='left'>Nearest star. Light four years away</td></tr>
+<tr><td align='left'>Vega</td><td align='left'><i>ve&acute;ga</i></td><td align='left'>Lyre</td><td align='left'>Brightest star in the Northern sky. Bluish</td></tr>
+<tr><td align='left'>Capella</td><td align='left'><i>ca-pell&acute;a</i></td><td align='left'>Charioteer</td><td align='left'>Rivals Vega, but opposite the pole. Yellowish</td></tr>
+<tr><td align='left'>Arcturus</td><td align='left'><i>ark-tu&acute;rus</i></td><td align='left'>Herdsman</td><td align='left'>Swiftest of the bright stars. 200 miles a second</td></tr>
+<tr><td align='left'>Rigel</td><td align='left'><i>re&acute;jel</i></td><td align='left'>Orion</td><td align='left'>Brightest star in Orion. White star in left foot</td></tr>
+<tr><td align='left'>Procyon</td><td align='left'><i>pro&acute;si-on</i></td><td align='left'>Little Dog</td><td align='left'>Before the dog. Rises a little before Sirius</td></tr>
+<tr><td align='left'>Achernar*</td><td align='left'><i>a-ker&acute;nar</i></td><td align='left'>River Po</td><td align='left'>Means the end of the river</td></tr>
+<tr><td align='left'>Beta Centauri*</td><td align='left'><i>ba&acute;ta sen-taw&acute;re</i></td><td align='left'>Centaur</td><td align='left'>This and its mate point to the Southern Cross</td></tr>
+<tr><td align='left'>Altair</td><td align='left'><i>al-tare&acute;</i></td><td align='left'>Eagle</td><td align='left'>Helps you find Vega and Northern Cross</td></tr>
+<tr><td align='left'>Betelgeuse</td><td align='left'><i>bet-el-guz&acute;</i></td><td align='left'>Orion</td><td align='left'>Means "armpit." The red star in the right shoulder</td></tr>
+<tr><td align='left'>Alpha Crucis*</td><td align='left'><i>al&acute;fa cru&acute;sis</i></td><td align='left'>Southern Cross</td><td align='left'>At the base of the most famous Southern constellation</td></tr>
+<tr><td align='left'>Aldebaran</td><td align='left'><i>al-deb&acute;a-ran</i></td><td align='left'>Bull</td><td align='left'>The red eye in the V</td></tr>
+<tr><td align='left'>Pollux</td><td align='left'><i>pol&acute;lux</i></td><td align='left'>Twins</td><td align='left'>Brighter than Castor</td></tr>
+<tr><td align='left'>Spica</td><td align='left'><i>spi&acute;ca</i></td><td align='left'>Virgin</td><td align='left'>Means ear of wheat</td></tr>
+<tr><td align='left'>Antares</td><td align='left'><i>an-ta&acute;rez</i></td><td align='left'>Scorpion</td><td align='left'>Red star. Name means "looks like Mars"</td></tr>
+<tr><td align='left'>Fomalhaut</td><td align='left'><i>fo&acute;mal-o</i></td><td align='left'>Southern Fish</td><td align='left'>The lonely star in the Southern sky</td></tr>
+<tr><td align='left'>Deneb</td><td align='left'><i>den&acute;eb</i></td><td align='left'>Swan</td><td align='left'>Top of Northern Cross, or tail of Swan</td></tr>
+<tr><td align='left'>Regulus</td><td align='left'><i>reg&acute;u-lus</i></td><td align='left'>Lion</td><td align='left'>The end of the handle of the Sickle</td></tr>
+</table></div>
+
+<p>The five stars marked * belong to the Southern hemisphere, and we can
+never see them unless we travel far south. Last winter I went to Florida
+and saw Canopus, but to see the Southern Cross you should cross the
+Tropic of Cancer.<span class='pagenum'><a name="Page_241" id="Page_241">[Pg 241]</a></span></p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="HOW_TO_LEARN_MORE" id="HOW_TO_LEARN_MORE"></a>HOW TO LEARN MORE</h2>
+
+
+<p>All I can hope to do in this book is to get you enthusiastic about
+astronomy. I don't mean "gushy." Look in the dictionary and you will
+find that the enthusiast is not the faddist. He is the one who sticks to
+a subject for a lifetime.</p>
+
+<p>Nor do I care a rap whether you become an astronomer&mdash;or even buy a
+telescope. There will be always astronomers coming on, but there are too
+few people who know and love even a few of the stars. I want you to make
+popular astronomy a life-long hobby. Perhaps you may have to drop it for
+ten or fifteen years. Never mind, you will take up the study again. I
+can't expect you to read a book on stars if you are fighting to make a
+living or support a family, unless it really rests you to read about the
+stars. It does rest me. When things go wrong at the office or at home, I
+can generally find rest and comfort from music. And if the sky is clear,
+I can look at the stars, and my cares suddenly seem small and drop away.</p>
+
+<p>Let me tell you why and how you can get the very best the stars have to
+teach you, without mathematics or telescope. Follow this programme and
+you need never be afraid of hard work, or of exhausting<span class='pagenum'><a name="Page_242" id="Page_242">[Pg 242]</a></span> the pleasures
+of the subject. Go to your public library and get one of the books I
+recommend in this chapter, and read whatever interests you. I don't care
+whether you take up planets before comets or comets before planets, but
+whatever you do do it well. Soak the interesting facts right in. Nail
+them down. See everything the book talks about. Make notes of things to
+watch for. Get a little blank book and write down the date you first saw
+each thing of interest. Write down the names of the constellations you
+love most. Before you lay down any star book you are reading, jot down
+the most wonderful and inspiring thing you have read&mdash;even if you have
+only time to write a single word that may recall it all to you. Treasure
+that little note book as long as you live. Every year it will get more
+precious to you.</p>
+
+<p>Now for the books:</p>
+
+<p>1. <i>Martin.</i> <i>The Friendly Stars.</i> Harper &amp; Brothers, New York, 1907.</p>
+
+<p>This book teaches you first the twenty brightest stars and then the
+constellations. I cannot say that this, or any other, is the "best
+book," but it has helped me most, and I suppose it is only natural that
+we should love best the first book that introduces us to a delightful
+subject.</p>
+
+<p>2. <i>Serviss.</i> <i>Astronomy with the Naked Eye.</i> Harper &amp; Brothers, New
+York, 1908.</p>
+
+<p>This teaches you the constellations first and the<span class='pagenum'><a name="Page_243" id="Page_243">[Pg 243]</a></span> brightest stars
+incidentally. Also it gives the old myths.</p>
+
+<p>3. <i>Serviss.</i> <i>Astronomy with an Opera-Glass.</i> D. Appleton &amp; Co., New
+York, 1906.</p>
+
+<p>4. <i>Serviss.</i> <i>Pleasures of the Telescope.</i> D. Appleton &amp; Co., New York,
+1905.</p>
+
+<p>5. <i>Milham.</i> <i>How to Identify the Stars.</i> The Macmillan Co., New York,
+1909.</p>
+
+<p>This gives a list of eighty-eight constellations, including thirty-six
+southern ones, and has tracings of twenty-eight.</p>
+
+<p>6. <i>Elson.</i> <i>Star Gazer's Handbook.</i> Sturgis &amp; Walton Co., New York,
+1909.</p>
+
+<p>About the briefest and cheapest. Has good charts and makes a specialty
+of the myths.</p>
+
+<p>7. <i>Serviss.</i> <i>Curiosities of the Sky.</i> Harper &amp; Brothers, New York.</p>
+
+<p>Tells about comets, asteroids, shooting stars, life on Mars, nebul&aelig;,
+temporary stars, coal-sacks, Milky Way, and other wonders.</p>
+
+<p>8. <i>Ball.</i> <i>Starland.</i> Ginn &amp; Co., Boston, New York, etc., 1899.</p>
+
+<p>This tells about a great many interesting experiments in astronomy that
+children can make.</p>
+
+<hr style='width: 45%;' />
+
+<p>If I had only a dollar or less to spend on astronomy I should buy a
+planisphere. I got mine from Thomas Whittaker, No. 2 Bible House, New
+York. It cost seventy-five cents, and will tell you where to find any
+star at any time in the year. It does<span class='pagenum'><a name="Page_244" id="Page_244">[Pg 244]</a></span> not show the planets, however. A
+planisphere that will show the planets costs about five dollars.
+However, there are only two very showy planets, viz., Venus and Jupiter.
+Any almanac will tell you (for nothing) when each of these is morning
+star, and when each of them is evening star.</p>
+
+<p>The best newspaper about stars, as far as I know, is a magazine called
+<i>The Monthly Evening Sky Map</i>, published by Leon Barritt, 150 Nassau
+St., New York. It costs a dollar a year. It gives a chart every month,
+showing all the planets, and all the constellations. Also it tells you
+about the interesting things, like comets, before they come.</p>
+
+<p>Good-bye. I hope you will never cease to learn about and love the earth
+and the sky. Perhaps you think you have learned a great deal already.
+But your pleasures have only begun. Wait till you learn about how the
+world began, the sun and all his planets, the distances between the
+stars, and the millions of blazing suns amid the Milky Way!</p>
+
+<div class='padding'>
+<p class='center'>THE END</p></div>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus244a_th.jpg" width="500" height="442" alt="THE SKY IN WINTER" title="" />
+<span class="caption">THE SKY IN WINTER</span>
+</div>
+
+<p><span class="smcap">Note.</span>&mdash;These simplified star maps are not as accurate as a planisphere,
+but they may be easier for children. All star maps are like ordinary
+maps, except that east and west are transposed. The reason for this is
+that you can hold a star map over your head, with the pole star toward
+the north, and the map will then match the sky. These maps contain some
+constellations that are only for grown-ups to study. The Winter
+constellations every child should know are:</p>
+
+<p>
+<span class="smcap">Auriga</span>, the Charioteer<br />
+<span class="smcap">Canis Major</span>, the Big Dog<br />
+<span class="smcap">Canis Minor</span>, the Little Dog<br />
+<span class="smcap">Cassiopeia</span>, the Queen in Her Chair<br />
+<span class="smcap">Cygnus</span>, the Swan<br />
+<span class="smcap">Leo</span>, the Lion<br />
+<span class="smcap">Orion</span>, the Hunter<br />
+<span class="smcap">Perseus</span>, Which Has the Arc<br />
+<span class="smcap">Taurus</span>, the Bull<br />
+<span class="smcap">Ursa Major</span>, the Great Bear<br />
+<span class="smcap">Ursa Minor</span>, the Little Bear<br />
+</p>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus244b_th.jpg" width="500" height="445" alt="THE SKY IN SPRING" title="" />
+<span class="caption">THE SKY IN SPRING</span>
+</div>
+
+<p><span class="smcap">Note.</span>&mdash;Once upon a time all the educated people spoke Latin. It was the
+nearest approach to a universal language. So most of the constellations
+have Latin names. The English, French and German names are all
+different, but if all children would learn the Latin names they could
+understand one another. The Spring constellations every child should
+know are:</p>
+
+<p>
+<span class="smcap">Leo</span>, the Lion<br />
+<span class="smcap">Lyra</span>, the Lyre<br />
+<span class="smcap">Cassiopeia</span>, the Queen in her Chair<br />
+<span class="smcap">Scorpio</span>, the Scorpion<br />
+<span class="smcap">Ursa Major</span>, the Great Bear<br />
+<span class="smcap">Ursa Minor</span>, the Little Bear<br />
+<span class="smcap">Virgo</span>, the Virgin<br />
+</p>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus244c_th.jpg" width="500" height="442" alt="THE SKY IN SUMMER" title="" />
+<span class="caption">THE SKY IN SUMMER</span>
+</div>
+
+<p><span class="smcap">Note.</span>&mdash;Every sky map is good for three months, in this way: If this is
+correct on June 1st at 10 P.M., it will be correct July 1st at 8 P.M.,
+and August 1st at 6 P.M. This is because the stars rise four minutes
+earlier every night. Thus, after thirty days, any star will rise thirty
+times four minutes earlier, or 120 minutes, or two hours. Children need
+not learn all the Summer constellations. The most interesting are:</p>
+
+<p>
+<span class="smcap">Auriga</span>, the Charioteer<br />
+<span class="smcap">Canis Major</span>, the Big Dog<br />
+<span class="smcap">Cygnus</span>, the Swan<br />
+<span class="smcap">Lyra</span>, the Lyre<br />
+<span class="smcap">Scorpio</span>, the Scorpion<br />
+</p>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/illus244d_th.jpg" width="500" height="442" alt="THE SKY IN AUTUMN" title="" />
+<span class="caption">THE SKY IN AUTUMN</span>
+</div>
+
+<p><span class="smcap">Note.</span>&mdash;This book tells how to find all the most interesting stars and
+constellations without maps, but many people prefer them. How to use
+star maps is explained under "The Sky in Winter." The Autumn
+constellations most interesting to children are:</p>
+
+<p>
+<span class="smcap">Aquila</span>, the Eagle<br />
+<span class="smcap">Auriga</span>, the Charioteer<br />
+<span class="smcap">Cassiopeia</span>, the Queen in Her Chair<br />
+<span class="smcap">Cygnus</span>, the Swan<br />
+<span class="smcap">Lyra</span>, the Lyre<br />
+<span class="smcap">Perseus</span>, Which Has the Arc<br />
+<span class="smcap">Taurus</span>, the Bull<br />
+<span class="smcap">Ursa Major</span>, the Great Bear<br />
+<span class="smcap">Ursa Minor</span>, the Little Bear<br />
+</p>
+
+<div class="figcenter" style="width: 500px;">
+<img src="images/endpaper_th.jpg" width="500" height="379" alt="" title="" />
+</div>
+
+<div class='trnote'>
+<p>Transcriber's notes</p>
+
+<p>
+Page <a href="#Page_124">124</a> "streams, runing" corrected to "streams, running"<br />
+Page <a href="#Page_127">127</a> "where he globe" corrected to "where the globe"<br />
+Page <a href="#Page_138">138</a> "ceatures to prove" corrected to "creatures to prove"<br />
+Page <a href="#Page_216">216</a> "this consellation is" corrected to "this constellation is"<br />
+Page <a href="#Page_203">203</a> "Everybirth day" corrected to "Every birthday"<br />
+</p>
+</div>
+
+
+
+
+
+
+
+
+
+<pre>
+
+
+
+
+
+End of the Project Gutenberg EBook of Earth and Sky Every Child Should Know, by 
+Julia Ellen Rogers
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+</body>
+</html>
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@@ -0,0 +1,6351 @@
+The Project Gutenberg EBook of Earth and Sky Every Child Should Know, by
+Julia Ellen Rogers
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Earth and Sky Every Child Should Know
+       Easy studies of the earth and the stars for any time and place
+
+Author: Julia Ellen Rogers
+
+Release Date: May 30, 2010 [EBook #32598]
+
+Language: English
+
+Character set encoding: ASCII
+
+*** START OF THIS PROJECT GUTENBERG EBOOK EARTH AND SKY ***
+
+
+
+
+Produced by Juliet Sutherland, Christine D. and the Online
+Distributed Proofreading Team at http://www.pgdp.net
+
+
+
+
+
+
+
+
+
+[Illustration: Pike's Peak, Colorado]
+
+  EARTH and SKY EVERY
+  CHILD SHOULD KNOW
+
+  EASY STUDIES OF THE EARTH AND THE
+  STARS FOR ANY TIME AND PLACE
+
+BY
+
+JULIA ELLEN ROGERS
+
+  AUTHOR OF
+  "THE TREE BOOK," "THE SHELL BOOK," "KEY TO THE NATURE
+  LIBRARY," "TREES EVERY CHILD SHOULD KNOW."
+
+  ILLUSTRATED BY
+  THIRTY-ONE PAGES OF PHOTOGRAPHS AND DRAWINGS
+
+[Illustration]
+
+  NEW YORK
+  GROSSET & DUNLAP
+  PUBLISHERS
+
+  COPYRIGHT, 1910, BY DOUBLEDAY, PAGE & COMPANY
+
+  PUBLISHED, OCTOBER, 1910
+
+  ALL RIGHTS RESERVED, INCLUDING THAT OF TRANSLATION
+  INTO FOREIGN LANGUAGES, INCLUDING THE SCANDINAVIAN
+
+
+
+
+ACKNOWLEDGMENTS
+
+
+A number of the photographs in this volume are used by permission of the
+American Museum of Natural History. The star maps and drawings of the
+constellations are by Mrs. Jerome B. Thomas. The poem by Longfellow,
+quoted in part, is with the permission of the publishers, Houghton,
+Mifflin & Co.
+
+       *       *       *       *       *
+
+
+
+
+CONTENTS
+
+
+  _PART I. THE EARTH_
+
+  PAGE
+
+  THE GREAT STONE BOOK                                          3
+
+  THE FOSSIL FISH                                               6
+
+  THE CRUST OF THE EARTH                                        9
+
+  WHAT IS THE EARTH MADE OF?                                   14
+
+  THE FIRST DRY LAND                                           22
+
+  A STUDY OF GRANITE                                           27
+
+  METAMORPHIC ROCKS                                            31
+
+  THE AIR IN MOTION                                            35
+
+  THE WORK OF THE WIND                                         44
+
+  RAIN IN SUMMER, _by Henry W. Longfellow_                     50
+
+  WHAT BECOMES OF THE RAIN?                                    51
+
+  THE SOIL IN FIELDS AND GARDENS                               58
+
+  THE WORK OF EARTHWORMS                                       63
+
+  QUIET FORCES THAT DESTROY ROCKS                              68
+
+  HOW ROCKS ARE MADE                                           72
+
+  GETTING ACQUAINTED WITH A RIVER                              78
+
+  THE WAYS OF RIVERS                                           84
+
+  THE STORY OF A POND                                          90
+
+  THE RIDDLE OF THE LOST ROCKS                                 93
+
+  THE QUESTION ANSWERED                                        96
+
+  GLACIERS AMONG THE ALPS                                      98
+
+  THE GREAT ICE SHEET                                         104
+
+  FOLLOWING SOME LOST RIVERS                                  110
+
+  THE MAMMOTH CAVE OF KENTUCKY                                114
+
+  LAND BUILDING BY RIVERS                                     121
+
+  THE MAKING OF MOUNTAINS                                     126
+
+  THE LAVA FLOOD OF THE NORTHWEST                             130
+
+  THE FIRST LIVING THINGS                                     134
+
+  AN ANCIENT BEACH AT EBB TIDE                                138
+
+  THE LIME ROCKS                                              147
+
+  THE AGE OF FISHES                                           152
+
+  KING COAL                                                   155
+
+  HOW COAL WAS MADE                                           160
+
+  THE MOST USEFUL METAL                                       167
+
+  THE AGE OF REPTILES                                         175
+
+  THE AGE OF MAMMALS                                          180
+
+  THE HORSE AND HIS ANCESTORS                                 186
+
+  THE AGE OF MAN                                              194
+
+
+  _PART II. THE SKY_
+
+  EVERY FAMILY A "STAR CLUB"                                  201
+
+  THE DIPPERS AND THE POLE STAR                               207
+
+  CONSTELLATIONS YOU CAN ALWAYS SEE                           213
+
+  WINTER CONSTELLATIONS                                       219
+
+  ORION, HIS DOGS, AND THE BULL                               223
+
+  SEVEN FAMOUS CONSTELLATIONS                                 231
+
+  THE TWENTY BRIGHTEST STARS                                  239
+
+  HOW TO LEARN MORE                                           241
+
+
+
+
+ILLUSTRATIONS
+
+
+  Pike's Peak                                               _Frontispiece_
+
+                                                               FACING PAGE
+
+  Sand Dunes in Arizona                                                 44
+
+  Grand Canon of the Colorado                                           45
+
+  Castles Carved by Rain and Wind                                       52
+
+  Where All the Water Comes From                                        53
+
+  The Richest Gold and Silver Mines                                     72
+
+  Rocks Being Ground to Flour                                           73
+
+  A Pond Made by a Glacier                                              88
+
+  The Struggle Between a Stream and Its
+  Banks                                                                 89
+
+  Ripple Marks and Glacial Striae                                       102
+
+  Glacial Grooves and Markings                                         103
+
+  Crinoid and Ammonite                                                 140
+
+  Fossil Corals, Coquina, Hippurite Limestone                          141
+
+  Fossil Fish                                                          152
+
+  Meteorite                                                            153
+
+  Eocene Fish and Trilobite                                            156
+
+  How Coal Was Made                                                    157
+
+  Banded Sandstone. Opalized Wood                                      176
+
+  Allosaurus                                                           177
+
+  A Three-horned Dinosaur                                              178
+
+  Remains of Brontosaurus                                              179
+
+  Restoration of Brontosaurus                                          182
+
+  Ornitholestes, a Small Dinosaur                                      183
+
+  A Mammoth                                                            186
+
+  An Ancestor of the Horse                                             187
+
+  Orion, His Dogs, and the Bull                                        214
+
+  Other Fanciful Sketches of Constellations                            215
+
+  The Sky in Winter                                                    244
+
+  The Sky in Spring                                                    244
+
+  The Sky in Summer                                                    244
+
+  The Sky in Autumn                                                    244
+
+
+
+
+PART I
+
+THE EARTH
+
+       *       *       *       *       *
+
+
+
+
+THE GREAT STONE BOOK
+
+    "The crust of our earth is a great cemetery where the rocks
+    are tombstones on which the buried dead have written their
+    own epitaphs. They tell us who they were, and when and where
+    they lived."--_Louis Agassiz._
+
+
+Deep in the ground, and high and dry on the sides of mountains, belts of
+limestone and sandstone and slate lie on the ancient granite ribs of the
+earth. They are the deposits of sand and mud that formed the shores of
+ancient seas. The limestone is formed of the decayed shells of animal
+forms that flourished in shallow bays along those shores. And all we
+know about the life of these early days is read in the epitaphs written
+on these stone tables.
+
+Under the stratified rocks, the granite foundations tell nothing of life
+on the earth. But the sea rolled over them, and in it lived a great
+variety of shellfish. Evidently the earliest fossil-bearing rocks were
+worn away, for the rocks that now lie on the granite show not the
+beginnings, but the high tide of life. The "lost interval" of which
+geologists speak was a time when living forms were few in the sea.
+
+In the muddy bottoms of shallow, quiet bays lie the shells and skeletons
+of the creatures that live their lives in those waters and die when they
+grow old and feeble. We have seen the fiddler crabs by thousands on
+such shores, young and old, lusty and feeble. We have seen the rocks
+along another coast almost covered by the coiled shells of little gray
+periwinkles, and big clumps of black mussels hanging on the piers and
+wharfs. All these creatures die, at length, and their shells accumulate
+on the shallow sea bottom. Who has not spent hours gathering dead shells
+which the tide has thrown up on the beach? Who has not cut his foot on
+the broken shells that lie in the sandy bottom we walk on whenever we go
+into the surf to swim or bathe?
+
+Read downward from the surface toward the earth's centre--
+
+
+TABLE OF CONTENTS
+
+
+  ------+----------------------+-----------+-----------------------
+  Part  | _Rock Systems_       | _Dominant | _Dominant Plants_
+        |                      | Animals_  |
+  ------+----------------------+-----------+-----------------------
+   VII. | Recent               | Man       | Flowering kinds
+        |{ Quaternary          |           |
+    VI. |           { Pliocene | Mammals   | Early flowering
+        |{ Tertiary { Miocene  |           |
+        |           { Eocene   |           |
+     V. | Mesozoic             | Reptiles  | Cycads
+    IV. | Carboniferous        | Amphibians| Ferns and Conifers
+   III. | Devonian             | Fishes    | Ferns
+    II. | Silurian             | Molluscs  | Seaweeds
+     I. | Fire-formed          | No life   | No life
+  ------+----------------------+-----------+-----------------------
+
+It is by dying that the creatures of the sea write their epitaphs. The
+mud or sand swallows them up. In time these submerged banks may be left
+dry, and become beds of stone. Then some of the skeletons and shells
+may be revealed in blocks of quarried stone, still perfect in form after
+lying buried for thousands of years.
+
+The leaves of this great stone book are the layers of rock, laid down
+under water. Between the leaves are pressed specimens--fossils of
+animals and plants that have lived on the earth.
+
+
+
+
+THE FOSSIL FISH
+
+
+I remember seeing a flat piece of stone on a library table, with the
+skeleton of a fish distinctly raised on one surface. The friend who
+owned this strange-looking specimen told me that she found it in a stone
+quarry. She brought home a large piece of the slate, and a stone-mason
+cut out the block with the fish in it, and her souvenir made a useful
+and interesting paper-weight.
+
+The story of that fish I heard with wonder, and have never forgotten. I
+had never heard of fossil animals or plants until my good neighbour
+talked about them. She showed me bits of stone with fern leaves pressed
+into them. One piece of hard limestone was as full of little sea-shells
+as it could possibly be. One ball of marble was a honeycombed pattern,
+and called "fossil coral."
+
+The fossil fish was once alive, swimming in the sea, and feeding on the
+things it liked to eat, as all happy fishes do. Near shore a river
+poured its muddy water into the sea, and the sandy bottom was covered
+with the mud that settled on it. At last the fish grew old, and perhaps
+a trifle stupid about catching minnows. It died, and sank to the muddy
+floor of the sea. Its horny bones were not dissolved by the water. They
+remained, and the mud filtered in and filled all the spaces. Soon the
+fish was buried completely by the sediment the river brought.
+
+Years, thousands of them, went by, and the layer of mud was so thick and
+heavy above the skeleton of the fish that it bore a weight of tons
+there, under the water. The close-packed mud became a stiff clay. After
+more thousands of years, the sea no longer came so far ashore, for the
+river had built up a great delta of land out of mud. The clay in which
+the fish was hidden hardened into slate. Water crept down in the loose
+upper layers, dissolving out salt and other minerals, and having harder
+work to soak through, the lower it went. The water left some of the
+minerals it had accumulated, calcium and silica and iron, in the lower
+rock beds, making them harder than they were before, and heavier and
+less porous.
+
+When the river gorge was cut through these layers of rock, the colour
+and thickness of each kind were laid bare. Centuries after, perhaps
+thousands of years, indeed, the quarrymen cut out the layers fit for
+building stones, flags for walks and slates for roofing. In the
+splitting of a flagstone, the long-buried skeleton of the fish came to
+light.
+
+Under our feet the earth lies in layers. Under the soil lie loose beds
+of clay and sand and gravel, and under these loose kinds of earth are
+close-packed clays, sandstones, limestones, shales, often strangely
+tilted away from the horizontal line, but variously fitted, one layer to
+another. Under these rocks lie the foundations of the earth--the
+fire-formed rocks, like granite. The depth of this original rock is
+unknown. It is the substance out of which the earth is made, we think.
+All the layered rocks are made of particles of the older ones, stolen by
+wind and water, and finally deposited on the borders of lakes and seas.
+So our rivers are doing to-day what they have always done--they are
+tearing down rocks, grinding and sifting the fragments, and letting them
+fall where the current of fresh water meets a great body of water that
+is still, or has currents contrary to that of the river.
+
+Do you see a little dead fish in the water? It is on the way to become a
+fossil, and the mud that sifts over it, to become a layer of slate.
+Every seashore buries its dead in layers of sand and mud.
+
+
+
+
+THE CRUST OF THE EARTH
+
+
+It is hard to believe that our solid earth was once a ball of seething
+liquid, like the red-hot iron that is poured out of the big clay cups
+into the sand moulds at an iron foundry. But when a mountain like
+Vesuvius sets up a mighty rumbling, and finally a mass of white-hot lava
+bursts from the centre and streams down the sides, covering the
+vineyards and olive orchards, and driving the people out of their homes
+in terror, it seems as if the earth's crust must be but a thin and frail
+affair, covering a fiery interior, which might at any time break out.
+The people who live near volcanoes might easily get this idea.
+
+But they do not. They go back as soon as the lava streams are cooled,
+and rebuild their homes, and plant more orchards and vineyards. "It is
+_so_ many years," say they to one another, "since the last bad eruption.
+Vesuvius will probably sleep now till we are dead and gone."
+
+This is good reasoning. There are few active volcanoes left on the
+earth, compared with the number that were once active, and long ago
+became extinct. And the time between eruptions of the active ones grows
+longer; the eruptions less violent. Terrible as were the recent
+earthquakes of San Francisco and Messina, this form of disturbance of
+the earth's crust is growing constantly less frequent. The earth is
+growing cooler as it grows older; the crust thickens and grows stronger
+as centuries pass. We have been studying the earth only a few hundred
+years. The crust has been cooling for millions of years, and
+mountain-making was the result of the shrinking of the crust. That
+formed folds and clefts, and let masses of the heated substance pour out
+on the surface.
+
+My first geography lesson I shall never forget. The new teacher had very
+bright eyes and _such_ pretty hands! She held up a red apple, and told
+us that the earth's substance was melted and burning, inside its crust,
+which was about as thick, in proportion to the size of the globe, as the
+skin of the apple. I was filled with wonder and fear. What if we
+children jumped the rope so hard as to break through the fragile shell,
+and drop out of sight in a sea of fiery metal, like melted iron? Some of
+the boys didn't believe it, but they were impressed, nevertheless.
+
+The theory of the heated interior of the earth is still believed, but
+the idea that flames and bubbling metals are enclosed in the outer layer
+of solid matter has generally been abandoned. The power that draws all
+of its particles toward the earth's centre is stated by the laws of
+gravitation. The amount of "pull" is the measure of the weight of any
+substance. Lift a stone, and then a feather pillow, much larger than
+the stone. One is strongly drawn to the earth; the other not. One is
+_heavy_, we say, the other _light_.
+
+If a stone you can pick up is heavy, how much heavier is a great boulder
+that it takes a four-horse team to haul. What tremendous weight there is
+in all the boulders scattered on a hillside! The hill itself could not
+be made level without digging away thousands of tons of earth. The
+earth's outer crust, with its miles in depth of mountains and level
+ground, is a crushing weight lying on the heated under-substance. Every
+foot of depth adds greatly to the pressure exerted upon the mass, for
+the attraction of gravitation increases amazingly as the centre of the
+earth is approached.
+
+It is now believed that the earth is solid to its centre, though heated
+to a high degree. Terrific pressure, which causes this heat, is exerted
+by the weight of the crust. A crack in the crust may relieve this
+pressure at some point, and a mass of substance may be forced out and
+burst into a flaming stream of lava. Such an eruption is familiar in
+volcanic regions. The fact that red-hot lava streams from the crater of
+Vesuvius is no proof that it was seething and bubbling while far below
+the surface.
+
+Volcanoes, geysers, and hot springs prove that the earth's interior is
+hot. The crust is frozen the year around in the polar regions, and never
+between the Tropics of Cancer and Capricorn. The sun's rays produce our
+different climates, but they affect only the surface. Underground, there
+is a rise of a degree of temperature for every fifty feet one goes
+down. The lowest mine shaft is about a mile deep. That is only one
+four-thousandth of the distance to the earth's centre.
+
+By an easy computation we could locate the known melting-point for
+metals and other rock materials. But one degree for each fifty feet of
+depth below the surface may not be correct for the second mile, as it is
+for the first. Again, the melting-point is probably a great deal higher
+for substances under great pressure. The weight of the crust is a burden
+the under-rocks bear. Probably the pressure on every square inch reaches
+thousands of tons. Could any substance become liquid with such a weight
+upon it, whatever heat it attained? Nobody can answer this question.
+
+The theory that volcanoes are chimneys connecting lakes of burning lava
+with the surface of the earth is discredited by geologists. The weight
+of the overlying crust would, they think, close such chambers, and
+reduce liquids to a solid condition.
+
+Since the first land rose above the sea, the crust of the earth has
+gradually become more stable, but even now there is scarcely a day when
+the instruments called seismographs do not record earthquake shocks in
+some part of the earth; and the outbreaks of Vesuvius and AEtna, the
+constant boiling of lava in the craters of the Hawaiian Islands and
+other volcanic centres, prove that even now the earth's crust is very
+thin and unstable. The further back in time we go, the thinner was the
+crust, the more frequent the outbursts of volcanic activity, the more
+readily did wrinkles form.
+
+The shores of New Jersey and of Greenland are gradually sinking, and the
+sea coming up over the land. Certain parts of the world are gradually
+rising out of the sea. In earlier times the rising or the sinking of
+land over large areas happened much more frequently than now.
+
+
+
+
+WHAT IS THE EARTH MADE OF?
+
+
+"Baking day" is a great institution in the comfortable farm life of the
+American people. The big range oven is not allowed to grow cold until
+rows of pies adorn the pantry shelves, and cakes, tarts, and generous
+loaves of bread are added to the store. Cookies, perhaps, and a big pan
+full of crisp, brown doughnuts often crown the day's work. No gallery of
+art treasures will ever charm the grown-up boys and girls as those
+pantry shelves charmed the bright-eyed, hungry children, who were
+allowed to survey the treasure-house, and sample its good things while
+they were still warm.
+
+You could count a dozen different kinds of cakes and pies, rolls and
+cookies on those pantry shelves, yet several of them were made out of
+the same dough. Instead of a loaf of bread, mother could make two or
+three kinds of coffee cake, or cinnamon rolls, or currant buns, or
+Parker-House rolls. Even the pastry, which made the pies and tarts, was
+not so different from the bread dough, for each was made of flour, and
+contained, besides the salt, "shortening," which was butter or lard.
+Sugar was used in everything, from the bread, which had a
+table-spoonful, to the cookies, which were finished with a sifting of
+sugar on top.
+
+How much of the food we eat is made of a very few staple
+foodstuffs,--starch, sugar, fats! So in the wonderful earth and all that
+grows out of it and lives upon it. Only seventy different elements have
+been discovered, counting, besides the earth, the water and the air, and
+even the strange wandering bodies, called meteorites, that fall upon the
+earth out of the sky. Like the flour in the different cakes and pies,
+the element carbon is found in abundance and in strangely different
+combinations. As a gas, in combination with oxygen, it is breathed out
+of our lungs, and out of chimneys where coal and wood are burned. It
+forms a large part of the framework of trees and other plants, and
+remains as charcoal when the wood is slowly burned under a close
+covering. There is a good proportion of carbon in animal bodies, in the
+bones as well as the soft parts, and carbon is plentiful in the mineral
+substances of the earth.
+
+The chemist is the man who has determined for us the existence and the
+distribution of the seventy elements. He finds them in the solid
+substances of the globe and in the water that covers four-fifths of its
+surface; in the atmosphere that covers sea and land, and in all the
+living forms of plants and animals that live in the seas and on the
+land. By means of an instrument called the spectroscope, the heavenly
+bodies are proved to be made of the same substances that are found in
+the rocks. The sun tells what it is made of, and one proof that the
+earth is a child of the sun is in the fact that the same elements are
+found in the substance of both.
+
+Of the seventy elements, the most important are these: Oxygen, silicon,
+aluminum, iron, manganese, calcium, magnesium, potassium, sodium,
+carbon, hydrogen, phosphorus, sulphur, chlorine, nitrogen.
+
+_Oxygen_ is the most plentiful and the most important element. One-fifth
+of the air we breathe is oxygen; one-third of the water we drink. The
+rock foundations of the earth are nearly one-half oxygen. No fire can
+burn, no plant or animal can grow, or even decay after it dies, unless
+oxygen is present and takes an active part in each process. Strangely
+enough, this wonderful element is invisible. We open a window, and pure
+air, rich in oxygen, comes in and takes the place of the bad air but we
+cannot see the change. Water we see, but if the oxygen and the hydrogen
+which compose the colourless liquid were separated, each would become at
+once an invisible gas. The oxygen of solid rocks exists only in
+combination with other elements.
+
+_Silicon_ is the element which, united with oxygen, makes the rock
+called quartz. On the seashore the children are busy with their pails
+and shovels digging in the white, clean sand. These grains are of
+quartz,--fine crystals of a rock which forms nearly three-quarters of
+the solid earth's substance. Not only in rocks, but out here in the
+garden, the soil is full of particles of sand. You cannot get away from
+it.
+
+_Aluminum_ is a light, bluish-white metal which we know best in
+expensive cooking utensils. It is more abundant even than iron, but
+processes of extracting it from the clay are still expensive. It is
+oftenest found in combination with oxygen and silicon. While nearly
+one-tenth of the earth's crust is composed of the metal aluminum,
+four-fifths and more is composed of the minerals called silicates of
+aluminum--oxygen, silicon, and aluminum in various combinations. It is
+more plentiful than any other substance in rocks and in the clays and
+ordinary soils, which are the finely ground particles of rock material.
+
+_Iron_ is one of the commonest of elements. We know it by its red
+colour. A rusty nail is covered with oxide of iron, a combination which
+is readily formed wherever iron is exposed to the action of water or
+air. You have seen yellowish or red streaks in clefts of the rocks. This
+shows where water has dissolved out the iron and formed the oxide. The
+red colour of New Jersey soil is due to the iron it contains. Indeed,
+the whole earth's crust is rich in iron which the water easily
+dissolves. The roots of plants take up quantities of iron in solution
+and this mounts to the blossoms, leaves, and fruit. The red or yellow
+colour of autumn leaves, of apples, of strawberries, of tulips, and of
+roses, is produced by iron. The rosy cheeks of children are due to iron
+in the food they eat and in the water they drink. The doctor but follows
+the suggestion of nature when he gives a pale and listless person a
+tonic of iron to make his blood red.
+
+Iron is rarely found free, but it forms about five per cent. of the
+crust of the earth, and it is believed to form at least one-fifth of the
+unknown centre of the earth, the bulk of the globe, the weight of which
+we know, but concerning the substance of which we can say little that is
+positive.
+
+_Manganese_ is not a conspicuous element, but is found united with
+oxygen in purplish or black streaks on the sides of rocks. It is
+somewhat like iron, but much less common.
+
+_Calcium_ is the element that is the foundation of limestones. The
+skeletons and shells of animals are made of calcite, a common mineral
+formed by the uniting of carbon, oxygen, and calcium. Marbles are,
+perhaps, the most permanent form of the limestone rocks. "Hard" water
+has filtered through rocks containing calcite, and absorbed particles of
+this mineral. From water thus impregnated, all animal life on the earth
+obtains its bone-building and shell-building materials.
+
+_Carbon_ forms a large part of the tissues of plants and animals, and in
+the remains of these it is chiefly found in the earth's crust. When
+these burn or decay, the carbon remains as charcoal or escapes to the
+air in union with oxygen as the well known carbonic acid gas. This is
+one of the most important foods of plants. Joined with calcium it forms
+the mineral calcite, or carbonate of lime.
+
+_Hydrogen_ is one of the two gases that unite to form water. Oxygen is
+the other. Many kinds of rock contain a considerable amount of water.
+Surface water sinks into porous soils and rocks, and accumulates in
+pockets and veins which feed springs, and are the reserve water supply
+that keeps our rivers flowing, even through dry weather. More water is
+held by absorption in the earth's solid crust than in all the oceans and
+seas and great lakes.
+
+Hydrogen, combined with carbon, occurs in solid rocks where the remains
+of plants and animals have slowly decayed. From such processes the
+so-called hydrocarbons, rock oil and natural gas, have accumulated. When
+such decay goes on above ground, these valuable products escape into the
+air. Marsh gas, whose feeble flame above decaying vegetation is the
+will-o'-the-wisp of swamps, is an example.
+
+_Magnesium_, _potassium_, and _sodium_ are found in equal quantities in
+the earth's crust, but never free. In union with chlorine, each forms a
+soluble salt, and is thus found in water. Common salt, chloride of
+sodium, is the most abundant of these. Water dissolves salt out of the
+rocks, and carries it into the sea. Clouds that rise by the evaporation
+of ocean water leave the salt behind, hence the seas are becoming more
+and more salty, for the rivers carry salt to the oceans, which hold fast
+all they get.
+
+_Phosphorus_ is an element found united with oxygen in the tissues of
+both plants and animals. It is most abundant in bones. Rocks containing
+fossil bones are rich in lime phosphates, which are important commercial
+fertilizers for enriching the soil. Beds of these rocks are found and
+mined in South Carolina and elsewhere.
+
+_Sulphur_ is well known as a yellow powder found most plentifully in
+rocks that are near volcanoes. It is a needed element in plant and
+animal bodies. It occurs in rocks, united with many different elements.
+In union with oxygen and a metal it forms the group of minerals called
+sulphates. In union with iron it forms sulphide of iron. The "fool's
+gold" which Captain John Smith's colonists found in the sand at
+Jamestown, was this worthless iron pyrites.
+
+_Chlorine_ is a greenish, yellow gas, very heavy, and dangerous to
+inhale. If it gets into the lungs, it settles into the lowest levels,
+and one must stand on one's head to get it out. As an element of the
+earth's crust it is not very plentiful, but it is a part of all the
+chlorides of sodium, magnesium, and potassium. In salt, it forms two per
+cent. of the sea water. It is much less abundant in the rocks.
+
+To these elements we might add _nitrogen_, that invisible gas which
+forms nearly four-fifths of our atmosphere, and is a most important
+element of plant food in the soil. Most of the seventy elements are very
+rare. Many are metals, like gold and iron and silver. Some are not
+metals. Some are solid. A few are liquid, like the metal mercury, and
+several are gaseous. Some are free and pure, and show no disposition to
+unite with others. Nuggets of gold are examples of this. Some exist only
+in union with other elements. This is the common rule among the
+elements. Changes are constantly going on. The elements are constantly
+abandoning old partnerships and forming new ones. Growth and decay of
+plant and animal life are but parts of the great programme of constant
+change which is going on and has been in progress since the world
+began.
+
+
+
+
+THE FIRST DRY LAND
+
+
+When the earth's crust first formed it was still hot, though not so hot
+as when it was a mass of melted, glowing substance. As it moved through
+the cold spaces of the sky, it lost more heat and its crust became
+thicker. At length the cloud masses became condensed enough to fall in
+torrents of water, and a great sea covered all the land. This was before
+any living thing, plant or animal, existed on our planet. Can you
+imagine the continents and islands that form the land part of a map or
+globe suddenly overwhelmed by the oceans, the names and boundaries of
+which you have taken such pains to learn in the study of geography? The
+globe would be one blank of blue water, and geography would be
+abolished--and there would be nobody to study it. Possibly the fishes in
+the sea might not notice any change in the course of their lives, except
+when they swam among the ruins of buried cities and peered into the
+windows of high buildings, or wondered what new kind of seaweed it was
+when they came upon a submerged forest.
+
+In that old time of the great sea that covered the globe, we are told
+that there was a dense atmosphere over the face of the deep. So things
+were shaping themselves for the far-off time when life should exist,
+not only in the sea, where the first life did appear, but on land. But
+it took millions of years to fit the earth for living things.
+
+The cooling of the earth made it shrink, and the crust began to be
+folded into gentle curves, as the skin of a shrunken apple becomes
+wrinkled on the flesh. Some of these creases merely changed the depth of
+water on the sea bottom; but one ridge was lifted above the water. The
+water parted and streamed down its sloping sides, and a granite reef,
+which shone in the sunshine, became the first dry land. It lay east and
+west, and stretched for many miles. It is still dry land and is a part
+of our own continent. Now it is but a small part of the country, but it
+is known by geologists, who can tell its boundaries, though newer land
+joins it on every side. It is named the Laurentian Hills, on geological
+maps. Its southern border reaches along the northern boundary of the
+Great Lakes to the head-waters of the Mississippi River.
+
+From this base, two ridges are lifted, forming a colossal V. One extends
+northeast to Nova Scotia; the other northwest to the Arctic seas. The V
+encloses Hudson Bay.
+
+Besides this first elongated island of bare rocks, land appeared in a
+strip where now the Blue Ridge Mountains stretch from New England to
+Georgia. The other side of the continent lifted up two folds of the
+crust above sea level. They are the main ridges of the Colorado and the
+Wasatch Mountains. Possibly the main ridge of the Sierra Nevada rose
+also at this time. The Ozark group of mountains, too, showed as a few
+island peaks above the sea.
+
+These first rocks were rapidly eaten away, for the atmosphere was not
+like ours, but heavily charged with destructive gases, which did more,
+we believe, to disintegrate the exposed rock surfaces than did the two
+other forces, wind and water, combined. The sediment washed down to the
+sea by rains, accumulated along the shores, filling the shallows and
+thus adding to the width of the land areas. The ancient granite ridge of
+the Laurentian Hills is now low, and slopes gently. This is true of all
+very old mountains. The newer ones are high and steep. It takes time to
+grind down the peaks and carry off the waste material loosened by
+erosion.
+
+Far more material than could have been washed down the slopes of the
+first land ridges came directly from the interior of the earth, and
+spread out in vast, submarine layers upon the early crust. Volcanic
+craters opened under water, and poured out liquid mineral matter, that
+flowed over the sea bottom before it cooled. Imagine the commotion that
+agitated the water as these submerged chimneys blew off their lids, and
+discharged their fiery contents! It was long before the sea was cool
+enough to be the home of living things.
+
+The layers of rock that formed under the sea during this period of the
+earth's history are of enormous thickness. They were four or five miles
+deep along the Laurentian Hills. They broadened the original granite
+ridge by filling the sea bottom along the shores. The backbones of the
+Appalachian system and the Cordilleras were built up in the same
+way--the oldest rocks were worn away, and their debris built up newer
+ones in strata.
+
+When these layers of rock became dry land, the earth's crust was much
+more stable and cool than it had ever been before. The vast
+rock-building of that era equals all that has been done since. The
+layers of rocks formed since then do not equal the total thickness of
+these first strata. So we believe that the time required to build those
+Archaean rock foundations equals or surpasses the vast period that has
+elapsed since the Archaean strata were formed.
+
+The northern part of North America has grown around those old granite
+ridges by the gradual rising of the shores. The geologist may walk along
+the Laurentian Hills, that parted the waters into a northern and a
+southern ocean. He crosses the rocky beds deposited upon the granite;
+then the successive beds formed as the land rose and the ocean receded.
+Age after age is recorded in the rocks. Gradually the sea is crowded
+back, and the land masses, east, west, and north, meet to form the
+continent. Nowhere on the earth are the steps of continental growth
+shown in unbroken sequence as they are in North America.
+
+How long ago did those first islands appear above the sea? Nobody
+ventures a definite answer to this question. No one has the means of
+knowing. But those who know most about it estimate that at the least one
+hundred million years have passed since then--one hundred thousand
+thousand years!
+
+
+
+
+A STUDY OF GRANITE
+
+
+In Every village cemetery it is easy to find shafts of gray or speckled
+granite, the polished surfaces of which show that the granite is made of
+small bits of different coloured minerals, cemented together into solid
+rock. Outside the gate you will usually find a place where monuments and
+gravestones may be bought. Here there is usually a stonecutter chipping
+away on a block with his graving tools. He is a man worth knowing, and
+because his work is rather monotonous he will probably be glad to talk
+to a chance visitor and answer questions about the different kinds of
+stone on which he works.
+
+There are bits of granite lying about on the ground. If you have a
+hand-glass of low power, such as the botany class uses to examine the
+parts of flowers, it will be interesting to look through it and see the
+magnified surface of a flake of broken granite. Here are bits of glassy
+quartz, clear and sparkling in the sun. Black and white may be all the
+colours you make out in this specimen, or it may be that you see specks
+of pink, dark green, gray, and smoky brown, all cemented together with
+no spaces that are not filled. The particles of quartz are of various
+colours, and are very hard. They scratch glass, and you cannot scratch
+them with the steel point of your knife, as you can scratch the other
+minerals associated with the grains of quartz.
+
+Granite is made of quartz, feldspar, and mica, sometimes with added
+particles of hornblende. Feldspar particles have as wide a range of
+colour as quartz, but it is easy to tell the two apart. A knife will
+scratch feldspar, as it is not so hard as quartz. The crystals of
+feldspar have smooth faces, while quartz breaks with a rough surface as
+glass does. Feldspar loses its glassy lustre when exposed to the
+weather, and becomes dull, with the soft lustre of pearl.
+
+Mica may be clear and glassy, and it ranges in colour from transparency
+through various shades of brown to black. It has the peculiarity of
+splitting into thin, leaf-like, flexible sheets, so it is easy to find
+out which particles in a piece of granite are mica. One has only to use
+one's pocket knife with a little care. Hornblende is a dark mineral
+which contains considerable iron. It is found in lavas and granites,
+where it easily decays by the rusting of the iron. It is not unusual to
+see a rough granite boulder streaked with dark red rust from this cause.
+
+The crumbling of granite is constantly going on as a result of the
+exposure of its four mineral elements to the air. Quartz is the most
+stable and resistant to weathering. Soil water trickling over a granite
+cliff has little effect on the quartz particles; but it dissolves out
+some of the silicon. The bits of feldspar are even more resistant to
+water than quartz is, but the air causes them to decay rapidly, and
+finally to fall away in a sort of mealy clay. Mica, like feldspar,
+decays easily. Its substance is dissolved by water and carried away to
+become a kind of clay. The hornblende rusts away chiefly under the
+influence of moist air and trickling water.
+
+We think of granite as a firm, imperishable kind of rock, and use it in
+great buildings like churches and cathedrals that are to stand for
+centuries. But the faces that are exposed to the air suffer, especially
+in regions having a moist climate. The signs of decay are plainly
+visible on the outer surfaces of these stones. Fortunate it is that the
+weathering process cannot go very deep.
+
+The glassy polish on a smooth granite shaft is the silicon which acts as
+a cement to bind all the particles together. It is resistant to the
+weather. A polished shaft will last longer than an unpolished one.
+
+Granites differ in colouring because the minerals that compose them, the
+feldspars, quartzes, micas, and hornblendes, have each so wide a range
+of colour. Again, the proportions of the different mineral elements vary
+greatly in different granites. A banded granite the colours of which
+give it a stratified appearance is called a gneiss.
+
+We have spoken before of the seventy elements found in the earth's
+crust. A mineral is a union of two or more of these different elements;
+and we have found four minerals composing our granite rock. It may be
+interesting to go back and inquire what elements compose these four
+minerals. Quartz is made of silicon and oxygen. Feldspar is made of
+silicon, oxygen, and aluminum. Mica is made of silicon, oxygen, and
+carbon, with some mingling of potassium and iron and other elements in
+differing proportions. Hornblende is made of silicon, oxygen, carbon,
+and iron.
+
+The crumbling of a granite rock separates the minerals that compose it,
+reducing some to the condition of clay, others to grains of sand. Some
+of the elements let go their union and become free to form new unions.
+Water and wind gather up the fragments of crumbling granite and carry
+them away. The feldspar and mica fragments form clay; the quartz
+fragments, sand. All of the sandstones and slates, the sand-banks and
+sand beaches, are made out of crumbled granite, the rocky foundations of
+the earth.
+
+
+
+
+METAMORPHIC ROCKS
+
+
+In the dawn of life on the earth, soft-bodied creatures, lowest in the
+scale of being, inhabited the sea. The ancient volcanoes the
+subterranean eruptions of which had spread layers of mineral substance
+on the ocean floor, and heated the water to a high degree, had subsided.
+The ocean was sufficiently cool to maintain life. The land was being
+worn down, and its debris washed into the ocean. The first sand-banks
+were accumulating along sandy shores. The finer sediment was carried
+farther out and deposited as mud-banks. These were buried under later
+deposits, and finally, by the rising of the earth's crust, they became
+dry land. Time and pressure converted the sand-banks into sandstones;
+the mud-banks into clay. The remains of living creatures utterly
+disappeared, for they had no hard parts to be preserved as fossils.
+
+The shrinking of the earth's crust had crumpled into folds of the utmost
+complexity those horizontal layers of lava rock poured out on the ocean
+floor. Next, the same forces attacked the thick rock layers formed out
+of sediment--the aqueous or water-formed sandstones and clays.
+
+The core of the globe contracts, and the force that crumples the crust
+to fit the core generates heat. The alkaline water in the rocks joins
+with the heat produced by the crumpling and crushing forces, acting
+downward, and from the sides, to transform pure sandstone into glassy
+quartzite, and clay into slate. In other words, water-formed rocks are
+baked until they become fire-formed rocks. They are what the geologist
+calls _metamorphic_, which means _changed_.
+
+In many mountainous regions there are breaks through the strata of
+sandstone and slates and limestones, through which streams of lava have
+poured forth from the heated interior. Along the sides of these fissures
+the hot lava has changed all the rocks it touched. The heat of the
+volcanic rock matter has melted the silica in the sand, which has
+hardened again into a crystalline substance like glass.
+
+Have you ever visited a brick-yard? Here men are sifting clay dug out of
+a pit or the side of a hill, adding sand from a sand-bank, and in a big
+mixing box, stirring these two "dry ingredients" with water into a thick
+paste. This dough is moulded into bricks, sun-dried, and then baked in
+kilns themselves built of bricks. At the end of the baking, the soft,
+doughy clay block is transformed into a hard, glassy, or dull brick.
+From aqueous rock materials, fire has produced a metamorphic rock.
+Volcanic action is imitated in this common, simple process of
+brickmaking.
+
+Milwaukee brick is made of clay that has no iron in it. For this reason
+the bricks are yellow after baking. Most bricks are red, on account of
+the iron in the clay, which is converted into a red oxide, or rust, by
+water and heat.
+
+Common flower pots and the tiles used in draining wet land are not
+glazed, as hard-burned bricks are. The baking of these clay things is
+done with much less heat. They are left somewhat porous. But the tiles
+of roofs are baked harder, and get a surface glaze by the melting of the
+glassy particles of the sand.
+
+As bricks vary in colour and quality according to the materials that
+compose them, so the metamorphic rocks differ. The white sand one sees
+on many beaches is largely quartz. This is the substance of pure, white
+sandstone. Metamorphism melts the silica into a glassy liquid cement;
+the particles are bound close together on cooling. The rock becomes a
+white, granular quartzite, that looks like loaf sugar. If banded, it is
+called gneiss. Such rocks take a fine polish.
+
+Pure limestone is also white and granular. When metamorphosed by heat,
+it becomes white marble. The glassy cement that holds the particles of
+lime carbonate shows as the glaze of the polished surface. It is silica.
+One sees the same mineral on the face of polished granite.
+
+Clays are rarely pure. Kaolin is a white clay which, when baked, becomes
+porcelain. China-ware is artificially metamorphosed kaolin. In the
+early rocks the clay beds were transformed by heat into jasper and
+slates. In beds where clay mingled with sand, in layers, gneiss was
+formed. If mica is a prominent element, the metamorphic rock is easily
+parted into overlapping, scaly layers. It is a mica schist. If
+hornblende is the most abundant mineral, the same scaly structure shows
+in a dark rock called hornblende schist, rich in iron. A schist
+containing much magnesia is called serpentine.
+
+The bricks of the wall, the tiles on the roof, the flower pots on the
+window sill, and the dishes on the breakfast table, are examples of
+metamorphic rocks made by man's skill, by the use of fire and water
+acting on sand and clay. Pottery has preserved the record of
+civilization, from the making of the first crude utensils by cave men to
+the finest expression of decorative art in glass and porcelain.
+
+The choicest material of the builder and the sculptor is limestone baked
+by the fires under the earth's crust into marble. The most enduring of
+all the rocks are the foundation granite, and the metamorphic rocks that
+lie next to them. Over these lie thick layers of sedimentary rocks laid
+down by water. In them the record of life on the earth is written in
+fossils.
+
+
+
+
+THE AIR IN MOTION
+
+
+Most of the beautiful things that surround us and make our lives full of
+happiness appeal to one or more of our five senses. The green trees we
+can see, the bird songs we hear, the perfume of honey-laden flowers we
+smell, the velvety smoothness of a peach we feel, and its rich pulp we
+taste. But over all and through all the things we see and feel and hear
+and taste and smell, is the life-giving air, that lies like a blanket,
+miles in depth, upon the earth. The substance which makes the life of
+plants and animals possible is, when motionless, an invisible,
+tasteless, odourless substance, which makes no sound and is not
+perceptible to the touch.
+
+Air fills the porous substance of the earth's crust for a considerable
+distance, and even the water has so much air in it that fishes are able
+to breathe without coming to the surface. It is not a simple element,
+like gold, or carbon, or calcium, but is made up of several elements,
+chief among which are nitrogen and oxygen. Four-fifths of its bulk is
+nitrogen and one-fifth oxygen. There is present in air more or less of
+watery vapour and of carbon dioxide, the gas which results from the
+burning or decay of any substance. Although no more than one per cent.
+of the air that surrounds us is water, yet this is a most important
+element. It forms the clouds that bear water back from the ocean and
+scatter it in rain upon the thirsty land. Solid matter in the form of
+dust, and soot from chimneys, accumulates in the clouds and does a good
+work in condensing the moisture and causing it to fall.
+
+It is believed that the air reaches to a height of one hundred to two
+hundred miles above the earth's surface. If a globe six feet in diameter
+were furnished with an atmosphere proportionately as deep as ours, it
+would be about an inch in depth. At the level of the sea the air reaches
+its greatest density. Two miles above sea-level it is only two-thirds as
+dense. On the tops of high mountains, four or five miles above sea
+level, the air is so rarefied as to cause the blood to start from the
+nostrils and eyelids of explorers. The walls of the little blood-vessels
+are broken by the expansion of the air that is inside. At the sea-level
+air presses at the rate of fifteen pounds per square foot in all
+directions. As one ascends to higher levels, the air pressure becomes
+less and less.
+
+The barometer is the instrument by which the pressure of air is
+measured. A glass tube, closed at one end, and filled with mercury, the
+liquid metal often called quicksilver, is inverted in a cup of the same
+metal, and so supported that the metal is free to flow between the two
+vessels. The pressure of air on the surface of the mercury in the cup is
+sufficient at the sea-level to sustain a column of mercury thirty
+inches high in the tube. As the instrument is carried up the side of a
+mountain the mercury falls in the tube. This is because the air pressure
+decreases the higher up we go. If we should descend into the shaft of
+the deepest mine that reaches below the sea level, the column of air
+supported by the mercury in the cup would be a mile higher, and for this
+reason its weight would be correspondingly greater. The mercury would
+thus be forced higher in the tube than the thirty-inch mark, which
+indicates sea-level.
+
+Another form of barometer often seen is a tube, the lower and open end
+of which forms a U-shaped curve. In this open end the downward pressure
+of the air rests upon the mercury and holds it up in the closed end,
+forcing it higher as the instrument is carried to loftier altitudes. At
+sea level a change of 900 feet in altitude makes a change of an inch in
+the height of the mercury in the column. The glass tube is marked with
+the fractions of inches, or of the metre if the metric system of
+measurements is used.
+
+It is a peculiarity of air to become heated when it is compressed, and
+cooled when it is allowed to expand again. It is also true that when the
+sun rises, the atmosphere is warmed by its rays. This is why the hottest
+part of the day is near noon when the sun's rays fall vertically. The
+earth absorbs a great deal of the sun's heat in the daytime and through
+the summer season. When it cools this heat is given off, thus warming
+the surrounding atmosphere. In the polar regions, north and south, the
+air is far below freezing point the year round. In the region of the
+Equator it rarely falls below 90 degrees, a temperature which we find
+very uncomfortable, especially when there is a good deal of moisture in
+the air.
+
+If we climb a mountain in Mexico, we leave the sultry valley, where the
+heat is almost unbearable, and very soon notice a change. For every
+three hundred feet of altitude we gain there is a fall of one degree in
+the temperature. Before we are half way up the slope we have left behind
+the tropical vegetation, and come into a temperate zone, where the
+plants are entirely different from those in the lower valley. As we
+climb, the vegetation becomes stunted, and the thermometer drops still
+lower. At last we come to the region of perpetual snow, where the
+climate is like that of the frozen north.
+
+So we see that the air becomes gradually colder as we go north or south
+from the Equator, and the same change is met as we rise higher and
+higher from the level of the sea.
+
+It is only when air is in motion that we can feel and hear it, and there
+are very few moments of the day, and days of the year, when there is not
+a breeze. On a still day fanning sets the air in motion, and creates a
+miniature breeze, the sound of which we hear in the swishing of the fan.
+The great blanket of air that covers the earth is in a state of almost
+constant disturbance, because of the lightness of warm air and the
+heaviness of cold air. These two different bodies are constantly
+changing places. For instance, the heated air at the Equator is
+constantly being crowded upward by cold air which settles to the level
+of the earth. Cold streams of air flow to the Tropics from north and
+south of the Equator, and push upward the air heated by the sun.
+
+This constant inrush of air from north and south forms a double belt of
+constant winds. If the earth stood still, no doubt the direction would
+be due north and due south for these winds; but the earth rotates
+rapidly from west to east upon its axis, carrying with it everything
+that is securely fastened to the surface: the trees, the houses, etc.
+But the air is not a part of the earth, not even so much as the seas,
+the waters of which must stay in their proper basins, and be whirled
+around with other fixed objects. The earth whirls so rapidly that the
+winds from north and south of the Equator lag behind, and thus take a
+constantly diagonal direction. Instead of due south the northern belt of
+cold air drifts south-west and the southern belt drifts northwest. These
+are called the Trade Winds. Near the Equator they are practically east
+winds.
+
+The belt of trade winds is about fifty degrees wide. It swings northward
+in our summer and southward in our winter, its centre following the
+vertical position of the sun. Near the centre of the course which marks
+the meeting of the northern with the southern winds is a "Belt of
+Calms" where the air draws upward in a strong draught. The colder air of
+the trade winds is pushing up the columns of light, heated air. This
+strip is known by sailors as "the Doldrums," or "the region of
+equatorial calms." Though never wider than two or three hundred miles,
+this is a region dreaded by captains of sailing-vessels, for they often
+lie becalmed for weeks in an effort to reach the friendly trade winds
+that help them to their desired ports. Vessels becalmed are at the mercy
+of sudden tempests which come suddenly like thunder-storms, and
+sometimes do great damage to vessels because they take the sailors
+unawares and allow no time to shorten sail.
+
+Until late years the routes of vessels were charted so that sailors
+could take advantage of the trade winds in their long voyages. It was
+necessary in the days of sailing-vessels for the captain to understand
+the movements of winds which furnished the motive power that carried his
+vessel. Fortunate it was for him that there were steady winds in the
+temperate zones that he could take advantage of in latitudes north of
+the Tropic of Cancer and south of the Tropic of Capricorn. What becomes
+of the hot air that rises in a constant stream above the "Doldrums,"
+pushed up by the cooler trade winds that blow in from north and south?
+Naturally this air cannot ascend very high, for it soon reaches an
+altitude in which its heat is rapidly lost, and it would sink if it
+were not constantly being pushed by the rising column of warm air under
+it. So it turns and flows north and south at a level above the trade
+winds. Not far north of the Tropic of Cancer it sinks to the level of
+sea and land, and forms a belt of winds that blows ships in a
+northeasterly direction. Between trades and anti-trades is another zone
+of calms,--near the Tropics of Cancer and of Capricorn.
+
+The land masses of the continents with their high mountain ranges
+interfere with these winds, especially in the northern hemisphere, but
+in the Southern Pacific and on the opposite side of the globe the
+"Roaring Forties," as these prevailing westerly winds are known by the
+sailors, have an almost unbroken waste of seas over which they blow. In
+the long voyages between England and Australia, and in the Indian trade,
+the ships of England set their sails to catch the roaring forties both
+going and coming. They accomplish this by sailing past the Cape of Good
+Hope on the outward voyage and coming home by way of Cape Horn, thus
+circling the globe with every trip. In the North Atlantic, traffic is
+now mostly carried on in vessels driven by engines, not by sails. Yet
+the westerly winds that blow from the West Indies diagonally across the
+Atlantic are still useful to all sailing craft that are making for
+British ports.
+
+From the north and from the south cold air flows down into the regions
+of warmer climate. These polar winds are not so important to sea
+commerce, but they do a great work in tempering the heat in the
+equatorial regions. We cannot know how much our summers are tempered by
+the cool breath of winds that blow over polar ice-fields. And the cold
+regions of the earth, in their brief summer, enjoy the benefits of the
+warm breezes that flow north and south from the heated equatorial
+regions.
+
+The land, north and south, is made habitable by the clouds. They gather
+their burdens of vapour from the warm seas, the wind drifts them north
+and south, where they let it fall in rains that make and keep the earth
+green and beautiful. From the clouds the earth gathers, like a great
+sponge, the water that stores the springs and feeds rivers and lakes.
+How necessary are the winds that transport the cloud masses!
+
+The air is the breath of life to all living things on our planet. Mars
+is one of the sun's family so provided. Plants or animals could probably
+live on the planet Mars. Do we think often enough of this invisible,
+life-giving element upon which we depend so constantly?
+
+The open air which the wind purifies by keeping it in motion is the best
+place in which to work, to play, and to sleep, when work and play are
+done and we rest until another day comes. Indoors we need all the air we
+can coax to come in through windows and doors. Fresh air purifies air
+that is stale and unwholesome from being shut up. Nobody is afraid,
+nowadays, to breathe night air! What a foolish notion it was that led
+people to close their bedroom windows at night. Clean air, in plenty,
+day and night, we need. Air and sunshine are the two best gifts of God.
+
+
+
+
+THE WORK OF THE WIND
+
+
+When the March wind comes blustering down the street, rudely dashing a
+cloud of dust in our faces, we are uncomfortable and out of patience. We
+duck our heads and cover our faces, but even then we are likely to get a
+cinder in one eye, to swallow germs by the dozens, and to get a gray
+coating of plain, harmless dust. We welcome the rain that lays the dust,
+or its feeble imitation, the water sprinkler, that brings us temporary
+relief.
+
+On the quietest day, even after a thorough sweeping and dusting of the
+library, you are able to write your name plainly on the film of dust
+that lies on the polished table. Take a book from the open shelves, and
+blow into the trough of its top. This is always dusty. Where does the
+dust come from? This is the house-keeper's riddle.
+
+The answer is not a hard one. I look out of my window on a street which
+is famous as the road Washington took on his retreat from White Plains
+to Trenton. It has always been the main thoroughfare between New York
+and Philadelphia, and now is the route that automobiles follow. A
+constant procession of vehicles passes my house, and to-day each one
+approaches in a cloud of dust. The air is gray with suspended particles
+of dirt. The wind carries the successive clouds, and they roll up
+against the houses like breakers on the beach. Windows and doors are
+loose enough to let dust sift in. When a door opens, the cloud enters
+and lights on rugs and carpets and curtains. Any ledge collects its
+share of dust. The beating of carpets and rugs disturbs the accumulated
+dust of many months.
+
+[Illustration: In this lonely Arizona desert the wind drifts the sand
+into dunes, just as it does on the toe of Cape Cod]
+
+[Illustration: The Grand Canyon of the Colorado shows on a magnificent
+scale the work of water in cutting away rock walls]
+
+The wind sweeps the ploughed field, and takes all the dust it can carry.
+It blows the finest top soil from our gardens into the street. It blows
+soil from other fields and gardens into ours, so the level of our land
+is not noticeably lowered. The wind strips the high land and drops its
+burden on lower levels. This is one of the big jobs the water has to do,
+and the wind is a valuable helper. To tear down the mountains and fill
+in the valleys is the great work of the two partners, wind and water.
+
+Dead, still air holds the finest dust, without letting it fall. The
+buoyancy of the particles overcomes their weight. We see them in a
+sunbeam, like shining points of precious metal, and watch them. A light
+breeze picks up bits of soil and litter, from the smallest up to a
+certain size and weight. If the velocity of the wind increases, its
+carrying power increases. It is able to carry bits that are larger and
+heavier. The following table is exact and interesting:
+
+                      _Velocity_      _Pressure_
+                      _in Miles_      _in Pounds_
+                      _per Hour_     _per Sq. Ft._
+
+  Light breeze              14                   1
+  Strong breeze             42                   9
+  Strong gale               70                  25
+  Hurricane                 84                  36
+
+The terrible paths of hurricanes are seen in forest countries. The trees
+are uprooted, as if a great roller had crushed them, throwing the tops
+all in one direction, and leaving the roots uncovered, and a sunken
+pocket where each tree stood. On a steep, rocky slope, the uprooting of
+scattered trees often loosens tons of rock, and sends the mass
+thundering down the mountain-side. Much more destruction may be
+accomplished by one brief tornado than by years of wear by ordinary
+breezes.
+
+The wind does much to help the waves in their patient beating on rocky
+shores. If the wind blows from the ocean and the tide is landward, the
+two forces combine, and the loose rocks are thrown against the solid
+beach with astonishing force. Even the gravel and the sharp sand are
+tools of great usefulness to the waves in grinding down the resisting
+shore. Up and back they are swept by the water, and going and coming
+they have their chance to scratch or strike a blow. Boulders on the
+beach become pockmarked by the constant sand-blast that plays upon them.
+The lower windows of exposed seaside houses are dimmed by the sand that
+picks away the smooth surface outside, making it ground glass by the
+same process used in the factory. Lighthouses have this difficulty in
+keeping their windows clear. The "lantern" itself is sometimes reached
+by the sand grains. That is the cupola in which burns the great light
+that warns vessels away from the rocks and tells the captain where he
+is.
+
+In the Far Western States the telegraph poles and fence posts are soon
+cut off at the ground by the flinty knives the wind carries. These are
+the grains of sand that are blown along just above the ground. The trees
+are killed by having their bark girdled in this way. The sand-storms
+which in the orange and lemon region of California are called "Santa
+Anas" sometimes last two or three days, and damage the trees by piercing
+the tender bark with the needle-pointed sand.
+
+Wind-driven soil, gathered from the sides of bare hills and mountains,
+fills many valleys of China with a fine, hard-packed material called
+"loess." In some places it is hundreds of feet deep. The people dig into
+the side of a hill of this loess and carry out the diggings, making
+themselves homes, of many rooms, with windows, doors, and solid walls
+and floors, all in one solid piece, like the chambered house a mole
+makes underground in the middle of a field. So compact is the loess that
+there is no danger of a cave-in.
+
+The hills of sand piled up on the southern shore of Lake Michigan, and
+at Provincetown, at the toe of Cape Cod, are the work of the wind. On
+almost any sandy shore these "dunes" are common. The long slope is
+toward the beach that furnishes the sand. The wind does the building. Up
+the slope it climbs, then drops its burden, which slides to the bottom
+of an abrupt landward steep. There is a gradual movement inland if the
+strongest winds come from the water. The shifting of the dunes threatens
+to cover fertile land near them. In the desert regions, the border-land
+is always in danger of being taken back again, even though it has been
+reclaimed from the desert and cultivated for long years.
+
+Besides tearing down, carrying away, and building up again the fragments
+of the earth's crust, the wind does much that makes the earth a pleasant
+planet to live on. It drives the clouds over the land, bringing rains
+and snows and scattering them where they will bless the thirsty ground
+and feed the springs and brooks and rivers. It scatters the seeds of
+plants, and thus plants forests and prairies and lovely mountain slopes,
+making the wonderful wild gardens that men find when they first enter
+and explore a new region. The trade winds blow the warm air of the
+Tropics north and south, making the climate of the northern countries
+milder than it would otherwise be. Sea winds blow coolness over the land
+in summer, and cool lake breezes temper the inland regions. From the
+snow-capped mountains come the winds that refresh the hot, tired worker
+in the valleys.
+
+Everywhere the wind blows, the life-giving oxygen is carried. This is
+what we mean when we speak of fresh air. Stagnant air is as unwholesome
+as stagnant water. Constant moving purifies both. So we must give the
+wind credit for some of the greatest blessings that come into our lives.
+Light and warmth come from the sun. Pure water and pure air are gifts
+the bountiful earth provides. Without them there would be no life on the
+earth.
+
+
+
+
+RAIN IN SUMMER
+
+
+    How beautiful is the rain!
+    After the dust and heat,
+    In the broad and fiery street,
+    In the narrow lane,
+    How beautiful is the rain!
+
+    How it clatters along roofs,
+    Like the tramp of hoofs!
+    How it gushes and struggles out
+    From the throat of the overflowing spout!
+    Across the window-pane
+
+    It pours and pours;
+    And swift and wide,
+    With a muddy tide,
+    Like a river down the gutter roars
+    The rain, the welcome rain!
+
+    The sick man from his chamber looks
+    At the twisted brooks;
+    He can feel the cool
+    Breath of each little pool;
+    His fevered brain
+    Grows calm again,
+    And he breathes a blessing on the rain.
+
+                 --HENRY W. LONGFELLOW.
+
+
+
+
+WHAT BECOMES OF THE RAIN?
+
+
+The clouds that sail overhead are made of watery vapour. Sometimes they
+look like great masses of cotton-wool against the intense blue of the
+sky. Sometimes they are set like fleecy plumes high above the earth.
+Sometimes they hang like a sullen blanket of gray smoke, so low they
+almost touch the roofs of the houses. Indeed, they often rest on the
+ground and then we walk through a dense fog.
+
+In their various forms, clouds are like wet sponges, and when they are
+wrung dry they disappear--all their moisture falls upon the earth. When
+the air is warm, the water comes in the form of rain. If it is cold, the
+drops are frozen into hail, sleet, or snow.
+
+All of the water in the oceans, in the lakes and rivers, great and
+small, all over the earth, comes from one source, the clouds. In the
+course of a year enough rain and snow fall to cover the entire surface
+of the globe to a depth of forty inches. This quantity of water amounts
+to 34,480 barrels on every acre. What becomes of it all?
+
+We can easily understand that all the seas and the other bodies of water
+would simply add forty inches to their depth, and many would become
+larger, because the water would creep up on their gradually sloping
+shores. We have to account for the rain and the snow that fall upon the
+dry land and disappear.
+
+Go out after a drenching rainstorm and look for the answer to this
+question. The gullies along the street are full of muddy, running water.
+There are pools of standing water on level places, but on every slope
+the water is hurrying away. The ground is so sticky that wagons on
+country roads may mire to the hubs in the pasty earth. There is no use
+in trying to work in the garden or to mow the lawn. The sod is soft as a
+cushion, and the garden soil is water-soaked below the depth of a
+spading-fork.
+
+The sun comes out, warm and bright, and the flagstones of the sidewalk
+soon begin to steam like the wooden planks of the board walk. The sun is
+changing the surface water into steam which rises into the sky to form a
+part of another bank of clouds. The earth has soaked up quantities of
+the water that fell. If we followed the racing currents in the gullies
+we should find them pouring into sewer mains at various points, and from
+these underground pipes the water is conducted to some outlet like a
+river. All of the streams are swollen by the hundreds of brooks and
+rivulets that are carrying the surface water to the lowest level.
+
+[Illustration: Rain and wind are the sculptors that have carved these
+strange castles out of a rocky table]
+
+[Illustration: All the water in the seas, lakes, rivers, and springs
+came out of the clouds]
+
+So we can see some of the rainfall going back to the sky, some running
+off through rivulets to the sea, and some soaking into the ground. It
+will be interesting to follow this last portion as it gradually settles
+into the earth. The soil will hold a certain quantity, for it is made up
+of fine particles, all separated by air spaces, and it acts like a
+sponge. In seasons of drought and great heat the sun will draw this soil
+water back to the surface, by forming cracks in the earth, and fine,
+hair-like tubes, through which the vapour may easily rise. The gardener
+has to rake the surface of the beds frequently to stop up these channels
+by which the sun is stealing the precious moisture.
+
+The water that the surface soil cannot absorb sinks lower and lower into
+the ground. It finds no trouble to settle through layers of sand, for
+the particles do not fit closely together. It may come to a bed of clay
+which is far closer. Here progress is retarded. The water may
+accumulate, but finally it will get through, if the clay is not too
+closely packed. Again it may sink rapidly through thick beds of gravel
+or sand. Reaching another bed of clay which is stiffer by reason of the
+weight of the earth above it, the water may find that it cannot soak
+through. The only way to pass this clay barrier is to fill the basin,
+and to trickle over the edge, unless a place is found in the bottom
+where some looser substance offers a passage. Let us suppose that a
+concave clay basin of considerable depth is filled with water-soaked
+sand. At the very lowest point on the edge of this basin a stream will
+slowly trickle out, and will continue to flow, as long as water from
+above keeps the bowl full.
+
+It is not uncommon to find on hillsides, in many regions, little brooks
+whose beginnings are traceable to springs that gush out of the ground.
+The spring fills a little basin, the overflow of which is the brook. If
+the source of this spring could be traced underground, we might easily
+follow it along some loose rock formation until we come to a clay basin
+like the one described above. We might have to go down quite a distance
+and then up again to reach the level of this supply, but the level of
+the water at the mouth of the spring can never be higher than the level
+of the water in the underground supply basin.
+
+Often in hot summers springs "go dry." The level of water in the supply
+basin has fallen below the level of the spring. We must wait until
+rainfall has added to the depth of water in the basin before we can
+expect any flow into the pool which marks the place where the brook
+begins.
+
+Suppose we had no beds of clay, but only sand and gravel under the
+surface soil. We should then expect the water to sink through this loose
+material without hindrance, and, finding its way out of the ground, to
+flow directly into the various branches of the main river system of our
+region. After a long rain we should have the streams flooded for a few
+days, then dry weather and the streams all low, many of them entirely
+dry until the next rainstorm.
+
+Instead of this, the soil to a great depth is stored with water which
+cannot get away, except by the slow process by which the springs draw
+it off. This explains the steady flow of rivers. What should we do for
+wells if it were not for the water basins that lie below the surface? A
+shallow well may go dry. Its owner digs deeper, and strikes a lower
+"vein" of water that gives a more generous supply. In the regions of the
+country where the drift soil, left by the great ice-sheet, lies deepest,
+the glacial boulder clay is very far down. The surface water, settling
+from one level to another, finally reaches the bottom of the drift.
+Wells have to be deep that reach this water bed.
+
+The water follows the slope of this bed and is drained into the ocean,
+sometimes by subterranean channels, because the bed of the nearest river
+is on a much higher level. So we must not think that the springs contain
+only the water that feeds the rivers. They contain more.
+
+The layers of clay at different levels, from the surface down to the
+bottom of the drift, form water basins and make it possible for people
+to obtain a water supply without the expense of digging deep wells. The
+clayey subsoil, only a few feet below the surface, checks the downward
+course of the water, so that the sun can gradually draw it back, and
+keep a supply where plant roots can get it. The vapour rising keeps the
+air humid, and furnishes the dew that keeps all plant life comfortable
+and happy even through the hot summer months.
+
+Under the drift lie layers of stratified rock, and under these are the
+granites and other fire-formed rocks, the beginning of those rock masses
+which form the solid bulk of the globe. We know little about the core of
+the earth, but the granites that are exposed in mountain ridges are
+found to have a great capacity for absorbing water, so it is not
+unlikely that much surface water soaks into the rock foundations and is
+never drained away into the sea.
+
+The water in our wells is often hard. It becomes so by passing through
+strata of soil and rock made, in part, at least, of limestone, which is
+readily dissolved by water which contains some acid. Soil water absorbs
+acids from the decaying vegetation,--the dead leaves and roots of
+plants. Rain water is soft, and so is the water in ponds that have muddy
+basins, destitute of lime. Water in the springs and wells of the
+Mid-Western States is "hard" because it percolates through limestone
+material. In many parts of this country the well water is "soft,"
+because of the scarcity of limestone in the soil.
+
+I have seen springs around which the plants and the pebbles were coated
+with an incrustation of lime. "Petrified moss" is the name given to the
+plants thus turned to stone. The reason for this deposit is clear.
+Underground water is often subjected to great pressure, and at this time
+it is able to dissolve much more of any mineral substance than under
+ordinary conditions. When the pressure is released, the water is unable
+to hold in solution the quantity of mineral it contains; therefore, as
+it flows out through the mouth of the spring, the burden of mineral is
+laid down. The plants coated with the lime gradually decay, but their
+forms are preserved.
+
+There are springs the water of which comes out burdened with iron, which
+is deposited as a yellowish or red mineral on objects over which it
+flows. Ponds fed by these springs accumulate deposits of the mineral in
+the muddy bottoms. Some of the most valuable deposits of iron ore have
+accumulated in bogs fed by iron-impregnated spring water. In a similar
+way lime deposits called marl or chalk are made.
+
+
+
+
+THE SOIL IN FIELDS AND GARDENS
+
+
+City and country teachers are expected to teach classes about the
+formation and cultivation of soil. It is surprising how much of the
+needed materials can be brought in by the children, even in the cities.
+The beginning is a flowering plant growing in a pot. A window box is a
+small garden. A garden plot is a miniature farm.
+
+_Materials to collect for study indoors._ A few pieces of different
+kinds of rock: Granite, sandstone, slate; gravelly fragments of each,
+and finer sand. Pebbles from brooks and seashore. Samples of clays of
+different colors, and sands. Samples of sandy and clay soils, black pond
+muck, peat and coal. Rock fossils. A box of moist earth with earthworms
+in it. _Keep it moist._ A piece of sod, and a red clover plant with the
+soil clinging to its roots.
+
+_What is soil?_ It is the surface layer of the earth's crust, sometimes
+too shallow on the rocks to plough, sometimes much deeper. Under deep
+soil lies the "subsoil," usually hard and rarely ploughed.
+
+_What is soil made of?_ Ground rock materials and decayed remains of
+animal and plant life. By slow decay the soil becomes rich food for the
+growing of new plants. Wild land grows up to weeds and finally to
+forests. The soil in fields and gardens is cultivated to make it
+fertile. Plants take fertility from the soil. To maintain the same
+richness, plant food must be put back into the soil. This is done by
+deep tillage, and by mixing in with the soil manures, green crops, like
+clover, and commercial fertilizers.
+
+_Plants must be made comfortable, and must be fed._ Few plants are
+comfortable in sand. It gets hot, it lets water through, and it shifts
+in wind and is a poor anchor for roots. Clay is so stiff that water
+cannot easily permeate it; roots have the same trouble to penetrate it
+and get at the food it is rich in. Air cannot get in.
+
+Sand mixed with clay makes a mellow soil, which lets water and air pass
+freely through. The roots are more comfortable, and the tiny root hairs
+can reach the particles of both kinds of mineral food. But the needful
+third element is decaying plant and animal substances, called "humus."
+These enrich the soil, but they do a more important thing: their decay
+hastens the release of plant food from the earthy part of the soil, and
+they add to it a sticky element which has a wonderful power to attract
+and hold the water that soaks into the earth.
+
+_What is the best garden soil?_ A mixture of sand, clay, and humus is
+called "loam." If sand predominates, it is a sandy loam--warm, mellow
+soil. If clay predominates, we have a clay loam--a heavy, rich, but
+cool soil. All gradations between the two extremes are suited to the
+needs of crops, from the melons on sandy soil, to celery that prefers
+deep, cool soil, and cranberries that demand muck--just old humus.
+
+_How do plant roots feed in soil?_ By means of delicate root hairs which
+come into contact with particles of soil around which a film of soil
+water clings. This fluid dissolves the food, and the root absorbs the
+fluid. Plants can take no food in solid form. Hence it is of the
+greatest importance to have the soil pulverized and spongy, able to
+absorb and hold the greatest amount of water. The moisture-coated soil
+particles must have air-spaces between them. Air is as necessary to the
+roots as to the tops of growing plants.
+
+_Why does the farmer plough and harrow and roll the land?_ To pulverize
+the soil; to mellow and lighten it; to mix in thoroughly the manure he
+has spread on it, and to reach, if he can, the deeper layers that have
+plant food which the roots of his crops have not yet touched. Killing
+weeds is but a minor business, compared with tillage.
+
+Later, ploughing or cultivating the surface lightly not only destroys
+the weeds, but it checks the loss of water by evaporation from the
+cracks that form in dry weather. Raking the garden once a day in dry
+weather does more good than watering it. The "dust mulch" acts as a cool
+sunguard over the roots.
+
+_The process of soil-making._ If the man chopping wood in the Yosemite
+Valley looks about him he can see the soil-making forces at work on a
+grand scale. The bald, steep front of El Capitan is of the hardest
+granite, but it is slowly crumbling, and its fragments are accumulating
+at the bottom of the long slope. Rain and snow fill all crevices in the
+rocks. Frost is a wonderful force in widening these cracks, for water
+expands when it freezes. The loosened rock masses plough their way down
+the steep, gathering, as they go, increasing power to tear away any
+rocks in their path.
+
+Wind blows finer rock fragments along, and they lodge in cracks. Fine
+dust and the seeds of plants are lodged there. The rocky slopes of the
+Yosemite Valley are all more or less covered with trees and shrubs that
+have come from wind-sown seeds. These plants thrust their roots deeper
+each year into the rock crevices. The feeding tips of roots secrete
+acids that eat away lime and other substances that occur in rocks. Dead
+leaves and other discarded portions of the trees rot about their roots,
+and form soil of increasing depth. The largest trees grow on the rocky
+soil deposited at the base of the slope. The tree's roots prevent the
+river from carrying it off.
+
+When granite crumbles, its different mineral elements are separated.
+Clear, glassy particles of quartz we call sand. Dark particles of
+feldspar become clay, and may harden into slate. Sand may become
+sandstone. Exposed slate and sandstone are crumbled by exposure to wind
+and frost and moving water, and are deposited again as sand-bars and
+beds of clay.
+
+The most interesting phase of soil study is the discovery of what a work
+the humble earthworm does in mellowing and enriching the soil.
+
+
+
+
+THE WORK OF EARTHWORMS
+
+
+The farmer and the gardener should expect very poor crops if they
+planted seed without first ploughing or spading the soil. Next, its fine
+particles must be separated by the breaking of the hard clods. A wise
+man ploughs heavy soil in the fall. It is caked into great clods which
+crumble before planting time. The water in the clods freezes in winter.
+The expansion due to freezing makes this soil water a force that
+separates the fine particles. So the frost works for the farmer.
+
+Just under the surface of the soil lives a host of workers which are our
+patient friends. They work for their living, and are perhaps unconscious
+of the fact that they are constantly increasing the fertility of the
+soil. They are the earthworms, also called fishworms, which are
+distributed all over the world. They are not generally known to farmers
+and gardeners as friendly, useful creatures, and their services are
+rarely noticed. We see robins pulling them out of the ground, and we are
+likely to think the birds are ridding us of a garden pest. What we need
+is to use our eyes, and to read the wonderful discoveries recorded in a
+book called "Vegetable Mould and Earthworms," written by Charles
+Darwin.
+
+The benefits of ploughing and spading are the loosening and pulverizing
+of the packed earth; the mixing of dead leaves and other vegetation on
+and near the surface with the more solid earth farther down; the letting
+in of water and air; and the checking of loss of water through cracks
+the sun forms by baking the soil dry.
+
+The earthworm is a creature of the dark. It cannot see, but it is
+sufficiently sensitive to light to avoid the sun, the rays of which
+would shrivel up its moist skin. Having no lungs or gills, the worm uses
+the skin as the breathing organ; and it must be kept moist in order to
+serve its important use. This is why earthworms are never seen above
+ground except on rainy days, and never in the top soil if it has become
+dry. In seasons of little rain, they go down where the earth is moist,
+and venture to the surface only at night, when dew makes their coming up
+possible.
+
+Earthworms have no teeth, but they have a long snout that protrudes
+beyond the mouth. Their food is found on and in the surface soil. They
+will eat scraps of meat by sucking the juices, and scrape off the pulp
+of leaves and root vegetables in much the same way. Much of their
+subsistence is upon organic matter that can be extracted from the soil.
+Quantities of earth are swallowed. It is rare that an earthworm is dug
+up that does not show earth pellets somewhere on their way through the
+long digestive canal. The rich juices of plant substance are absorbed
+from these pellets as they pass through the body.
+
+Earthworms explore the surface of the soil by night, and pick up what
+they can find of fresh food. Nowhere have I heard of them as a nuisance
+in gardens, but they eagerly feed on bits of meat, especially fat, and
+on fresh leaves. They drag all such victuals into their burrows, and
+begin the digestion of the food by pouring on it from their mouths a
+secretion somewhat like pancreatic juice.
+
+The worms honeycomb the earth with their burrows, which are long,
+winding tubes. In dry or cold weather these burrows may reach eight feet
+under ground. They run obliquely, as a rule, from the surface, and are
+lined with a layer of the smooth soil, like soft paste, cast from the
+body. The lining being spread, the burrow fits the worm's body closely.
+This enables it to pass quickly from one end to the other, though it
+must wriggle backward or forward without turning around.
+
+At the lower end of the burrow, an enlarged chamber is found, where
+hibernating worms coil and sleep together in winter. At the top, a
+lining of dead leaves extends downward for a few inches, and in day time
+a plug of the same material is the outside door. At night the worm comes
+to the surface, and casts out the pellets of earth swallowed. The burrow
+grows in length by the amount of earth scraped off by the long snout
+and swallowed. The daily amount of excavation done is fairly estimated
+by the castings observed each morning on the surface.
+
+One earthworm's work for the farmer is not very much, but consider how
+many are at work, and what each one is doing. It is boring holes through
+the solid earth, and letting in the surface water and the air. It is
+carrying the lower soil up to the surface, often the stubborn subsoil,
+that no plough could reach. It is burying and thus hastening the decay
+of plant fibre, which lightens heavy soil and makes it rich because it
+is porous. Moreover, the earthworms are doing over and over again this
+work of fining and turning over the soil, which the plough does but
+seldom.
+
+By the continuous carrying up of their castings, the earthworms
+gradually bury manures spread on the surface. The collapse of their
+burrows and the making of new ones keep the soil constantly in motion.
+The particles are being loosened and brought into contact with the soil
+water, that dissolves, and thus frees for the use of feeding roots, the
+plant food stored in the rock particles that compose the mineral part of
+the soil.
+
+The weight of earth brought to the surface by worms in the course of a
+year has been carefully estimated. Darwin gives seven to eighteen tons
+per acre as the lowest and highest reports, based on careful collecting
+of castings by four observers, working on small areas of totally
+different soils. In England, earthworms have done a great deal more
+toward burying boulders and ancient ruins than any other agency. They
+eagerly burrow under heavy objects, the weight of which causes them to
+crush the honeycombed earth. Undiscouraged, the earthworms repeat their
+work.
+
+"Long before man existed, the land was regularly ploughed, and continues
+still to be ploughed by earthworms. It may be doubted whether there are
+many other animals which have played so important a part in the history
+of the world as have these lowly organized creatures."
+
+After years of study, Charles Darwin came to this conclusion. The more
+we study the lives of these earth-consuming creatures, the more fully do
+we believe what the great nature student said. The fertile soil is made
+of rock meal and decayed leaves and roots. Only recently have ploughs
+been invented. But the great forest crops have grown in soil made mellow
+by the earthworm's ploughing.
+
+
+
+
+QUIET FORCES THAT DESTROY ROCKS
+
+
+Wind and water are the blustering active agents we see at work tearing
+down rocks and carrying away their particles. They do the most of this
+work of levelling the land; but there are quiet forces at work which
+might not attract our attention at all, and yet, without their help,
+wind and running water would not accomplish half the work for which they
+take the credit.
+
+The air contains certain destructive gases which by their chemical
+action separate the particles of the hardest rocks, causing them to
+crumble. Now the wind blows away these crumbling particles, and the
+solid unchanged rock beneath is again exposed to the crumbling agencies.
+
+The changes in temperature between day and night cause rocks to contract
+and expand, and these changes put a strain upon the mineral particles
+that compose them. Much scaling of rock surfaces is due to these causes.
+Building a fire on top of a rock, and then dashing water upon the heated
+mass, shatters it in many directions. This process merely intensifies
+the effect produced by the mild changes of winter and summer. Water is
+present in most rocks, in surprising quantities, often filling the
+spaces in porous rocks like sandstones.
+
+When winter brings the temperature down to the freezing point, the water
+near the surface of the rock first feels it. Ice forms, and every
+particle of water is swollen by the change. A strain is put upon the
+mineral particles against which the particles of ice crowd for more
+room. Frost is a very powerful agent in the crumbling of rocks, as well
+as of stubborn clods of earth. In warm climates, and in desert regions
+where there is little moisture in the rocks, this destructive action of
+freezing water is not known. In cold countries, and in high altitudes,
+where the air is heavy with moisture, its greatest work is done.
+
+Some kinds of rock decay when they become dry, and resist crumbling
+better when they absorb a certain amount of moisture. Alternate wetting
+and drying is destructive to certain rocks.
+
+One of the unnoticed agents of rock decay is the action of lowly plants.
+Mosses grow upon the faces of rocks, thrusting their tiny root processes
+into pits they dig deeper by means of acids secreted by the delicate
+tips. You have seen shaded green patches of lichens, like little rugs,
+of different shapes, spread on the surface of rocks. But you cannot see
+so well the work these growths are doing in etching away the surface,
+and feeding upon the decaying mineral substance.
+
+Mosses and lichens do a mighty work, with the help of water, in
+reducing rocks to their original elements, and thus forming soil. No
+plants but lichens and mosses can grow on the bare faces of rocks. As
+their root-like processes lengthen and go deeper into the rock face,
+particles are pried off, and the under-substance is attacked. Higher
+plants then find a footing. Have you not seen little trees growing on a
+patch of moss which gets its food from the air and the rock to which it
+clings? The spongy moss cushion soaks up the rain and holds it against
+the rock face. A streak of iron in the rock may cause the water to
+follow and rust it out, leaving a distinct crevice. Now the roots of any
+plant that happens to be growing on the moss may find a foot-hold in the
+crack. Streaks of lime in a rock readily absorb water, which gradually
+dissolves and absorbs its particles, inviting the roots to enter these
+new passages and feed upon the disintegrating minerals. Dead leaves
+decay, and the acids the trickling water absorbs from them are
+especially active in disintegrating lime rocks.
+
+From such small beginnings has resulted the shattering of great rock
+masses by the growth of plants upon them. Tree roots that grow in rock
+crevices exert a power that is irresistible. The roots of smaller plants
+do the same great work in a quieter way.
+
+When a hurricane or a flood tears down the mountain-side, sweeping
+everything before it, trees, torn out by the roots, drag great masses
+of rock and soil into the air, and fling them down the slope. Wind and
+water thus finish the destruction which the humble mosses and lichens
+began. What seemed an impregnable fortress of granite has crumbled into
+fragments. Its particles are reduced to dust, or are on the way to this
+condition. The plant food locked up in granite boulders becomes
+available to hungry roots. Forests, grain-fields, and meadows cover the
+work of destructive agencies with a mantle of green.
+
+
+
+
+HOW ROCKS ARE MADE
+
+
+The granite shaft is made out of the original substance of the earth's
+crust. Its minerals are the elements out of which all of the rock masses
+of the earth are formed, no matter how different they look from granite.
+Sandstone is made of particles of quartz. Clay and slate are made out of
+feldspar and mica. Iron ore comes from the hornblende in granite. The
+mineral particles, reassembled in different proportions, form all of the
+different rocks that are known.
+
+Here in my hand is a piece of pudding-stone. It is made of pebbles of
+different sizes, each made of different coloured minerals. The pebbles
+are cemented together with a paste that has hardened into stone. This
+kind of rock the geologists call _conglomerate_. Pudding-stone is the
+common name, for the pebbles in the pasty matrix certainly do suggest
+the currants and the raisins that are sprinkled through a Christmas
+pudding.
+
+Under the seashores there are forming to-day thick beds of sand. The
+rivers bring the rock material down from the hills, and it is sorted and
+laid down. The moving water drops the heaviest particles near shore, and
+carries the finer ones farther out before letting them fall.
+
+[Illustration: The town of Cripple Creek, Colorado, which has grown up
+like magic since 1891, covers the richest gold and silver mines in the
+world]
+
+[Illustration: The level valley is filled up with fine rock flour washed
+from the sides of the neighboring mountains]
+
+The hard water, that comes through limestone rocks, adds lime in
+solution to the ocean water. All the shellfish of the sea, and the
+creatures with bony skeletons, take in the bone-building, shell-making
+lime with their food. Generations of these inhabitants of the sea have
+died, and their shells and bones have accumulated and been transformed
+into thick beds of limestone on the ocean floor. This is going on
+to-day; but the limestone does not accumulate as rapidly as when the
+ocean teemed with shell-bearing creatures of gigantic size. Of these we
+shall speak in another chapter.
+
+The fine dust that is blown into the ocean from the land, and that makes
+river water muddy, accumulates on the sea bottom as banks of mud, which
+by the burden of later deposits is converted into clay. Sandstone is but
+the compressed sand-bank.
+
+In the study of mountains, geologists have discovered that old seashores
+were thrown up into the first great ridges that form the backbone of a
+mountain system. The Rocky Mountains, and the Appalachian system on the
+east, were made out of thick strata of rocks that had been formed by
+accumulations of mud and sand--the washings of the land--on the opposite
+shores of a great mid-continental sea, that stretched from the crest of
+one great mountain system across to the other, and north and south from
+the Laurentian Hills to the Gulf of Mexico. The great weight of the
+accumulating layers of rock materials on one side, and the wasted land
+surfaces on the other, made the sea border a line of greatest weakness
+in the crust of the earth. The shrinking of the globe underneath caused
+the break; mashing and folding followed, throwing the ridge above
+sea-level, and making dry land out of rock waste which had been
+accumulating, perhaps for millions of years, under the sea. The
+wrinkling of the earth's crust was the result of crushing forces which
+produced tremendous heat.
+
+Streams of lava sprang out through the fissures and poured streams of
+melted rock down the sides of the fold, quite burying, in many places,
+the layers of limestone, sandstone, and clay. Between the strata of
+water-formed rocks there were often created chimney-like openings, into
+which molten rock from below was forced, forming, when cool, veins and
+dikes of rock material, specimens of the substance of the earth's
+interior.
+
+Tremendous pressure and heat, acting upon stratified rocks saturated
+with water transform them into very different kinds of rock. Limestone,
+subjected to these forces, is changed into marble. Clays are transformed
+into slates. Sandstone is changed into quartzite, the sand grains being
+melted so as to become no longer visible to the naked eye. The
+anthracite coal of the Pennsylvania mountains is the result of heat and
+pressure acting upon soft coal. Associated with these beds of hard coal
+are beds of black lead, or graphite, the substance used in making "lead"
+pencils. We believe that the same forces that operated to transform clay
+rocks into slate, and limestone into marble, transformed soft coal into
+hard, and hard coal into graphite, in the days when the earth was young.
+
+The word _sedimentary_ is applied to rocks which were originally laid
+down under water, as sediment, brought by running water, or by wind, or
+by the decay of organic substances. _Stratified_ rocks are those which
+are arranged in layers. Sedimentary rocks will fall into this class.
+_Aqueous_ rocks are those which are formed under water. Most of the
+stratified and sedimentary rocks, but not all, may be included under
+this term. Rocks that are made out of fragments of other rocks torn down
+by the agencies of erosion are called _fragmental_. Wind, water, and ice
+are the three great agencies that wear away the land, bring rock
+fragments long distances, and deposit them where aqueous rocks are being
+formed. Volcanic eruptions bring material from the earth's interior.
+This material ranges all the way from huge boulders to the finest
+impalpable dust, called volcanic ashes. Rivers of ice called glaciers
+crowd against their banks, loosening rock masses and carrying away
+fragments of all sizes, in their progress down the valley. Brooks and
+rivers carry the pebbles and the larger rock masses they are able to
+loosen from their walls and beds, and grind them smooth as they move
+along toward lower levels.
+
+The air itself causes rocks to crumble; percolating water robs them of
+their soluble salts, reducing even solid granite to a loose mass of
+quartz grains and clay. Plants and animals absorb as food the mineral
+substances of rocks, when they are dissolved in water. They transform
+these food elements into their own body substance, and finally give back
+their dead bodies, the mineral substances of which are freed by decay to
+return to the earth, and become elements of rock again.
+
+The decay of rock is well shown by the materials that accumulate at the
+base of a cliff. Angular fragments of all sizes, but all more or less
+flattened, come from strata of shaly rock, that can be seen jutting out
+far above. A great deal of this sort of material is found mingled with
+the soil of the Northeastern States. Round pebbles in pudding-stone have
+been formed in brook beds and deposited on beaches where they have
+become caked in mud and finally consolidated into rock. If the beach
+chanced to be sandy instead of muddy, a matrix of sandy paste holds the
+larger pebbles in place. Limestone paste cements together the pebbles of
+limestone conglomerates.
+
+In St. Augustine many of the houses are built of coquina rock, a mass of
+broken shells which have become cemented together by lime mud, derived
+from their own decay. On the slopes of volcanoes, rock fragments of all
+kinds are cemented together by the flowing lava. So we see that there
+are pudding-stones of many kinds to be found. If some solvent acid is
+present in the water that percolates through these rocks it may soften
+the cement and thus free the pebbles, reducing the conglomerate again to
+a mere heap of shell fragments, or gravel, or rounded pebbles.
+
+The story of rock formation tells how fire and water, and the two
+combined, have made, and made over, again and again, the substance of
+the earth's crust. Chemical and physical changes constantly tear down
+some portions of the earth to build up others. The constant, combined
+effort of wind and water is to level the earth and fill up the ocean
+bed. Rocks are constantly being formed; the changes that have been going
+on since the world began are still in progress. We can see them all
+about us on any and every day of our lives.
+
+
+
+
+GETTING ACQUAINTED WITH A RIVER
+
+
+I have two friends whose childhood was spent in a home on the banks of a
+noble eastern river. Their father taught the boy and the girl to row a
+boat, and later each learned the more difficult art of managing a canoe.
+On holidays they enjoyed no pleasure so much as a picnic on the
+river-bank at some point that could be reached by rowing. As they grew
+older, longer trips were planned, and the river was explored as far as
+it was navigable by boat or canoe. Last summer when vacation came, these
+two carried out a long-cherished plan to find the beginning of the
+river--to follow it to its source. So they left home, and canoed
+up-stream, until the stream became a brook, so shallow they could go no
+farther. Then they followed it on foot--wading, climbing, making little
+detours, but never losing the little river. At last they came to the
+beginning of it--a tiny rivulet trickled out of the side of a hill,
+filling a wooden keg that formed a basin, where thirsty passers-by could
+stoop and drink. They decided to mark the spring, so that people who
+found it later, and were refreshed by its clear water, might know that
+here was born the greatest river of a great state. But they were not the
+original discoverers. Above the spring, a board was nailed to a tree,
+saying that this is the headwater of the river with the beautiful Indian
+name, Susquehanna.
+
+It was a dry summer, and the overflow of the basin was almost all drunk
+up by the thirsty ground. They could scarcely follow it, except by the
+groove cut by the rivulet in seasons when the flow was greater. They
+followed the runaway brook, through the grass roots, that almost hid it.
+As the ground grew steeper, it hurried faster. Soon it gathered the
+water of other springs, which hurried toward it in small rivulets,
+because its level was lower. Water always seeks the lowest level it can
+find. Sometimes marshy spots were reached where water stood in the holes
+made by the feet of cattle that came there to drink. The water was
+muddy, and seemed to stand still. But it was settling steadily, and at
+one side the little river was found, flowing away with the water it drew
+from the swampy, springy ground. All the mud was gone, now; the water
+was clear. It flowed in a bed with a stony floor, and there were rough
+steps where the water fell down in little sheets, forming a waterfall,
+the first of many that make this river beautiful in the upper half of
+its course. To get from the high level of that hillside spring to the
+low level of the sea, the water has to make a fall of twenty-three
+hundred feet, but it makes the descent gradually. It could not climb
+over anything, but always found a way to get around the rocks and hills
+that stood in its way. When the flat marsh land interfered, the water
+poured in and overflowed the basin at the lowest margin.
+
+In the rocky ground the two explorers found that the stream had widened
+its channel by entering a narrow crevice and wearing away its walls. The
+continual washing of the water wears away stone. Rocks are softened by
+being wet. Streaks of iron in the hardest granite will rust out and let
+the water in. Then the lime in rocks is easily dissolved. Every dead
+leaf the river carried along added an acid to the water, and this made
+easier the process of dissolving the limestone.
+
+Every crumbling rock gives the river tools that it uses like hammer and
+chisel and sandpaper to smooth all the uneven surfaces in its bed, to
+move stumbling blocks, and to dig the bed deeper and wider. The steeper
+the slope is, the faster the stream flows, and the larger the rocks it
+can carry. Rocks loosened from the stream bed are rolled along by the
+current. Then bang! against the rocks that are not loose, and often they
+are able to break them loose. The fine sand is swept along, and its
+sharp points strike like steel needles, and do a great work in polishing
+roughness and loosening small particles from the stream bed. The bigger
+pebbles of the stream have banged against the rock walls, with the same
+effect, smoothing away unevenness and pounding fragments loose, rolling
+against one another, and getting their own rough corners worn away.
+
+The makers of stone marbles learned their business from a brook. They
+cut the stone into cubical blocks, and throw them into troughs, into
+which is poured a stream of running water. The blocks are kept in
+motion, and the grinding makes each block help the rest to grind off the
+eight corners and the twelve ridges of each one. The water becomes muddy
+with the fine particles, just as the drip from a grindstone becomes
+unclean when an axe is ground. Pretty soon all the blocks in the trough
+are changed into globes--the marbles that children buy at the shops when
+marble season comes around.
+
+I suppose if the troughs are not watched and emptied in time, the
+marbles would gradually be ground down to the size of peas, then to the
+size of small bird shot, and finally they would escape as muddy water
+and fine sand grains.
+
+Sure it is that the sandy shores that line most rivers are the remnants
+of hard rocks that have been torn out and ground up by the action of the
+current.
+
+Not very many miles from its first waterfall the stream had grown so
+large that my two friends knew that they would soon find their canoes.
+The plan now was to float down the curious, winding river and to learn,
+if the river and the banks could tell them, just why the course was so
+crooked on the map. They came into a broad, level valley where streams
+met them, coming out of deep clefts between the hills they were leaving
+behind them. The banks were pebbly, but blackened with slimy mud that
+made the water murky. The current swerved from one side to the other,
+sometimes quite close to the bank, where the river turned and formed a
+deep bend. On this side the bank was steep, the roots of plants and
+trees exposed. On the opposite side a muddy bank sloped gently out into
+the stream. Here building up was going on, to offset the tearing down.
+
+The sharp bends are made sharper, once the current is deflected from the
+middle of the stream to one side. At length the loops bend on each other
+and come so near together that the current breaks through, leaving a
+semicircular bayou of still water, and the river's course straightened
+at that place. It must have been in a spring flood that this cut-off was
+made, and, the break once made was easily widened, for the soil is fine
+mud which, when soaked, crumbles and dissolves into muddy water.
+
+Stately and slow that river moves down to the bay, into which it empties
+its load. The rain that falls on hundreds of square miles of territory
+flows into the streams that feed this trunk. The little spring that is
+the headwater of the system is but one of many pockets in the hillsides
+that hold the water that soaks into the ground and give it out by slow
+degrees. Surface water after a rain flows quickly into the streams. It
+is the springs that hold back their supply and keep the rivers from
+running dry in hot weather.
+
+Do they feel now that they know their river? Are they ready to leave it,
+and explore some other? Indeed, no. They are barely introduced to it.
+All kinds of rivers are shown by the different parts of this one. It is
+a river of the mountains and of the lowland. It flows through woods and
+prairies, through rocky passes and reedy flats. It races impetuously in
+its youth, and plods sedately in later life. The trees and the other
+plants that shadow this stream, and live by its bounty, are very
+different in the upland and in the lowland. The scenery along this
+stream shows endless variety. Up yonder all is wild. Down here great
+bridges span the flood, boats of all kinds carry on the commerce between
+two neighbour cities. A great park comes down to the river-bank on one
+side. Canoes are thick as they can paddle on late summer afternoons.
+
+No one can ever really know a river well enough to feel that it is an
+old story. There is always something new it has to tell its friends. So
+my two explorers say, and they know far more about their friendly river
+than I do.
+
+
+
+
+THE WAYS OF RIVERS
+
+
+A canal is an artificial river, built to carry boats from one place to
+another. Its course is, as nearly as possible, a straight line between
+two points. A river, we all agree, is more beautiful than a canal, for
+it winds in graceful curves, in and out among the hills, its waters
+seeking the lowest level, always.
+
+No artist could lay out curves more beautiful than the river forms.
+These curves change from year to year, some slowly, some more rapidly.
+It is not hard to understand just why these changes take place.
+
+Some rivers are dangerous for boating at certain points. The current is
+strong, and there are eddies and whirlpools that have to be avoided, or
+the boat becomes unmanageable. People are drowned each season by
+trusting themselves to rivers the dangerous tricks of which they do not
+know. Deep holes are washed out of the bed of the stream by whirling
+eddies. The pot-holes of which people talk are deep, rounded cavities,
+ground out of the rocky stream-bed by the scouring of sand and loose
+stones driven by whirling eddies in shallow basins. Every year deepens
+each pot-hole until some change in the stream-bed shifts the eddy to
+another place.
+
+No stream finds its channel ready-made; it makes its own, and constantly
+changes it. The current swings to one side of the channel, lifting the
+loose sediment and grinding deeper the bed of the stream. The water lags
+on the opposite side, and sediment falls to the bottom. So the
+building-up of one side is going on at the same time that the
+tearing-down process is being carried on on the other. With the lowering
+of the bed the river swerves toward one bank, and a hollow is worn by
+slow degrees. The current swings into this hollow, and in passing out is
+thrown across the stream to the opposite bank. Here its force wears away
+another hollow; and so it zigzags down-stream. The deeper the hollows,
+the more curved becomes the course, if the general fall is but moderate.
+It is toward the lower courses of the stream that the winding becomes
+more noticeable. The sediment that is carried is deposited at the point
+where the current is least strong, so that while the outcurves become
+sharper by the tearing away of the stream's bank, the incurves become
+sharper by the building up of this bank.
+
+The Mississippi below Memphis is thrown into a wonderful series of
+curves by the erosion and the deposit caused by the current zigzagging
+back and forth from one bank to the other. Gradually the curves become
+loops. The river's current finally jumps across the meeting of the
+curves, and abandons the circular bend. It becomes a bayou or lagoon of
+still water, while the current flows on in the straightened channel.
+All rivers that flow through flat, swampy land show these intricate
+winding channels and many lagoons that have once been curves of the
+river.
+
+No one would ever mistake a river for a lake or any other body of water,
+yet rivers differ greatly in character. One tears its way along down its
+steep, rock-encumbered channel between walls that rise as vertical
+precipices on both sides. The roaming, angry waters are drawn into
+whirlpools in one place. They lie stagnant as if sulking in another,
+then leap boisterously over ledges of rock and are churned into creamy
+foam at the bottom. Outside the mountainous part of its course this same
+river flows broad and calm through a mud-banked channel, cut by
+tributary streams that draw in the water of low, sloping hills.
+
+The Missouri is such a wild mountain stream at its headwaters. We who
+have seen its muddy waters from Sioux City to St. Louis would hardly
+believe that its impetuous and picturesque youth could merge into an old
+age so comfortable and placid and commonplace.
+
+This thing is true of all rivers. They flow, gradually or suddenly, from
+higher to lower levels. To reach the lowest level as soon as possible is
+the end each river is striving toward. If it could, each river would cut
+its bed to this depth at the first stage of its course. Its tools are
+the rocks it carries, great and small. The force that uses these tools
+is the power of falling water, represented by the current of the stream.
+The upper part of a river such as the Missouri or Mississippi engages in
+a campaign of widening and deepening its channel, and carrying away
+quantities of sediment. The lower reaches of the stream flow through
+more level country; the current is checked, and a vast burden of
+sediment is laid down. Instead of tearing away its banks and bottom, the
+river fills up gradually with mud. The current meanders between banks of
+sediment over a bottom which becomes shallower year by year. The Rocky
+Mountains are being carried to the Gulf of Mexico. The commerce of the
+river is impeded by mountain debris deposited as mud-banks along the
+river's lower course.
+
+Many rivers are quiet and commonplace throughout their length. They flow
+between low, rounded hills, and are joined by quiet streams, that occupy
+the separating grooves between the hills. This is the oldest type of
+river. It has done its work. Rainfall and stream-flow have brought the
+level of the land nearly to the level of the stream. Very little more is
+left to be ground down and carried away. The landscape is beautiful, but
+it is no longer picturesque. Wind and water have smoothed away
+unevennesses. Trees and grass and other vegetation check erosion, and
+the river has little to do but to carry away the surface water that
+falls as rain.
+
+But suppose our river, flowing gently between its grassy banks, should
+feel some mighty power lifting it up, with all its neighbour hills and
+valleys, to form a wrinkle in the still unstable crust of the earth.
+Away off at the river's mouth the level may not have changed, or that
+region may have been depressed instead of elevated by the shrinking
+process. Suppose the great upheaval has not severed the upper from the
+lower courses of the stream. With tremendous force and speed, the
+current flows from the higher levels to the lower. The river in the
+highlands strikes hard to reach the level of its mouth. It grinds with
+all its might, and all its rocky tools, upon its bed. All the mud is
+scoured out, and then the underlying rocks are attacked. If these rocks
+are soft and easily worn away, the channel deepens rapidly. One after
+another the alternating layers are excavated, and the river flows in a
+canyon which deepens more and more. As the level is lowered, the current
+of the stream becomes slower and the cutting away of its bed less rapid.
+The stream is content to flow gently, for it has almost reached the old
+level, on which it flowed before the valley became a ridge or
+table-land.
+
+The rivers that flow in canyons have been thousands of years in carving
+out their channels, yet they are newer, geologically speaking, than the
+streams that drain the level prairie country. The earth has risen, and
+the canyons have been carved since the prairies became rolling, level
+ground.
+
+[Illustration: This little pond is a basin hollowed by the same glacier
+that scattered the stones and rounded the hills]
+
+[Illustration: Every stream is wearing away its banks, while trees and
+grass blades are holding on to the soil with all their roots]
+
+The Colorado River flows through a canyon with walls that in places
+present sheer vertical faces a mile in depth, and so smooth that no
+trail can be found by which to reach from top to bottom. The region has
+but slight erosion by wind, and practically none by rain. The local
+rainfall is very slight. So the river is the one force that has acted to
+cut down the rocks, and its force is all expended in the narrow area of
+its own bed. Had frequent rains been the rule on the Colorado plateau,
+the angles of the mesas would have been rounded into hills of the
+familiar kind so constantly a part of the landscape in the eastern half
+of the continent.
+
+The Colorado is an ancient river which has to carry away the store of
+moisture that comes from the Pacific Ocean and falls as snow on the high
+peaks of the Rocky Mountains. Similar river gorges with similar stories
+to tell are the Arkansas, the Platte, and the Yellowstone. All cut their
+channels unaided through regions of little rain.
+
+When the earth's crust is thrown up in mountain folds, and between them
+valleys are formed, the level of rivers is sometimes lowered and the
+rapidity of their flow is checked. A stream which has torn down its
+walls at a rapid rate becomes a sluggish water-course, its current
+clogged with sediment, which it has no power to carry farther. When such
+a river begins to build and obstruct its own waters it bars its progress
+and may form a lake as the outlet of its tributary streams. Many ancient
+rivers have been utterly changed and some obliterated by general
+movements of the earth's crust.
+
+
+
+
+THE STORY OF A POND
+
+
+Look out of the car window as you cross a flat stretch of new prairie
+country, and you see a great many little ponds of water dotting the
+green landscape. Forty years ago Iowa was a good place to see ponds of
+all shapes and sizes. The copious rainfall of the early spring gathered
+in the hollows of the land, and the stiff clay subsoil prevented the
+water from soaking quickly into the ground. The ponds might dry away
+during the hot, dry summer, leaving a baked clay basin, checked with an
+intricate system of cracks. Or if rains were frequent and heavy, they
+might keep full to the brim throughout the season.
+
+Tall bulrushes stood around the margins of the largest ponds, and
+water-lilies blossomed on the surface during the summer. The bass and
+the treble of the spring chorus were made by frogs and toads and little
+hylas, all of which resorted to the ponds to lay their eggs, in coiled
+ropes or spongy masses, according to their various family traditions. On
+many a spring night my zooelogy class and I have visited the squashy
+margins of these ponds, and, by the light of a lantern, seen singing
+toads and frogs sitting on bare hummocks of grass roots that stood
+above the water-line. The throat of each musician was puffed out into a
+bag about the size and shape of a small hen's egg; and all were singing
+for dear life, and making a din that was almost ear-splitting at close
+range. So great was the self-absorption of these singers that we could
+approach them, daze them with the light of the lantern, and capture any
+number of them with our long-handled nets before they noticed us. But it
+was not easy to persuade them to sing in captivity, no matter how many
+of the comforts of home we provided in the school aquariums. So, after
+some very interesting nature studies, we always carried them back and
+liberated them, where they could rejoin their kinsfolk and neighbours.
+
+It was when we were scraping the mud from our rubber boots that we
+realized the character of the bottoms of our prairie ponds. The slimy
+black deposit was made partly of the clay bottom, but largely of
+decaying roots and tops of water plants of various kinds. Whenever it
+rained or the wind blew hard, the bottom was stirred enough to make the
+water muddy; and on the quietest days a pail of pond water had a tinge
+of brown because there were always decaying leaves and other rubbish to
+stain its purity.
+
+The farmers drained the ponds as fast as they were able, carrying the
+water, by open ditches first, and later by underground tile drains, to
+lower levels. Finally these trunk drain pipes discharged the water into
+streams or lakes. To-day a large proportion of the pond areas of Iowa
+has disappeared; the hollow tile of terra-cotta has been the most
+efficient means of converting the waste land, covered by ponds, into
+fertile fields.
+
+But the ponds that have not been drained are smaller than they used to
+be, and are on the straight road to extinction. This process one can see
+at any time by visiting a pond. Every year a crop of reeds and a dozen
+other species of vigorous water plants dies at the top and adds the
+substance of their summer growth to the dust and other refuse that
+gathers in the bottom of the pond. Each spring roots and seeds send up
+another crop, if possible more vigorous than the last, and this top
+growth in turn dies and lies upon the bottom. The pond level varies with
+the rainfall of the years, but it averages a certain depth, from which
+something is each year subtracted by the accumulations of rotting
+vegetable matter in the bottom. Evaporation lowers the water-level,
+especially in hot, dry summers. From year to year the water plants draw
+in to form a smaller circle, the grassy meadow land encroaches on all
+sides. The end of the story is the filling up of the pond basin with the
+rotting substance of its own vegetation. This is what is happening to
+ponds and inland marshes by slow degrees. The tile drain pipes
+obliterate the pond in a single season. Nature is more deliberate. She
+may require a hundred years to fill up a single pond which the farmer
+can rid himself of by a few days of work and a few rods of tiling.
+
+
+
+
+THE RIDDLE OF THE LOST ROCKS
+
+
+Outside of my window two robins are building a nest in the crotch of a
+blossoming red maple tree. And just across the hedge, men are digging a
+big square hole in the ground--the cellar of our neighbour's new house.
+It looks now as if the robins would get their house built first, for
+they need but one room, and they do not trouble about a cellar. I shall
+watch both houses as they grow through the breezy March days.
+
+The brown sod was first torn up by a plough, which uncovered the red New
+Jersey soil. Two men, with a team hitched to a scraper, have carried
+load after load of the loose earth to a heap on the back of the lot,
+while two other men with pickaxes dug into the hard subsoil, loosening
+it, so that the scraper could scoop it up.
+
+This subsoil is heavy, like clay, and it breaks apart into hard clods.
+At the surface the men found a network of tree roots, about which the
+soil easily crumbled. Often I hear a sharp, metallic stroke, unlike the
+dull sound of the picks striking into the earth. The digger has struck a
+stone, and he must work around it, pry it up and lift it out of the way.
+A row of these stones is seen at one side of the cellar hole, ranged
+along the bank. They are all different in size and shape, and red with
+clay, so I can't tell what they are made of. But from this distance I
+see plainly that they are irregular in form and have no sharp corners.
+The soil strewn along the lot by the scraper is full of stones, mostly
+irregular, but some rounded; some are as big as your head, others grade
+down to the sizes of marbles.
+
+When I went down and examined this red earth, I found pebbles of all
+shapes and sizes, gravel in with the clay, and grains of sand. This
+rock-sprinkled soil in New Jersey is very much like soil which I know
+very well in Iowa; it looks different in colour, but those pebbles and
+rock fragments must be explained in the same way here as there.
+
+These are not native stones, the outcrop of near-by hillsides, but
+strangers in this region. The stones in Iowa soil are also imported.
+
+The prairie land of Iowa has not many big rocks on the surface, yet
+enough of them to make trouble. The man who was ploughing kept a sharp
+lookout, and swung his plough point away from a buried rock that showed
+above ground, lest it should break the steel blade. One of the farmer's
+jobs for the less busy season was to go out with sledge and dynamite
+sticks, and blast into fragments the buried boulders too large to move.
+Sometimes building a hot fire on the top of it, and throwing on water,
+would crack the stubborn "dornick" into pieces small enough to be loaded
+on stone-boats.
+
+I remember when the last giant boulder whose buried bulk scarcely showed
+at the surface, was fractured by dynamite. Its total weight proved to be
+many tons. We hauled the pieces to the great stone pile which furnished
+materials for walling the sides of a deep well and for laying the
+foundation of the new house. Yet for years stones have been
+accumulating, all of them turned out of the same farm, when pastures and
+swampy land came under the plough.
+
+Draw a line on the map from New York to St. Louis, and then turn
+northward a little and extend it to the Yellowstone Park. The
+boulder-strewn states lie north of this line, and are not found south of
+it, anywhere. Canada has boulders just like those of our Northern
+States. The same power scattered them over all of the vast northern half
+of North America and a large part of Europe.
+
+What explanation is there for this extensive distribution of unsorted
+debris?
+
+
+
+
+THE QUESTION ANSWERED
+
+
+The rocks tell their own story, partly, but not wholly. They told just
+enough to keep the early geologists guessing; and only very recently has
+the guessing come upon the truth.
+
+These things the rocks told:
+
+1. We have come from a distance.
+
+2. We have had our sharp corners worn off.
+
+3. Many of us have deep scratches on our sides.
+
+4. At various places we have been dumped in long ridges, mixed with much
+earth.
+
+5. A big boulder is often balanced on another one.
+
+The first thing the geologist noted was the fact that these boulders are
+strangers--that is, they are not the native rocks that outcrop on
+hillsides and on mountain slopes near where they are found. Far to the
+north are beds of rock from which this debris undoubtedly came. Could a
+flood have scattered them as they are found? No, for water sorts the
+rock debris it deposits, and it rounds and polishes rock fragments,
+instead of scratching and grooving them and leaving them angular, as
+these are.
+
+Professor Agassiz went to Switzerland and studied the glaciers. He found
+unsorted rock fragments where the glacier's nose melted, and let them
+fall. They were worn and scratched and grooved, by being frozen into the
+ice, and dragged over the rocky bed of the stream. The rocky walls of
+the valley were scored by the glacier's tools. Rounded domes of rock
+jutted out of the ground, in the paths of the ice streams, just like the
+granite outcrop in Central Park in New York, and many others in the
+region of scattered boulders.
+
+After long studies in Europe and in North America, Professor Agassiz
+declared his belief that a great ice-sheet once covered the northern
+half of both countries, rounding the hills, scooping out the valleys and
+lake basins, and scattering the boulders, gravel, and clay, as it
+gradually melted away.
+
+The belief of Professor Agassiz was not accepted at once, but further
+studies prove that he guessed the riddle of the boulders. The rich soil
+of the Northern States is the glacial drift--the mixture of rock
+fragments of all sizes with fine boulder clay, left by the gradual
+melting of the great ice-sheet as it retreated northward at the end of
+the "Glacial Epoch."
+
+
+
+
+GLACIERS AMONG THE ALPS
+
+
+Switzerland is a little country without any seacoast, mountainous, with
+steep, lofty peaks, and narrow valleys. The climate is cool and moist,
+and snow falls the year round on the mountain slopes. A snow-cap covers
+the lower peaks and ridges. Above the level of nine thousand feet the
+bare peaks rise into a dry atmosphere; but below this altitude, and
+above the six thousand-foot mark, lies the belt of greatest snowfall.
+Peaks between six and nine thousand feet high are buried under the
+Alpine snow-field, which adds thickness with each storm, and is drained
+away to feed the rushing mountain streams in the lower valleys.
+
+The snow that falls on the steep, smooth slope clings at first; but as
+the thickness and the weight of these snow banks increase, their hold on
+the slope weakens. They may slip off, at any moment. The village at the
+foot of the slope is in danger of being buried under a snow-slide, which
+people call an avalanche. "Challanche" is another name for it. The
+hunter on the snow-clad mountains dares not shout for fear that his
+voice, reechoing among the silent mountains, may start an avalanche on
+its deadly plunge into the valley.
+
+On the surface of the snow-field, light snow-flakes rest. Under them the
+snow is packed closer. Deeper down, the snow is granular, like pellets
+of ice; and still under this is ice, made of snow under pressure. The
+weight of the accumulated snow presses the underlying ice out into the
+valleys. These streams are the glaciers--rivers of ice.
+
+The glaciers of the Alps vary in length from five to fifteen miles, from
+one to three miles in width, and from two hundred to six hundred feet in
+thickness. They flow at the rate of from one to three feet a day, going
+faster on the steeper slopes.
+
+It is hard to believe that any substance as solid and brittle as ice can
+flow. Its movement is like that of stiff molasses, or wax, or pitch. The
+tremendous pressure of the snow-field pushes the mass of ice out into
+the valleys, and its own weight, combined with the constant pressure
+from behind, keeps it moving.
+
+The glacier's progress is hindered by the uneven walls and bed of the
+valley, and by any decrease in the slope of the bed. When a flat, broad
+area is reached, a lake of ice may be formed. These are not frequent in
+the Alps. The water near the banks and at the bottom of a river does not
+flow as swiftly as in the middle and at the surface of the stream. The
+flow of ice in a glacier is just so. Friction with the banks and bottom
+retards the ice while the middle parts go forward, melting under the
+strain, and freezing again. There is a constant readjusting of
+particles, which does not affect the solidity of the mass.
+
+The ice moulds itself over any unevenness in its bed if it cannot remove
+the obstruction. The drop which would cause a small waterfall in a
+river, makes a bend in the thick body of the ice river. Great cracks,
+called _crevasses_, are made at the surface, along the line of the bend.
+The width of the V-shaped openings depends upon the depth of the glacier
+and the sharpness of the bend that causes the breaks.
+
+Rocky ridges in the bed of the ice-stream may cause crevasses that run
+lengthwise of the glacier. Snow may fill these chasms or bridge them
+over. The hunter or the tourist who ventures on the glacier is in
+constant danger, unless he sees solid ice under him. Men rope themselves
+together in climbing over perilous places, so that if one slips into a
+crevasse his mates can save him.
+
+A glacier tears away and carries away quantities of rock and earth that
+form the walls of its bed. As the valley narrows, tremendous pressure
+crowds the ice against the sides, tearing trees out by the roots and
+causing rock masses to fall on the top of the glacier, or to be dragged
+along frozen solidly into its sides. The weight of the ice bears on the
+bed of the glacier, and its progress crowds irresistibly against all
+loose rock material. The glacier's tools are the rocks it carries frozen
+into its icy walls and bottom. These rocks rub against the walls,
+grinding off debris which is pushed or carried along. No matter how
+heavy the boulders are that fall in the way of the ice river, the ice
+carries them along. It cannot drop them as a river of water would do.
+Slowly they travel, and finally stop where the nose of the glacier melts
+and leaves all debris that the mountain stream, fed by the melting of
+the ice, cannot carry away.
+
+The bedrock under a glacier is scraped and ground and scored by the
+glacier's tools--the rock fragments frozen into the bottom of the ice.
+These rocks are worn away by constant grinding, just as a steel knife
+becomes thin and narrow by use. Scratches and scorings and polished
+surfaces are found in all rocks that pass one another in close contact.
+Its worn-out tools the glacier drops at the point where its ice melts.
+This great, unsorted mass of rock meal and coarser debris the stream is
+gradually scattering down the valley.
+
+The name "moraine" has been given to the earth rubbish a glacier
+collects and finally dumps. The _top moraine_ is at the surface of the
+ice. The _lateral moraines_, one at each side, are the debris gathered
+from the sides of the valley. The _ground moraine_ is what debris the
+ice pushes and drags along on the bottom. The _terminal moraine_ is the
+dumping-ground of this mass of material, where the ice river melts.
+
+Glaciers, like other rivers, often have tributary streams. A _median
+moraine_, seen as a dark streak running lengthwise on the surface of a
+glacier, means that two branch glaciers have united to form this one. Go
+back far enough and you will reach the place where the two streams come
+together. The two lateral moraines that join form the middle line of
+debris, the median moraine. Three ice-streams joined produce two top
+moraines. They locate the lateral moraines of the middle glacier.
+
+The surface of a glacier is often a mass of broken and rough ice,
+forming a series of pits and pinnacles that make crossing impossible.
+The sun melts the surface, forming pools and percolating streams of
+water, that honeycomb the mass. Underneath, the ice is tunnelled, and a
+rushing stream flows out under the end of the glacier. It is not clear,
+but black with mud, called _boulder clay_, or _till_, made of ground
+rock, and mixed with fragments of all shapes and sizes. This is the meal
+from the glacier's mill, dumped where the water can sift it.
+
+"Balanced rocks" are boulders, one upon another, that once lay on a
+glacier, and were left in this strange, unstable position when the
+supporting ice walls melted away from them. In Bronx Park in New York
+the "rocking stone" always attracts attention. The glacier that lodged
+it there, also rounded the granite dome in Central Park and scattered
+the rock-strewn boulder clay on Long Island. Doubtless in an earlier day
+the edges of this glacier were thrust out into the Atlantic, not far
+from the Great South Bay, and icebergs broke off and floated away.
+
+[Illustration: Potsdam sandstone showing ripple marks]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Glacial striae on Lower Helderberg limestone]
+
+[Illustration: Glacial grooves in the South Meadow, Central Park, New
+York]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Mt. Tom, West 83d St., New York]
+
+Glaciers are small to-day compared with what they were long ago, in
+Europe and in America. The climate became warmer, and the ice-cap
+retreated. Old moraines show that the ice rivers of the Alps once came
+much farther down the valleys than they do now. Smooth, deeply scored
+domes of rock, the one in Central Park and the bald head of Mount Tom,
+are just like those that lie in Alpine valleys from which the glaciers
+have long ago retreated. There are old moraines far up the sides of
+valleys, showing that once the glaciers were far deeper than now. No
+other power could have brought rocks from strata higher up the
+mountains, and lodged them thus.
+
+Nearer home, Mt. Shasta and Mt. Rainier still have glaciers that have
+dwindled in size, until they bear little comparison to the gigantic
+ice-streams that once filled the smooth beds their puny successors flow
+into. Remnants of glaciers lie in the hollows of the Sierras. We must go
+north to find the snow-fields of Alaska and glaciers worthy to be
+compared with those ancient ice rivers whose work is plainly to be seen,
+though they are gone.
+
+
+
+
+THE GREAT ICE-SHEET
+
+
+Greenland is green only along its southern edge, and only in summer, so
+its name is misleading. It is a frozen continent lying under a great
+ice-cap, which covers 500,000 square miles and is several thousand feet
+in thickness. The top of this icy table-land rises from five thousand to
+ten thousand feet above the sea-level. The long, cold winters are marked
+by great snowfall, and the drifts do not have time to melt during the
+short summer; and so they keep getting deeper and deeper. Streams of ice
+flow down the steeps into the sea, and break off by their weight when
+they are pushed out into the water. These are the icebergs which float
+off into the North Atlantic, and are often seen by passengers on
+transatlantic steamers.
+
+Long ago Greenland better deserved its name. Explorers who have climbed
+the mountain steeps that guard the unknown ice-fields of the interior
+have discovered, a thousand feet above the sea-level, an ancient beach,
+strewn with shells of molluscs like those which now inhabit salt water,
+and skeletons of fishes lie buried in the sand. It is impossible to
+think that the ocean has subsided. The only explanation that accounts
+for the ancient beach, high and dry on the side of Greenland's icy
+mountain is that the continent has been lifted a thousand feet above its
+former level. This is an accepted fact.
+
+We know that climate changes with changed altitude as well as latitude.
+Going up the side of a mountain, even in tropical regions, we may reach
+the snow-line in the middle of summer. Magnolia trees and tree ferns
+once grew luxuriantly in Greenland forests. Their fossil remains have
+been found in the rocks. This was long before the continent was lifted
+into the altitude of ice and snow. And it is believed that the climate
+of northern latitudes has become more severe than formerly from other
+causes. It is possible that the earth's orbit has gradually changed in
+form and position.
+
+If Greenland should ever subside until the ancient beach rests again at
+sea-level, the secrets of that unknown land would be revealed by the
+melting of the glacial sheet that overspreads it. Possibly it would turn
+out to be a mere flock of islands. We can only guess. North America had,
+not so long ago, two-thirds of its area covered with an ice-sheet like
+that of Greenland, and a climate as cold as Greenland's. At this time
+the land was lifted two to three thousand feet higher than its present
+level. All of the rain fell as snow, and the ice accumulated and became
+thicker year by year. Instead of glaciers filling the gorges, a great
+ice flood covered all the land, and pushed southward as far as the Ohio
+River on the east and Yellowstone Park in the west. The Rocky Mountains
+and some parts of the Appalachian system accumulated snow and formed
+local glaciers, separated from the vast ice-sheet.
+
+The unstable crust of the earth began to sink at length, and gradually
+the ice-sheet's progress southward was checked, and it began to recede
+by melting. All along the borders of this great fan-shaped ice-field
+water accumulated from the melting, and flooded the streams which
+drained it to the Atlantic and the Gulf. Icebergs broken off of the edge
+of the retiring ice-sheet floated in a great inland sea. The land sank
+lower and lower until the general level was five hundred to one thousand
+feet lower than it now is. The climate became correspondingly warm, and
+the icebergs melted away. Then the land rose again, and in time the
+inland sea was drained away into the ocean, except for the waters that
+remained in thousands of lakes great and small that now occupy the
+region covered by the ice.
+
+Ancient sea beaches mark the level of high water at the time that the
+flood followed the melting ice. On the shores of Lake Champlain, but
+nearly five hundred feet higher than the present level of the lake,
+curious geologists have found many kinds of marine shells on a
+well-marked old sea beach. The members of one exploring party in the
+same region were surprised and delighted to come by digging upon the
+skeleton of a whale that had drifted ashore in the ancient days when
+the inland sea joined the Atlantic.
+
+Lake Ontario's ancient beach is five hundred feet above the present
+water-level; Lake Erie's is two hundred fifty feet above it; Lake
+Superior's three hundred thirty feet higher than the present beach. No
+doubt when the water stood at the highest level, the Great Lakes formed
+one single sheet of water which settled to a lower level as the rivers
+flowing south cut their channels deep enough to draw off the water
+toward the Gulf. Lake Winnipeg is now the small remnant of a vast lake
+the shores of which have been traced. The Minnesota River finally made
+its way into the Mississippi and drained this great area the stranded
+beaches of which still remain. The name of Agassiz has been given to the
+ancient lake formed by the glacial flood and drained away thousands of
+years ago but not until it had built the terraced beach which locates it
+on the geological map of the region.
+
+When the ice-sheet came down from the north it dragged along all of the
+soil and loose rock material that lay in its path. With the boulders
+frozen into its lower surface it scratched and grooved the firm bedrock
+over which it slid, and rounded it to a smooth and billowy surface. The
+progress of the ice-sheet was southward, but it spread like a fan so
+that its widening border turned to east and west.
+
+When it reached its southernmost limit and began to melt, it laid down a
+great ridge of unsorted rock material, remnants of which remain to this
+day,--the terminal moraine of the ancient ice-sheet. The line of this
+ancient deposit starts on Long Island, crosses New Jersey and
+Pennsylvania, then dips southward, following the general course of the
+Ohio River to its mouth, forming bluffs in southern Ohio, Indiana, and
+Illinois. The line bends upward as it crosses central Missouri, a corner
+of Kansas, and eastern Nebraska, parallel with the course of the
+Missouri.
+
+As the ice-sheet melted, boulders were dropped all over the Northern
+States and Canada. These were both angular and rounded. In some places
+they are scattered thickly over the surface and are so numerous as to be
+a great hindrance to agriculture. In many places great boulders of
+thousands of tons weight are perched on very slight foundations, just
+where they lodged when the ice went off and left them, after carrying
+them hundreds of miles. Around them are scattered quantities of loose
+rock material, not scored or ground as are those which were carried on
+the under-surface of the glacial ice. These unscarred fragments rode on
+the top of the ice. They were a part of the top moraine of the glacial
+sheet.
+
+The finest material deposited is rock meal, ground by the great glacial
+mill, and called "boulder clay." It is a stiff, dense, stony paste in
+which boulders of all sizes, gravel, pebbles, and cobblestones are
+cemented.
+
+The "drift" of the ice-sheet is the rubbish, coarse and fine, it left
+behind as it retreated. Below the Ohio River there is a deep soil
+produced by the decay of rocks that lie under it. North of Ohio is
+spread that peculiar mixture of earth and rock fragments which was
+transported from the north and spread over the land which the ice-sheet
+swept bare and ground smooth and polished.
+
+The drift has been washed away in places by the floods that followed the
+ice. Granite domes are thus exposed, the grooves and scratches of which
+tell in what direction the ice flood was travelling. Miles away from
+that scored granite, but in the same direction as the scratches,
+scattered fragments of the same foundation rock cover fields and
+meadows. Thus, much of the drift material can be traced to its original
+home, and the course of the ice-sheet can be determined. Many immense
+boulders the home of which was in the northern highlands of Canada rode
+southward, frozen into icebergs that floated in the great inland sea.
+Great quantities of debris were added to the original glacial drift
+through the agency of these floating ice masses, which melted by slow
+degrees.
+
+
+
+
+FOLLOWING SOME LOST RIVERS
+
+
+What would you think if the boat in which you were floating down a
+pleasant river should suddenly grate upon sand, and you should look over
+the gunwale and find that here the waters sank out of sight, the river
+ended? I believe you would rub your eyes, and feel sure that you were
+dreaming. Do not all rivers flow along their beds, growing larger with
+every mile, and finally empty their waters into a sea, or bay, or lake,
+or flow into some larger stream? This is the way of most rivers, but
+there are exceptions. In the Far West there are some great rivers that
+absolutely disappear before they reach a larger body of water. They
+simply sink away into the sand, and sometimes reappear to finish their
+courses after flowing underground for miles. Do you know the name of one
+great western river of which I am thinking? Is there any stream in your
+neighbourhood which has such peculiar ways?
+
+Down in Kentucky there is a region where, it is said, one may walk fifty
+miles without crossing running water. In the middle of our country, in
+the region of plentiful rainfall, and in a state covered with beautiful
+woodlands and famous for blue grass and other grain crops, it is
+amazing that, over a large area, brooks and larger streams are lacking.
+In most of the state there is plenty of water flowing in streams like
+those in other parts of the eastern half of the United States. In the
+near neighbourhood of this peculiar section of the state the streams
+come to an end suddenly, pouring their water into funnel-shaped
+depressions of the ground called sink-holes. After a heavy rain the
+surface water, accumulating in rivulets, may also be traced to small
+depressions which seem like leaks in the earth's crust, into which the
+water trickles and disappears.
+
+It must have been noticed by the early settlers who came over the
+mountains from the eastern colonies, and settled in the new, wild, hilly
+country, which they called Kentucky. The first settlers built their log
+cabins along the streams they found, and shot deer and wild turkey and
+other game that was plentiful in the woods. The deer showed them where
+salt was to be found in earthy deposits near the streams; for salt is
+necessary to every creature. Deer trails led from many directions to the
+"salt licks" which the wild animals visited frequently.
+
+Perhaps the same pioneers who dug the salt out of the earth found
+likewise deposits of _nitre_, called also _saltpetre_, a very precious
+mineral, for it is one of the elements necessary in the manufacture of
+gunpowder. With the Indians all about him, and often showing themselves
+unfriendly, the pioneer counted gunpowder a necessity of life. He relied
+on his gun to defend and to feed his family. There were men among those
+first settlers who knew how to make gunpowder, and saltpetre was one of
+the things that had to be carried across the mountains into Kentucky,
+until they found it in the hills. No wonder that prospectors went about
+looking for nitre beds in the overhanging ledges of rocks along
+stream-beds. In such situations the deposits of nitre were found. The
+earth was washed in troughs of running water to remove the clayey
+impurity. After a filtering through wood-ashes, the water which held the
+nitre in solution was boiled down, and left to evaporate, after which
+the crystals of saltpetre remained.
+
+Solid masses of saltpetre weighing hundreds of pounds were sometimes
+found in protected corners under shelving rocks. It was no doubt in the
+fascinating hunt for lumps of this pure nitre that the early prospectors
+discovered that the streams which disappeared into the sink-holes made
+their way into caverns underground. Digging in the sides of ravines
+often made the earthy wall cave in, and the surprised prospector stood
+at the door of a cavern. The discoverer of a cave had hopes that by
+entering he might find nitre beds richer than those he could uncover on
+the surface, and this often turned out to be true. The hope of finding
+precious metals and beds of iron ore also encouraged the exploration of
+these caves. By the time the war of 1812 was declared, the mining of
+saltpetre was a good-sized industry in Kentucky. Most of the mineral was
+taken out of small caves, and shipped, when purified, over the
+mountains, on mule-back by trails, and in carts over good roads that
+were built on purpose to bring this mineral product to market. As long
+as war threatened the country, the Government was ready to buy all the
+saltpetre the Kentucky frontiersmen could produce. And the miners were
+constantly in search of richer beds that promised better returns for
+their labour.
+
+It was this search that led to the exploration of the caves discovered,
+although the explorer took his life in his hands when he left the
+daylight behind him and plunged into the under-world.
+
+Not all lost rivers tell as interesting stories or reveal as valuable
+secrets as did those the neighbours of Daniel Boone traced along their
+dark passages underground, and finally saw emerge as hillside springs,
+in many cases, to feed Kentucky rivers. But it is plain that no river
+sinks from sight unless it finds porous or honeycombed rocks that let it
+through. The water seeks the nearest and easiest route to the sea. Its
+weight presses toward the lowest level, always. The more water absorbs
+of acid, the more powerfully does it attack and carry away the substance
+of lime rocks through which it passes.
+
+
+
+
+THE MAMMOTH CAVE OF KENTUCKY
+
+
+There is no more fertile soil in the country than that of the famous
+blue grass region of Kentucky. The surface soil rests upon a deep
+foundation of limestone rocks, and very gradually the plant food locked
+up in these underlying strata is pulled up to the surface by the soil
+water, and greedily appropriated by the roots of the plants.
+
+Part of the water of the abundant rainfall of this region soaks into the
+layers of the lime rock, carrying various acids in solution which give
+it power to dissolve the limestone particles, and thus to make its way
+easily through comparatively porous rock to the very depths of the
+earth. So it has come about that the surface of the earth is undermined.
+Vast empty chambers have been carved by the patient work of trickling
+water, which has carried away the lime that once formed solid and
+continuous layers of the earth's crust. We must believe that the work
+has taken thousands of years, at least, for no perceptible change has
+come to these wonderful caves since the discovery and exploration of
+them a century and more ago.
+
+The streams that flow into the region of these caves disappear suddenly
+into sink-holes and flow through caverns. After wearing away their
+subterranean channels, leaping down from one level to another, forming
+waterfalls and lakes, some emerge finally through hillsides in the form
+of springs.
+
+The cavern region of Kentucky covers eight thousand square miles. The
+underground chambers found there are in the limestone rock which varies
+from ten to four hundred feet in thickness, and averages a little less
+than two hundred feet. Over this territory the number of sink-holes
+average one hundred to the square mile; and the streams that have poured
+their water into these basins have made a network of open caverns one
+hundred thousand miles in length.
+
+A great many small caverns have been thoroughly explored and are famous
+for their beauty. The Diamond Cave is one of the most splendid, for it
+is lined with walls and pillars of alabaster that sparkle in the
+torchlight with crystals that look like veritable diamonds. Beautiful
+springs and waterfalls are found in many caves, but the grandest of all
+is the Mammoth Cave, beside which no other is counted worthy to be
+compared.
+
+Great tales the miners told of the wonder and the beauty of these
+caverns, the walls of which were supported by arching alabaster columns
+and wonderful domes, of indescribable beauty of form and colouring. In
+1799, the year that Washington died, a pioneer discovered the entrance
+to a cave, the size and beauty of which surpassed anything he had seen
+before. After exploring it for a short distance he returned home and
+took his whole family with him to enjoy the first view of the wonderful
+cavern he had discovered. They carried pine knots and a lighted torch,
+by which they made their way for some distance, but the torch was
+accidentally extinguished and they groped their way in darkness and
+missed the entrance. Without anything to guide them, they wandered in
+darkness for three days, and were almost dead when at last they stumbled
+upon the exit. This is the doorway of the Mammoth Cave of Kentucky, one
+of the wonders of the world.
+
+This was a terrible experience. The next persons who attempted to
+explore the new cave were better provisioned against the chance of
+spending some time underground. The pioneers found rich deposits of
+nitre in the "Great Cave," as they called it. Scientists visited it and
+explored many of its chambers. The reputation of this cavern has been
+spread by thousands of visitors who have come from all over the world to
+see it. The cave has not yet been completely explored. The regular
+tours, on which the guides conduct visitors, cover but a small part of
+the one hundred and fifty miles measured by the two hundred or more
+avenues. The passages wind in and out, crossing each other, sometimes at
+different levels, and forming a network of avenues in which the
+unaccustomed traveller would surely be lost. The old guides know every
+inch of their regular course, and their quaint and edifying talk adds
+greatly to the pleasure of the visitors.
+
+From the hotel, parties are organized for ten o'clock in the morning and
+seven o'clock in the evening. Each visitor is provided with a lard-oil
+lamp. The guide carries a flask of oil and plenty of matches. No special
+garb is necessary, though people usually dress for comfort, and wear
+easy shoes. The temperature of the cave is uniform winter and summer,
+varying between fifty-three and fifty-four degrees Fahrenheit.
+
+The cave entrance is an arch of seventy-foot span in the hillside. A
+winding flight of seventy stone steps leads the party around a
+waterfall, into a great chamber under the rocks. Then the way goes
+through a narrow passage, where the guide unlocks an iron gate to let
+them in. The visitors now leave all thoughts of daylight behind, for the
+breeze that put out their lights as they entered the cave is past, and
+they stand in the Rotunda, a vast high-ceilinged chamber, silent and
+impressive, with walls of creamy limestone, encrusted with gypsum, which
+has been stained black by manganese. From the vestibule on, each passage
+and each room has a name, based upon some historic event or some fancied
+resemblance. The Giant's Coffin is a great kite-shaped rock lying in one
+of the rooms of the cave. The Star Chamber has a wonderful
+crystal-studded dome in which the guide produces the effect of a sunrise
+by burning coloured lights. Bonfires built at suitable points produce
+wonderful shadow effects, which are like nothing else in the world. The
+old saltpetre vats which the visitors pass in taking the "Long Route"
+through the cave, point them back to the days during the War of 1812,
+when this valuable mineral was extracted from the earth in the floor of
+the cave. The industry greatly enriched the thrifty owners of the cave,
+but the works were abandoned after peace was declared.
+
+It must be a wonderful experience to walk steadily for nine hours over
+the Long Route, for so pure is the air and so wonderful is the scenery
+that people rarely complain of fatigue when the experience is over.
+There is no dust on the floors of these subterranean chambers, and they
+are not damp except near places where water trickles, here and there, in
+rivulets and cascades. Pools of water at the bottoms of pits so deep
+that a lighted torch requires several seconds to reach the bottom, and
+rivers and lakes of considerable size, show where some of the surface
+water goes to. A strange underground suction creates whirlpools in some
+of these streams. People go in boats holding twenty passengers for a row
+on Echo River, and the guide dips up with a net the blind fish and
+crayfish and cave lizards which inhabit these subterranean waters. The
+echoes in various chambers of the Mammoth Cave are remarkable. In some
+of them a song by a single voice comes back with full chords, as if
+several voices carried the different parts. The single notes of flute
+and cornet are returned with the same beautiful harmonies. A pistol shot
+is given back a dozen times, the sound rebounding like a ball from rock
+to rock of the arching walls. The vibrations of the water made by the
+rower's paddles reecho in sounds like bell notes, and they are
+multiplied into harmonies that suggest the chimes in the belfry of a
+cathedral.
+
+The walls of various chambers differ from each other according to the
+minerals that compose them. Some are creamy white limestone arches, some
+are walled with black gypsum, some are hung with great curtains of
+stalagmites, solid but suggesting the lightness and grace of folds of
+crepe. Under such hangings the floor is built up in stalactites. The
+mineral-laden water, the constant drip of which has produced a hanging,
+icicle-like stalagmite, has built up the stalactite to meet it.
+
+Probably nothing is more beautiful than the flower-like crystals that
+bloom all over the walls of a chamber called "Mary's Bower." The floor,
+even, sparkles with jewels that have fallen from the wonderful and
+delicate flower clusters built from deposits of the lime-laden water
+which goes on building and replacing the bits that fall. "Martha's
+Vineyard" is decorated with nodules, like bunches of grapes, that
+glisten as if the dew were on them. The white gypsum in some caves makes
+the walls look as if they were carved out of snow. Still others have
+clear, transparent crystals that make them gleam in the torches' light
+as if the walls were encrusted with diamonds.
+
+The cave region of Indiana is also famous. The great Wyandotte Cave in
+Crawford County is the most noted of many similar caverns. In some of
+the chambers, bats are found clinging to the ceiling, heads downward,
+like swarms of bees. The caverns of Luray, in Virginia, are complex and
+wonderful in their structure, and famous for the beautiful stalactites
+and stalagmites they contain. But there is no cave in this country so
+wonderful and so grand in its dimensions as the Mammoth Cave in
+Kentucky.
+
+
+
+
+LAND-BUILDING BY RIVERS
+
+
+Once a year, when the rainy season comes in the mountainous country
+south of Egypt, the old Nile floods its banks and spreads its slimy
+waters over the land, covering the low plains to the very edge of the
+Sahara Desert. The people know it is coming, and are prepared for this
+flood. We should think such an overflow of our nearest river a monstrous
+calamity, but the Egyptians bless the river which blesses them. They
+know that without the Nile's overflow their country would be added to
+the Desert of Sahara. In a short time after the overflow, the river
+reaches its highest point and begins to ebb. Canals lying parallel to
+its course are filled with water which is saved for use in the hot, dry
+summer. As the flood goes down, a deposit of slimy mud lies as a rich
+fertilizer on the land. It is this and the water which the earth has
+absorbed that make Egypt one of the most fertile agricultural countries
+in the world.
+
+The region covered by the Nile's overflow is the flood plain of this
+river. On this plain the Pyramids, the Sphinx, and other famous
+monuments of Egypt stand. The statue of Rameses II. built 3,000 years
+ago, has its base buried nine feet deep in the rich soil made of Nile
+sediment. A well dug in this region goes through forty feet of this soil
+before striking the underlying sand. How many years ago did the first
+Nile overflow take place? We may begin our calculation by finding out
+the average yearly deposit. It is a slow process that accumulates but
+nine feet in 3,000 years. If you were in Egypt when the Nile went back
+into its banks, you would see that the scum it leaves in a single
+overflow adds not a great deal to the thickness of the soil. Possibly
+floods have varied in their deposits from year to year, so that any
+calculation of the time it took to build that forty feet of surface soil
+must be but a rough estimate. This much we know: it has been an
+uninterrupted process which has taken place within the present
+geological epoch, "the Age of Man."
+
+Not all the rich sediment the Nile brings down is left on the level
+flood plain along its course. A vast quantity is dumped at the river's
+mouth, where the tides of the Mediterranean check the river's current.
+Thus the great delta is formed. The broad river splits into many mouths
+that spread out like a fan and build higher and broader each year the
+mud-banks between the streams. Upper Egypt consists of river swamps.
+Lower Egypt, from Cairo to the sea, is the delta built by the river
+itself on sea bottom. From the head of the delta, where the river
+commences to divide, to the sea, is an area of 10,000 square miles made
+out of material contributed by upper Egypt, and built by the river.
+Layer upon layer, it is constantly forming, but most rapidly during the
+season of floods.
+
+Coming closer home, let us look at the map of the Mississippi Valley.
+Begin as far north as St. Louis. For the rest of its course the
+Mississippi River flows through a widening plain of swamp land, flooded
+in rainy seasons. Through this swampy flood plain the river meanders;
+its current, heavily loaded with sediment, swings from one side to the
+other of the channel, building up here, wearing away there, and
+straightening its course when the curves become so sharp that their
+sides meet. Then the current breaks through the thin wall, and a bayou
+of still water is left behind.
+
+Below Baton Rouge the Mississippi breaks into many mouths, that spread
+and carry the water of the great river into the Gulf of Mexico. The Nile
+delta is triangular, like delta, [Greek: D], the fourth letter of the
+Greek alphabet; but the Mississippi's delta is very irregular. The main
+mouth of the river flows fifty miles out into the Gulf between
+mud-banks, narrow and low. At the tip it branches into several streams.
+
+From the mouth of the Ohio to the Gulf, the Mississippi flood plain
+covers 30,000 square miles. Over this area, sediment to an average depth
+of fifty feet has been laid down. In earlier times the river flooded
+this whole area, when freshets swelled its tributaries in the spring.
+The flood plain then became a sea, in the middle of which the river's
+current flowed swiftly. The slow-flowing water on each side of the main
+current let go of its burden of sediment and formed a double ridge.
+Between these two natural walls the main river flowed. When its level
+fell, two side streams, running parallel with the main river drained the
+flood plains on each side into the main tributaries to right and left.
+These natural walls deposited when the river was in flood are called
+_levees_. Each heavy flood builds them higher, and the bed of the stream
+rises by deposits of sediment. So it happens that the level of the river
+bed is higher than the level of its flood plain.
+
+This is an interesting fact in geology. But the people who have taken
+possession of the rich flood plain of the Mississippi River, who have
+built their homes there, drained and cultivated the land, and built
+cities and towns on the areas reclaimed from swamps, recognize the
+elevation of the river bed as the greatest danger that threatens them.
+Suppose a flood should come. Even if it does not overflow the levees, it
+may break through the natural banks and thus overflow the cities and the
+farm lands to left and right.
+
+Instead of living in constant fear of such a calamity, the people of the
+Mississippi flood plain have sought safety by making artificial levees,
+to make floods impossible. These are built upon the natural levees. As
+the river bed rises by the deposit of mud, the levees are built higher
+to contain the rising waters. No longer does the rich soil of the
+Mississippi flood plain receive layers of sediment from the river's
+overflow. The river very rarely breaks through a levee. The United
+States Government has spent great sums in walling in the river, and each
+state along its banks does its share toward paying for this
+self-protection.
+
+By means of _jetties_ the river's current is directed into a
+straightened course, and its power is expended upon the work of
+deepening its own channel and carrying its sediment to the Gulf. Much as
+the river has been forced to do in cleaning its own main channel,
+dredging is needed at various harbours to keep the river deep enough for
+navigation. The forests of the mountain slopes in Colorado are being
+slaughtered, and the headwaters of the Missouri are carrying more and
+more rocky debris to choke the current of the Mississippi. Colorado soil
+is stolen to build land in the vast delta, which is pushing out into the
+Gulf at the rate of six miles in a century--a mile in every sixteen
+years. The Mississippi delta measures 14,000 square miles. With the
+continued denuding of mountain slopes, we shall expect the rate of delta
+growth to be greatly increased, until reforesting checks the destructive
+work of wind and water.
+
+
+
+
+THE MAKING OF MOUNTAINS
+
+
+The gradual thickening and shrinking of the earth's crust as it cools
+have made the wrinkles we call mountain systems. Through millions of
+years the globe has been giving off heat to the cold sky spaces through
+which it swings in its orbit around the sun. The cooling caused the
+contraction of the outer layer to fit the shrinking of the mass. When a
+plump peach dries on its pit, the skin wrinkles down to fit the dried
+flesh. The fruit shrinks by loss of water, just as the face of an old
+person shrinks by loss of fat. The skin becomes wrinkled in both cases.
+
+The weakest places in the earth's crust were the places to crumple,
+because they could not resist the lateral pressure that was exerted by
+the shrinking process. Along the shores of the ancient seas the rivers
+piled great burdens of sediment. This caused the thin crust to sink and
+to become a basin alongside of a ridge. The wearing away of the land in
+certain places lightened and weakened the crust at these places, so that
+it bent upward in a ridge.
+
+Perhaps the first wrinkles were not very high and deep. The gradual
+cooling must have exerted continued pressure, and the wrinkles have
+become larger. It is not likely that new wrinkles would be formed as
+long as the old ones would crumple and draw up into narrower, steeper
+slopes, in response to the lateral crushing.
+
+We can imagine those first mountains rising as folds under the sea.
+Gradually their bases were narrowed, and their crests lifted out of the
+water. They rose as long, narrow islands, and grew in size as time went
+on.
+
+Why is the trend of the great mountain systems almost always north and
+south? Study the map of the continents and see how few cross ranges are
+shown, and how short they are, compared with the others. The molten
+globe bulged at its equator, as it rotated on its axis. The moon added
+its strong pulling force to make it bulge still more. As the crust
+thickened, it became less responsive to the two forces that caused it to
+bulge. The shrinkage was greatest where the globe had been most pulled
+out of shape. The rate of the earth's rotation is believed to have
+diminished. Every change tended to let the earth draw in its (imaginary)
+belt, a notch at a time. The forces of contraction acted along the line
+of the equator, and formed folds running toward the poles. In this early
+time the great mountain systems were born, and they grew in size
+gradually, from small beginnings.
+
+These mountains of upheaval, made by the bending of the earth's crust,
+and the formation of alternating ridges and depressed valleys, are many.
+The earth is old and much wrinkled. Other mountains have been formed by
+forces quite different. Volcanic mountains have been far more numerous
+in ages gone than they are now.
+
+Mt. Hood and Mt. Rainier are peaks built up by the materials thrown out
+of the craters of volcanoes dead these thousands of years. Vesuvius is
+at present showing us how volcanic mountains are made. Each eruption
+builds larger the cone--that is, the chimney through which the molten
+rocks, the ashes, and the steam are ejected. Side craters may open, the
+main cone be broken and its form changed, but the mass of lava and
+stones and ashes grows with each eruption. The mountain grows by the
+additions it receives. AEtna is a mountain built of lava.
+
+A third mountain system grew, not by addition, but by subtraction. The
+Catskills illustrate this type. This group of mountains is the remnant
+of a table-land made of level layers of red sandstone. The rest of the
+high plain has been cut down and carried away, leaving these picturesque
+hills, the survival of which is as much a mystery as the disappearance
+of the balance of the plateau of which they were once a part.
+
+The fold that forms a typical mountain ridge has a cone of granite, the
+original rock foundation of the earth, and on this are layers of
+stratified rock, ancient deposits of sediment carried to the sea by
+streams. When exposed to wind and rain, the ridge is gradually worn
+down. In some places the water cuts away the soft rock and forms a
+stream-bed, that cuts deeper and deeper, using the rock fragments as its
+tools. Often the layers of aqueous rocks are cut through, and the
+granite exposed.
+
+Sometimes the hardest stratified rock-beds resist the water and the wind
+and are left as a series of ridges along the sides of the main range.
+The crumpling forces may crack the ridge open for its whole length, and
+one side of the chasm may slip down and the other go up. The result is a
+sheer wall of exposed rock strata, layers of which correspond with those
+that lie far below the top of the portion that slid down in the great
+upheaval and subsidence that parted them. These slips are known as
+_faults_.
+
+
+
+
+THE LAVA FLOOD OF THE NORTHWEST
+
+
+We know little about the substance that occupies the four thousand miles
+of distance between the surface and the centre of our earth. We know
+that the terrible weight borne by the central mass compresses it, so
+that the interior must grow denser as the core is approached. Scientists
+have weighed the earth, and tell us that the crust is lighter than the
+rest. The supposition is that there is a great deal of iron in the
+interior, and possibly precious metals, too.
+
+Our deepest wells and mines go down about a mile, then digging stops, on
+account of the excessive heat. But the crumpling of the crust, and the
+wearing away of the folded strata by wind and running water, have laid
+bare rocks several miles in thickness on the slopes of mountains, and
+exposed the underlying granite, on which the first sedimentary rocks
+were deposited. On this granite lie stratified rocks, which are
+crystalline in texture. These are the beds, sometimes miles in depth,
+called _metamorphic_ rocks, formed by water, then transformed by heat.
+
+The wearing away of rocks by wind and water has furnished the materials
+out of which the aqueous rocks have been made. Layers upon layers of
+sandstone, shales, limestone, and the like, are exposed when a river
+cuts a canyon through a plateau. The layered deposits of debris at the
+mouth of the river make new aqueous rocks out of old. Every sandy beach
+is sandstone in the making. This work is never ended.
+
+In the early days the earth's crust often gaped open in a mighty crater
+and let a flood of lava overspread the surface. The ocean floor often
+received this flood of melted rock. In many places the same chimney
+opened again and again, each time spreading a new layer of lava on top
+of the old, so that the surface has several lava sheets overlying the
+aqueous strata.
+
+If the hardened lava sheet proved a barrier to the rising tide of molten
+lava in the chimney it was often forced out in sheets between the layers
+of aqueous rocks. Wherever the heated material came into contact with
+aqueous rocks it transformed them, for a foot or more, into crystalline,
+metamorphic rocks.
+
+A chimney of lava is called a _dike_. In mountainous countries dikes are
+common. Sometimes small, they may also be hundreds of feet across, often
+standing high above the softer strata, which rains have worn away. Dikes
+often look like ruined walls, and may be traced for miles where they
+have been overturned in the mountain-making process.
+
+The great lava flood of the Northwest happened when the Coast Range was
+born. Along the border of the Pacific Ocean vast sedimentary deposits
+had accumulated during the Cretaceous and Tertiary Periods. Then the
+mighty upheaval came, the mountain ridge rose at the end of the Miocene
+epoch and stretched itself for hundreds of miles through the region
+which is now the coast of California and Oregon. Great fissures opened
+in the folded crust, and floods of lava overspread an area of 150,000
+square miles. A dozen dead craters show to-day where those immense
+volcanic chimneys were. The depth of the lava-beds is well shown where
+the Columbia River has worn its channel through. Walls of lava three
+thousand feet in thickness rise on each side of the river. They are made
+of columns of basalt, fitted together, like cells of a honeycomb, and
+jointed, forming stone blocks laid one upon another. The lava shrinks on
+cooling and forms prisms. In Ireland, the Giants' Causeway is a famous
+example of basaltic formation. In Oregon, the walls of the Des Chutes
+River show thirty lava layers, each made of vertical basalt columns. The
+palisades of the Hudson, Mt. Tom, and Mt. Holyoke are examples on the
+eastern side of the continent of basaltic rocks made by lava floods.
+
+Northern California, northwestern Nevada, and large part of Idaho,
+Montana, Oregon, and Washington are included in the basin filled with
+lava at the time of the great overflow, which extended far into British
+Columbia. It is probable that certain chimneys continued to discharge
+until comparatively recent times. Mt. Rainier, Mt. Shasta, and Mt. Hood
+are among dead volcanoes.
+
+Quite a different history has the great Deccan lava-field of India,
+which covers a larger area than the basin of our Northwest, and is in
+places more than a mile in depth. It has no volcanoes, nor signs of any
+ever having existed. The floods alone overspread the region, which shows
+no puny "follow-up system" of scattered craters, intermittently in
+eruption.
+
+
+
+
+THE FIRST LIVING THINGS
+
+
+Strange days and nights those must have been on the earth when the great
+sea was still too hot for living things to exist in it. The land above
+the water-line was bare rocks. These were rapidly being crumbled by the
+action of the air, which was not the mild, pleasant air we know, but was
+full of destructive gases, breathed out through cracks in the thin crust
+of the earth from the heated mass below. If you stand on the edge of a
+lava lake, like one of those on the islands of the Hawaiian group, the
+stifling fumes that rise might make you feel as if you were back at the
+beginning of the earth's history, when the solid crust was just a thin
+film on an unstable sea of molten rock, and this volcano but one of the
+vast number of openings by which the boiling lava and the condensed
+gases found their way to the surface. Then the rivers ran black with the
+waste of the rocky earth they furrowed, and there was no vegetation to
+soften the bleakness of the landscape.
+
+The beginnings of life on the earth are a mystery. Nobody can guess the
+riddle. The earliest rocks were subjected to great heat. It is not
+possible that life could have existed in the heated ocean or on the
+land. Gradually the shores of the seas became filled up with sediment
+washed down by the rivers. Layer on layer of this sediment accumulated,
+and it was crumpled by pressure, and changed by heat, so that if any
+plants or animals had lived along those old shores their remains would
+have been utterly destroyed.
+
+Rocks that lie in layers on top of these oldest, fire-scarred
+foundations of the earth show the first faint traces of living things.
+Limestone and beds of iron ore are signs of the presence of life. The
+first animals and plants lived in the ancient seas.
+
+From the traces that are left, we judge that the earliest life forms
+were of the simplest kind, like some plants and animals that swim in a
+drop of water. Have you ever seen a drop of pond water under a compound
+microscope? It is a wonder world you look into, and you forget all the
+world besides. You are one of the wonderful higher animals, the highest
+on the earth. You focus on a shapeless creature that moves about and
+feels and breathes, but hasn't any eyes or mouth or stomach--in fact, it
+is the lowest form of animal life, and one of the smallest. It is but
+one of many animal forms, all simple in structure, but able to feed and
+grow and reproduce their kind.
+
+Gaze out of the window on the garden, now. The flowering plants, the
+green grass, and the trees are among the highest forms of plants. In the
+drop of water under the microscope tiny specks of green are floating.
+They belong to the lowest order of plants. Among the plant and the
+animal forms that have been studied and named, are a few living things
+the places of which in the scale are not agreed upon. Some say they are
+animals; some believe they are plants. They are like both in some
+respects. It is probable that the first living things were like these
+confusing, minute things--not distinctly plants or animals, but the
+parent forms from which, later on, both plants and animals sprang.
+
+The lowest forms of life, plant and animal, live in water to-day. They
+are tiny and their bodies are made of a soft substance like the white of
+an egg. If these are at all like the living creatures that swarmed in
+the early seas, no wonder they left no traces in the rocks of the early
+part of the age when life is first recorded by fossils. Soft-bodied
+creatures never do.
+
+Some of the animals and the plants in the drop of water under the
+microscope have body walls of definite shapes, made of lime, or of a
+glassy substance called silica. When they die, these "skeletons" lie at
+the bottom of the water, and do not decay, as the living part of the
+body does, because they are mineral. Gradually a number of these shells,
+or hard skeletons, accumulate. In a glass of pond water they are found
+at the bottom, amongst the sediment. In a pond how many thousands of
+these creatures must live and their shells fall to the bottom at last,
+buried in the mud!
+
+So it is easy to understand why the first creatures on earth left no
+trace. The first real fossils found in the rocks are the hard shells or
+skeletons of the first plants and animals that had hard parts.
+
+
+
+
+AN ANCIENT BEACH AT EBB TIDE
+
+
+When the tide is out, the rocks on the Maine coast have plenty of living
+creatures to prove this northern shore inhabited. Starfishes lurk in the
+hollows, and the tent-shaped shells of the little periwinkle encrust the
+wet rocks. Mussels cling to the rocks in clumps, fastened to each other
+by their ropes of coarse black hair. The furry coating of sea mosses
+that encrust the rocks is a hiding-place for many kinds of living
+things, some soft-bodied, some protected by shells. The shallow water is
+the home of plants and animals of many different kinds. As proof of this
+one finds dead shells and fragments of seaweeds strewn on the shore
+after a storm.
+
+Along the outer shores of the Cape Cod peninsula and down the Jersey
+coast, the sober colouring of the shells of the north gives way to a
+brighter colour scheme. In the warmer waters, life becomes gayer, if we
+may judge by the rich tints that ornament the shells. The kinds of
+living creatures change. They are larger and more abundant. The seaweeds
+are more varied and more luxuriant in growth.
+
+When we reach the shores of the West Indian islands and the keys of
+Florida the greatest abundance and variety of living forms are found.
+The submerged rocks blossom with flower-like sea anemones of every
+colour. Corals, branching like trees and bushes on the sea floor, form
+groves under water. Among them brilliant-hued fishes swim, and highly
+ornamented shells glide, as people know who have gazed through the glass
+bottoms of the boats built especially to show visitors the wonderful sea
+gardens at Nassau, Bahama Islands, and at Santa Catalina Island,
+southern California.
+
+On every beach the skeletons of animals which die help to build up the
+land; though the process is not so rapid in the north as on the shores
+that approach the tropics. The coast of Florida has a rim of island
+reefs around it built out of coral limestone. Indeed, the peninsula was
+built by coral polyps. Houses in St. Augustine are built of coquina
+rock, which is simply a mass of broken shells held together by a lime
+cement. Every sea beach is packed with shells and other remnants of
+animals and plants that live in the shallow waters. Deeper and deeper
+year by year the sand buries these skeletons, and many of them are
+preserved for all time.
+
+Thus what is sandy beach to-day may, a few million years from now, be
+uncovered as a ledge of sandstone with the prints of waves distinctly
+shown, and fossil shells of molluscs, skeletons of fishes, and branches
+of seaweed--all of them different from those then growing upon the
+earth.
+
+In the neighbourhood of Cincinnati there have been uncovered banks of
+stone accumulated along the border of an ancient sea. From the sides of
+granite highlands streams brought down the sand built into these oldest
+sandstone rocks. The fine mud which now appears as beds of slate was the
+decay of feldspar and hornblende in the same granite. Limestone beds are
+full of the fossil shells of creatures that lived in the shallow seas.
+Their skeletons, accumulating on the bottom, formed deep layers of
+limestone mud. These rocks preserve, by the fossils they contain, a
+great variety of shellfish which had limy skeletons. The sea fairly
+swarmed along its shallow margin with these creatures. We might not
+recognize many of the shells and other curious fossils we find in the
+rock uncovered by the workmen who are cutting a railroad embankment.
+They are not exactly like the living forms that grow along our beaches
+to-day, but they are enough like them for us to know that they lived
+along the seashore, and if we had time to examine all the rocks of this
+kind preserved in a museum we should decide that seashore life was quite
+as abundant then as it is now. The pressed specimens of plants of those
+earliest seashores are mere imprints showing that they were pulpy and
+therefore gradually decayed. Only their shape is recorded by dark stains
+made by each branching part. The decay of the vegetable tissue painted
+the outline on the rock which when split apart shows us what those
+ancient seaweeds looked like. They belonged to the group of plants we
+call kelp, or tangle, which are still common enough in the sea, though
+the forms we now have are not exactly like the old ones. Seaweeds belong
+to the very lowest forms of plants.
+
+[Illustration: Crinoid from Indiana]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Ammonite from Jurassic of England]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Fossil corals Coquina, Hippurite limestone]
+
+The limestones are full of fossils of corals. Indeed, there must have
+been reefs like those that skirt Florida to-day built by these
+lime-building polyps. Their forms are so well preserved in the rocks
+that it is possible to know just how they looked when they grew in the
+shallows.
+
+One very common kind is called a cup coral, because the polyp formed a
+skeleton shaped like a cup. The body wall surrounded the skeleton, and
+the arms or tentacles rose from the centre of the funnel-like depression
+in the top. Little cups budded off from their parents, but remained
+attached, and at length the skeletons of all formed great masses of limy
+rock. Some cup corals grew in a solid mass, the new generation forming
+an outer layer, thus burying the parent cups.
+
+A second type of corals in these oldest limestones is the honeycomb
+group. The colonies of polyps lived in tubes which lengthened gradually,
+forming compact, limy cylinders like organ pipes, fitted close together.
+The living generation always inhabited the upper chambers of the tubes.
+A third type is the chain coral, made of tubes joined in rows, single
+file like pickets of a fence. But these walls bend into curious
+patterns, so that the cross-section of a mass of them looks like a
+complex pattern of crochet-work, the irregular spaces fenced with chain
+stitches. Each open link is a pit in which a polyp lived.
+
+Among the corals are sprays of a fine feathery growth embedded in the
+limestone. Fine, straight, splinter-like branches are saw-toothed on one
+or both edges. These limy fossils might not be seen at all, were they
+not bedded in shales, which are very fine-grained. Here again are the
+skeletons of animals. Each notch on each thread-like branch was the home
+of a tiny animal, not unlike a sea anemone and a coral polyp.
+
+To believe this story it is necessary only to pick up a bit of dead
+shell or floating driftwood on which a feathery growth is found. These
+plumes, like "sea mosses," as they are called, are not plants at all,
+but colonies of polyps. Each one lived in a tiny pit, and these pits
+range one above the other, so as to look like notches on the thread-like
+divisions of the stem. Put a piece of this so-called "sea moss" in a
+glass of sea water, and in a few moments of quiet you will see, by the
+use of a magnifying glass, the spreading arms of the polyp thrust out of
+each pit.
+
+The ancient seas swarmed with these living hydrozoans, and their remains
+are found preserved as fossils in the shales which once were beds of
+soft mud.
+
+The hard shells of sea urchins and starfishes are made of lime. In the
+ancient seas, starfishes were rare and sea urchins did not exist, but
+all over the sea bottom grew creatures called crinoids, the soft parts
+of which were enclosed in limy protective cases and attached to rocks on
+the sea bottom by means of jointed stems. No fossils are more plentiful
+in the early limestones than these wonderful "stone lilies." Indeed, the
+crinoidal limestone seemed to be built of the skeletons of these
+animals. The lily-like body was flung open, as a lily opens its calyx,
+when the creature was feeding. But any alarm caused the tentacles to be
+drawn in, and the petal-like divisions of the body wall to close tightly
+together, till that wall looked like an unopened bud.
+
+On the bottom of the Atlantic, near the Bahama Islands, these stone
+lilies are still found growing. Their jointed stems and body parts are
+as graceful in form and motion as any lily. The creature's mouth is in
+the centre of the flower-like top, and it feeds like the sea urchin, on
+particles obtained in the sea water.
+
+The old limestones contain great quantities of "lamp shells," which are
+old-fashioned bivalves. Their shells remind us of our bivalve clams and
+scallops, but the internal parts were very different. The gills of clams
+and oysters are soft parts. Inside of the lamp shells are coiled, bony
+arms, supporting the fringed gills.
+
+It is fortunate for us that a few lamp shells still live in the seas. By
+studying the soft parts of these living remnants of a very old race we
+can know the secrets of the lives of those ancient lamp shells, the
+soft parts of which were all washed away, and the fossil shells of which
+are preserved. Gradually the lamp shells died out, and the modern
+bivalves have come to take their places. Just so, the ancient crinoids
+are now almost extinct; the sea urchins and the starfishes have
+succeeded them.
+
+The chambered nautilus has its shell divided by partitions and it lives
+in the outer chamber, a many-tentacled creature, that is a close
+relative of the soft-bodied squid. In the ancient seas the same family
+was represented by huge creatures the shells of which were chambered,
+but not coiled. Their abundance and great size are proved by the rocks
+in which their fossils are preserved. Some of them must have been the
+rulers of the sea, as sharks and whales are to-day. Fossil specimens
+have been found more than fifteen feet long and ten inches in diameter
+in the ancient rocks of some of the Western States. It is possible to
+read from the lowest rock formations upward, the rise of these sea
+giants and their gradual decline. Certain strata of limestone contain
+the last relics of this race, after which they became extinct. As the
+straight-chambered forms diminished, great coiled forms became more
+abundant, but all died out.
+
+One of the most abundant fossil animals in ancient rocks is called a
+trilobite. Its body is divided by two grooves into three parts, a
+central ridge extending the whole length of the body and two side
+ridges. The front portion of the shell formed the head shield, and
+behind the main body part was a little tail shield. The skeleton was
+formed of many movable jointed plates, and the creature had eyes set in
+the head shield just as the king crab's are set. Jointed legs in pairs
+fringed each side of the body. Each leg had two branches, one for
+walking, the other for swimming. A pair of feelers rose from the head.
+The body could be rolled into a ball when danger threatened, by bringing
+head and tail together.
+
+These remarkable, extinct trilobites were the first crustaceans. Their
+nearest living relative to-day is the horseshoe crab. The fresh-water
+crayfish and the lobster are more distant relatives: so are the shrimps
+and the prawns. No such abundance of these creatures exists to-day as
+existed when the trilobites thronged the shallows. So well preserved are
+these skeletons that, although there are no living trilobites for
+comparison, it is possible to find out from the fossil enough about
+their structure to know how they fed and lived their lives along with
+the straight-horns which were the scavengers of those early seas and the
+terror of smaller creatures. The trilobites throve, and, dying, left
+their record in the rocks; then disappeared entirely. We find their
+fossils in a great variety of forms, shapes, and sizes. The smallest is
+but a fraction of an inch long, the largest twenty inches long.
+
+The ancient rocks, in which these lower forms of life have left their
+fossils, are known as the Silurian system. The time in which these rocks
+were accumulating under the seas covers a vast period. We call it the
+Age of Invertebrates, because these soft-bodied, hard-shelled animals,
+the crinoids, the molluscs, and the trilobites, with bony external
+skeletons and no backbones, were the most abundant. They overshadowed
+all other forms of life. The rocks of this wonderful series were formed
+on the shores of a great inland sea that covered the central portion of
+North America. In the ages that followed, these rocks were covered
+deeply with later sediments. But the upheavals of the crust have broken
+open and erosion has uncovered these strata in different regions.
+Geologists have found written there, page upon page, the record of life
+as it existed in the early seas.
+
+
+
+
+THE LIME ROCKS
+
+
+"Hard" water and "soft" water are very different. The rain that falls
+and fills our cisterns is not softer or more delightful to use than the
+well water in some favoured regions. In it, soap makes beautiful, creamy
+suds, and it is a real pleasure to put one's hands into it. But in hard
+water soap seems to curdle, and some softening agent like borax has to
+be added or the water will chap the hands. There is little satisfaction
+in using water of this kind for any purpose.
+
+Hard water was as soft as any when it fell from the sky; but the rain
+water trickled into the ground and passed through rocks containing lime.
+Some of this mineral was absorbed, for lime is readily soluble in water.
+Clear though it may be, water that has lime in it has quite a different
+feeling from rain water. Blow the breath into a basin of hard water, and
+a milky appearance will be noted. The carbonic acid gas exhaled from the
+lungs unites with the invisible lime, causing it to become visible
+particles of carbonate of lime, which fall to the bottom of the basin.
+
+Nearly all well water is hard. So is the water of lakes and rivers and
+the ocean, for limestone is one of the most widely distributed rocks in
+the surface of the earth. Rain water makes its way into the earth's
+crust, absorbs mineral substances, and collects in springs which feed
+brooks and rivers and lakes. Wells are holes in the ground which bore
+into water-soaked strata of sand.
+
+We gain something from the lime dissolved in hard water, for it is an
+essential part of our food. We must drink a certain amount of water each
+day to keep the body in perfect health. The lime in this water goes
+chiefly to the building of our bones. Plant roots take up lime in the
+water that mounts as sap through the plant bodies. We get some of the
+lime we need in vegetable foods we eat.
+
+All of the kingdom of vertebrate animals, from the lowest forms to the
+highest, all of the shell-bearing animals of sea and land, require lime.
+Many of the lower creatures especially these in the sea, such as corals
+and their near relatives, encase themselves in body walls of lime. They
+absorb the lime from the sea water, and deposit it as unconsciously as
+we build the bony framework of our bodies.
+
+All the bone and shell-bearing creatures that die on the earth and in
+the sea restore to the land and to the water the lime taken by the
+creatures while they lived. Carbonic acid gas in the water greatly
+hastens the dissolving of dead shells. Carbonic acid gas, whether free
+in the air, or absorbed by percolating water, hastens the dissolving of
+skeletons of creatures that die upon land. Then the raw materials are
+built again into lime rocks underground.
+
+The lime rocks are the most important group in the list of rocks that
+form the crust of the earth. They are made of the elements calcium,
+carbon, and oxygen, yet the different members of this calcite group
+differ widely in composition and appearance. So do oyster shells and
+beef bones, though both contain quantities of carbonate of lime.
+
+Calcite is a soft mineral, light in weight, sometimes white, but oftener
+of some other colour. It may be found crystallized or not. Whenever a
+drop of acid touches it, a frothy effervescence occurs. The drop of acid
+boils up and gives off the pungent odour of carbonic acid gas.
+
+The reason that calcite is hard to find in rocks is that percolating
+water, charged with acids, is constantly stealing it, and carrying it
+away into the ocean. The rocks that contain it crumble because the limy
+portions have been dissolved out.
+
+Some limestones resist the destructive action of water. When they are
+impregnated with silica they become transformed into marble, which takes
+a high polish like granite. Acids must be strong to make any impression
+on marble.
+
+The thick beds of pure limestone that underlie the surface soil in
+Kentucky and in parts of Virginia sometimes measure several hundred feet
+in thickness, a single stratum often being twenty feet thick. They are
+all horizontal, for they were formed on sea bottom, and have not been
+crumpled in later time. The dead bodies of sea creatures contributed
+their shells and skeletons to the lime deposit on the sea bottom. Who
+can estimate the time it took to form those thick, solid layers of lime
+rock? The animals were corals, crinoids, and molluscs. Little sand and
+clay show in the lime rock of this period, before the marshes of the
+Carboniferous Age took the place of the ancient inland sea of the
+Subcarboniferous Period, the sedimentary accumulations of which we are
+now talking about.
+
+The living corals one sees in the shallow water of the Florida coast
+to-day are building land by building up their limy skeletons. The reefs
+are the dead skeletons of past generations of these tiny living things.
+They take in lime from the water, and use it as we use lime in building
+our bones. In each case it is an unconscious process of animal
+growth--not a "building process" like a mason's building of a wall. Many
+people think that the coral polyp builds in this way. They give it
+credit for patience in a great undertaking. All the polyp does is to
+feed on whatever the water supplies that its digestive organs can use.
+It is like a sea anemone in appearance and in habits of life. It is not
+at all like an insect. Yet it is common to hear people speak of the
+"coral insect"! Do not let any one ever hear you repeat such a mistake.
+
+Southern Florida is made out of coral rock, but thinly covered with
+soil. It was made by the growth of reef after reef, and it is still
+growing.
+
+The Cretaceous Period of the earth's eventful history is named for the
+lime rock which we know as chalk. Beds of this recent kind of limestone
+are found in England and in France, pure white, made of the skeletons of
+the smallest of lime-consuming creatures, Foraminifera. They swarmed in
+deep water, and so did minute sponge animalcules and plant forms called
+Diatoms that took silica from the water, and formed their hard parts of
+this glassy substance. The result is seen in the nodules of flint found
+in the soft, snow-white chalk. Did you ever use a piece of chalk that
+scratched the black-board? The flint did it. Have you ever seen the
+chalk cliffs of Dover? When you do see them, notice how they gleam white
+in the sun. See how the rains have sculptured those cliffs. The
+prominences left standing out are strengthened by the flint they
+contain. Chalk beds occur in Texas and under our great plains; but the
+principal rocks of the age in America were sandstones and clays.
+
+
+
+
+THE AGE OF FISHES
+
+
+The first animal with a backbone recorded its existence among the
+fossils found in rocks of the upper Silurian strata. It is a fish; but
+the earliest fossils are very incomplete specimens. We know that these
+old-fashioned fishes were somewhat like the sturgeons of our rivers.
+Their bodies were encased in bony armour of hard scales, coated with
+enamel. The bones of the spine were connected by ball and socket joints,
+and the heads were movable. In these two particulars the fishes
+resembled reptiles. The modern gar-pike has a number of the same
+characteristics.
+
+Another backboned creature of the ancient seas was the ancestral type of
+the shark family. In some points this old-fashioned shark reminds us of
+birds and turtles. These early fishes foreshadowed all later
+vertebrates, not yet on the earth. After them came the amphibians, then
+the reptiles, then the birds, and latest the mammals.
+
+The race of fishes began, no doubt, with forms so soft-boned that no
+fossil traces are preserved in the rocks. When those with harder bones
+appeared, the fossil record began, and it tells the story of the passing
+of the early, unfish-like forms, and the coming of new kinds, great in
+size and in numbers, that swarmed in the seas, and were tyrants over all
+other living things. They conquered the giant straight-horns and
+trilobites, former rulers of the seas.
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+A sixteen-foot fossil fish from Cretaceous of Kansas, with a modern
+tarpon]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Canon Diablo meteorite from Arizona]
+
+One of these giant fishes fifteen to twenty feet long, three feet wide,
+had jaws two feet long, set with blade-like teeth. Devonian rocks in
+Ohio have yielded fine fossils of gigantic fishes and sharks.
+
+Devonian fishes were unlike modern kinds in these particulars, the
+spinal column extended to the end of the tail, whether the fins were
+arranged equally or unequally on the sides; the paired side fins look
+like limbs fringed with fins. Every Devonian fish of the gar type seems
+to have had a lung to help out its gill-breathing.
+
+In these traits the first fishes were much like the amphibians. They
+were the parent stock from which branched later the true fishes and the
+amphibians, as a single trunk parts into two main boughs. The trunk is
+the connecting link.
+
+The sea bottom was still thronged with crinoids, and lamp shells, and
+cup corals. Shells of both clam and snail shapes are plentiful. The
+chambered straight-horns are fewer and smaller, and coiled forms of this
+type of shell are found. Trilobite forms are smaller, and their numbers
+decrease.
+
+The first land plants appeared during this age. Ferns and giant club
+mosses and cycads grew in swampy ground. This was the beginning of the
+wonderful fern forests that marked the next age, when coal was formed.
+
+The rocks that bear the record of these living things in their fossils,
+form strata of great thickness that overlie the Silurian deposits. There
+is no break between them. So we understand that the sea changed its
+shore-line only when the Silurian deposits rose to the water-level.
+
+The Devonian sea was smaller than the Silurian. A great tract of
+Devonian deposits occupies the lower half of the state of New York,
+Canada between Lakes Erie and Huron, and the northern portions of
+Indiana and Illinois. These older layers of the stratified rock are
+covered with the deposits of later periods. Rivers that cut deep
+channels reveal the earlier rocks as outcrops along their canyon walk.
+The record of the age of fishes is, for the most part, still an unopened
+book. The pages are sealed, waiting for the geologist with his hammer to
+disclose the mysteries.
+
+
+
+
+KING COAL
+
+
+In this country, and in this age, who can doubt that coal is king? It is
+one of the few necessities of life. In various sections of the country,
+layers of coal have been discovered--some near the surface, others deep
+underground. These are the storehouses of fuel which the coal miners dig
+out and bring to the surface, and the railroads distribute. From
+Pennsylvania and Ohio to Alabama stretches the richest coal-basin.
+Illinois and Indiana contain another. From Iowa southward to Texas
+another broad basin lies. Central Michigan and Nova Scotia each has
+isolated coal-basins. All these have been discovered and mined, for they
+lie in the oldest part of the country.
+
+In the West, coal-beds have been discovered in several states, but many
+regions have not yet been explored. Vast coal-fields, still untouched,
+have been located in Alaska. The Government is trying to save this fuel
+supply for coming generations. Many of the richest coal-beds from Nova
+Scotia southward dip under the ocean. They have been robbed by the
+erosive action of waves and running water. Glaciers have ground away
+their substance, and given it to the sea. Much that remains intact must
+be left by miners on account of the difficulties of getting out coal
+from tilted and contorted strata.
+
+As a rule, the first-formed coal is the best. The Western coal-fields
+belong to the period following the Carboniferous Age. Although
+conditions were favourable to abundant coal formation, Western coal is
+not equal to the older, Eastern coal. It is often called _lignite_, a
+word that designates its immaturity compared with anthracite.
+
+Coal formed in the Triassic Period is found in a basin near Richmond,
+Virginia. There is an abundance of this coal, but it has been subjected
+to mountain-making pressure and heat, and is extremely inflammable. The
+miners are in constant danger on account of coal gas, which becomes
+explosive when the air of the shaft reaches and mingles with it. This
+the miner calls "fire damp." North Carolina has coal of the same
+formation, that is also dangerous to mine, and very awkward to reach, on
+account of the crumpling of the strata.
+
+There are beds of coal so pure that very little ash remains after the
+burning. Five per cent, of ash may be reasonably expected in pure coal,
+unmixed with sedimentary deposits. Such coal was formed in that part of
+the swamp which was not stirred by the inflow of a river. Wherever muddy
+water flowed in among the fallen stems of plants, or sand drifted over
+the accumulated peat, these deposits remained, to appear later and
+bother those who attempt to burn the coal.
+
+[Illustration: Eocene fish]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Trilobite from the Niagara limestone, Upper Silurian, of Western New
+York]
+
+[Illustration: Sigillaria, Stigmaria and Lepidodendron]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Coal fern]
+
+You know pure coal, that burns with great heat and leaves but little
+ashes. You know also the other kind, that ignites with difficulty, burns
+with little flame, gives out little heat, and dying leaves the furnace
+full of ashes. You are trying to burn ancient mud that has but a small
+proportion of coal mixed with it. The miners know good coal from poor,
+and so do the coal dealers. It is not profitable to mine the impure part
+of the vein. It costs as much to mine and ship as the best quality, and
+it brings a much lower price.
+
+The deeper beds of coal are better than those formed in comparatively
+recent time and found lying nearer the surface. In many bogs a layer of
+embedded root fibres, called peat, is cut into bricks and dried for
+burning. Deeper than peat-beds lie the _lignites_, which are old beds of
+peat, on the way to become coal. _Soft coal_ is older than lignite. It
+contains thirty to fifty per cent. of volatile matter, and burns
+readily, with a bright blaze. The richest of this bituminous coal is
+called _fat_, or _fusing coal_. The bitumen oozes out, and the coal
+cakes in burning. Ordinary soft coal contains less, but still we can see
+the resinous bitumen frying out of it as it burns. There is more heat
+and less volatile matter in _steam coal_, so-called because it is the
+fuel that most quickly forms steam in an engine. _Hard coal_ contains
+but five to ten per cent. of volatile matter. It is slow to ignite and
+burns with a small blue blaze.
+
+From peat to anthracite coal I have named the series which increases
+gradually in the amount of heat it gives out, and increases and then
+decreases in its readiness to burn and in the brightness of its flame.
+Anthracite coal has the highest amount of fixed carbon. This is the
+reason why it makes the best fuel, for fixed carbon is the substance
+which holds the store of imprisoned sunlight, liberated as heat when the
+coal burns. Tremendous pressure and heat due to shrinking of the earth's
+crust have crumpled and twisted the strata containing coal in eastern
+Pennsylvania, and thus changed bituminous coal into anthracite. Ohio
+beds, formed at the same time, but undisturbed by heat and pressure, are
+bituminous yet.
+
+The coal-beds of Rhode Island are anthracite, but the coal is so hard
+that it will not burn in an open fire. The terrible, mountain-making
+forces that crumpled these strata and robbed the coal of its volatile
+matter, left so little of the gas-forming element, that a very special
+treatment is necessary to make the carbon burn. It is used successfully
+in furnaces built for the smelting of ores.
+
+The last stage in the coal series is a black substance which we know as
+black lead, or graphite. We write with it when we use a "lead" pencil.
+This is anthracite coal after all of the volatile matter has been driven
+out of it. It cannot burn, although it is solid carbon. The beds of
+graphite have been formed out of coal by the same changes in the
+earth's crust which have converted soft coal into anthracite.
+
+The tremendous pressure that bears on the coal measures has changed a
+part of the carbon into liquid and gaseous form. Lakes of oil have been
+tapped from which jets of great force have spouted out. Such
+accumulations of oil usually fill porous layers of sandstone and are
+confined by overlying and underlying beds of impervious clay. Gas may be
+similarly confined until a well is drilled, relieving the pressure, and
+furnishing abundant or scanty supply of this valuable fuel. Western
+Pennsylvania coal-fields have beds of gas and oil. If mountain-making
+forces had broken the strata, as in eastern Pennsylvania, the gas and
+the oil would have been lost by evaporation.
+
+This is what happened in the anthracite coal-belt.
+
+
+
+
+HOW COAL WAS MADE
+
+
+The broad, rounded dome of a maple tree shades my windows from the
+intense heat of this August day. The air is hot, and every leaf of the
+tree's thatched roof is spread to catch the sunlight. The carbon in the
+air is breathed in through openings on the under side of each leaf. The
+sap in the leaf pulp uses the carbon in making starch. The sun's heat is
+absorbed. It is the energy that enables the leaf-green to produce a
+wonderful chemical change. Out of soil water, brought up from the roots,
+and the carbonic acid gas, taken in from the air, rich, sugary starch is
+manufactured in the leaf laboratory.
+
+This plant food returns in a slow current, feeding the growing cells
+under the bark, from leaf tip to root tip, throughout the growing tree.
+The sap builds solid wood. The maple tree has been built out of muddy
+water and carbon gas. It stands a miracle before our eyes. In its tough
+wood fibres is locked up all the heat its leaves absorbed from the sun,
+since the day the maple seed sprouted and the first pair of leaves
+lifted their palms above the ground.
+
+If my maple tree should die, and fall, and lie undisturbed on the
+ground, it would slowly decay. The carbon of its solid frame would pass
+back into the air, as gas, and the heat would escape so gradually that I
+could not notice it at all, unless I thrust my hand into the warm,
+crumbling mass.
+
+If my tree should be cut down to-day and chopped into stove wood, it
+would keep a fire in my grate for many months.
+
+Burning destroys wood substance a great deal faster than decay in the
+open air does, but the processes of rotting and burning are alike in
+this: each process releases the carbon, and gives it back to the air. It
+gives back also the sun's heat, stored while the tree was growing. There
+is left on the ground, and in the ashes on the hearth, only the mineral
+substance taken up in the water the roots gathered underground.
+
+If my tree stood in swampy ground and fell over under a high wind, the
+water that covered it and saturated its substance would prevent decay.
+The carbon would not be allowed to escape as a gas to the air; the woody
+substance would become gradually changed into _peat_. In this form it
+might remain for thousands of years, and finally be changed into coal.
+
+Whether it was burned while yet in the condition of peat, or millions of
+years later, when it was transformed into coal, the heat stored in its
+substance was liberated by the burning. The carbon and the heat went
+back to the air.
+
+Every green plant we see spreads its leaves to the sun. Every stick of
+wood we burn, and every lump of coal, is giving back, in the form of
+light and heat, the energy that came from sunshine and was captured by
+the green leaves. How long the wood has held this store of heat we may
+easily compute, for we can read the age of a tree. But the age of coal
+we cannot accurately state. The years probably should be counted by
+millions, instead of thousands.
+
+The great inland sea that covered the middle portion of the continent
+during the Silurian and the Devonian periods, became shallow by the
+deposit of vast quantities of sediment. Along the lines of the deposits
+of greatest thickness, a crumpling of the earth's crust lifted the first
+fold of the Alleghany Mountains as a great sea wall on the east, and on
+the western shore another formed the beginning of the Ozark Mountain
+system in Missouri. An island was lifted out of the sea, forming the
+elevated ground on which the city of Cincinnati now stands. Various
+other ridges and islands divided the ancient sea into much smaller
+bodies of water. Hemmed in by land these shallow sea-basins gradually
+changed into fresh-water lakes, for they no longer had connection with
+the ocean, and all the water they received came from rain. After
+centuries of freshets, and of filling in with the rock debris brought by
+the streams, they became great marshes, in which grew water-loving
+plants. Generation after generation of these plants died, and their
+remains, submerged by the water, were converted into peat. In the
+course of ages this peat became coal. This is the history of the coal
+measures.
+
+There is no guesswork here. The stems of plants do not lose their
+microscopic structure in all the ages it has taken to transform them to
+coal. A thin section of coal shows under a magnifier the structure of
+the stems of the coal-forming plants. Moreover, the veins of coal
+preserve above or below them, in shales that were once deposits of mud,
+the branching trunks of trees, perfectly fossilized. There are no better
+proofs of the vegetable origin of coal than the lumps themselves. But
+they are plain to the naked eye, while the coal tells its story to the
+man with the microscope.
+
+The fossil remains of the plants that flourished when coal was forming
+are gigantic, compared with plants of the same families now living. We
+must conclude that the climate was tropical, the air very heavy with
+moisture, and charged much more heavily than it is now with carbonic
+acid gas.
+
+These conditions produced, in rapid succession, forests of tree ferns
+and horsetails and giant club mosses. These are the three types of
+plants out of which the coal was made. They were all rich in resin,
+which makes the coal burn readily. The ferns had stems as large as tree
+trunks. Some have been found that are eighteen inches in diameter. We
+know they are ferns, because the leaves are found with their fruits
+attached to them in the manner of present-day ferns. The stems show the
+well known scar by which fern leaves are joined. And the wood of these
+fossil fern stems is tubular in structure, just as the wood of living
+ferns is to-day.
+
+Among the ferns which dominated these old marsh forests grew one kind,
+the scaly leaves of which covered the stems and bore their fruits on the
+branching tips. These giants, some of them with trunks four feet in
+diameter, belong to the same group of plants as our creeping club
+mosses, but in the ancient days they stood up among the other ferns as
+trees forty or fifty feet high.
+
+The giant scouring rushes, or horsetails, had the same general
+characteristics as the little reed-like plants we know by those names
+to-day.
+
+The highest plants of the coal period were leafy trees with nut-like
+fruits, that resemble the yew trees of the present. These gigantic trees
+were the first conifers upon the earth. They foreshadowed the pines and
+the other cone-bearing evergreens. Their leaves were broad and their
+fruits nut-like. The Japanese ginkgo, or maidenhair fern tree, is an
+old-fashioned conifer somewhat like those first examples of this family.
+Trunks sixty to seventy feet long, crowned with broad leaves and a spike
+of fruit, have been found lying in the upper layers of the coal-seams,
+and in sandstone strata that lie between the strata of coal. Peculiar
+circular discs, which the microscope reveals along the sides of the wood
+fibres of these fossil trees, prove the wood structure to be like that
+of modern conifers.
+
+Generation after generation of forests lived and died in the vast
+spreading swamps of this era. The land sank, and freshets came here and
+there, drowning out all plant life, and covering the layers of peat with
+beds of sand or mud. When the water went down, other forests took
+possession, and a new coal-bed was started. It is plainly seen that
+flooding often put an end to coal formation. Fifteen seams of coal, one
+above another, is the greatest number that have been found. The veins
+vary from one inch to forty feet in thickness. These are separated by
+layers of sandstone or shale, which accumulated as sediment, covering
+the stumps of dead tree ferns and other growths, and preserving them as
+fossils to tell the story of those bygone ages as plainly as any other
+record could have done.
+
+Fresh-water animals succeeded those of salt water in the swamps that
+formed the coal measures. Overhead, the first insects flitted among the
+branches of the tree ferns. Dragon-flies darted above the surface and
+dipped in water as they do to-day. Spiders, scorpions, and cockroaches,
+all air-breathing insects, were represented, but none of the higher,
+nectar-loving insects, like flies and bees and butterflies, were there.
+Flowering plants had not yet appeared on the earth. Snakelike
+amphibians, some fishlike, some lizard-like, and huge crocodilian forms
+appeared for the first time. These air-breathing swamp-dwellers could
+not have lived in salt water.
+
+Fresh-water molluscs and land shells appear for the first time as
+fossils in the rocks of the coal measures. On the shores of the ocean,
+the rocks of this period show that trilobites, horseshoe crabs, and
+fishes still lived in vast numbers, and corals continued to form
+limestone. The old types of marine animals changed gradually, but the
+coal measures show strikingly different fossils. These rocks bear the
+first record of fresh-water and land animals.
+
+
+
+
+THE MOST USEFUL METAL
+
+
+It is fortunate for us all that, out of the half-dozen so-called useful
+metals, iron, which is the most useful of them all to the human race,
+should be also the most plentiful and the cheapest. Aluminum is abundant
+in the common clay and soil under our feet. But separating it is still
+an expensive process; so that this metal is not commercially so
+plentiful as iron is, nor is it cheap.
+
+All we know of the earth's substance is based on studies of the
+superficial part of its crust, a mere film compared with the eight
+thousand miles of its diameter. Nobody knows what the core of the
+earth--the great globe under this surface film--is made of; but we know
+that it is of heavier material than the surface layer; and geologists
+believe that iron is an important element in the central mass of the
+globe.
+
+One thing that makes this guess seem reasonable is the great abundance
+of iron in the earth's crust. Another thing is that meteors which fall
+on the earth out of the sky prove to be chiefly composed of iron. All of
+their other elements are ones which are found in our own rocks. If we
+believe that the earth itself is a fragment of the sun, thrown off in a
+heated condition and cooling as it flew through space, we may consider
+it a giant meteor, made of the substances we find in the chance meteor
+that strikes the earth.
+
+Iron is found, not only in the soil, but in all plant and animal bodies
+that take their food from the soil. The red colour in fruits and
+flowers, and in the blood of the higher animals, is a form in which iron
+is familiar to us. It does more, perhaps, to make the world beautiful
+than any other mineral element known.
+
+But long before these benefits were understood, iron was the backbone of
+civilization. It is so to-day. Iron, transformed by a simple process
+into steel, sustains the commercial supremacy of the great civilized
+nations of the world. The railroad train, the steel-armoured battleship,
+the great bridge, the towering sky-scraper, the keen-edged tool, the
+delicate mechanism of watches and a thousand other scientific
+instruments--all these things are possible to-day because iron was
+discovered and has been put to use.
+
+It was probably one of the cave men, poking about in his fire among the
+rocks, who discovered a lump of molten metal which the heat had
+separated from the rest of the rocks. He examined this "clinker" after
+it cooled, and it interested him. It was a new discovery. It may have
+been he, or possibly his descendants, who learned that this metal could
+be pounded into other shapes, and freed by pounding from the pebbles
+and other impurities that clung to it when it cooled. The relics of
+iron-tipped spears and arrows show the skill and ingenuity of our early
+ancestors in making use of iron as a means of killing their prey. The
+earliest remains of this kind have probably been lost because the iron
+rusted away.
+
+Man was pretty well along on the road to civilization before he learned
+where iron could be found in beds, and how it could be purified for his
+use. We now know that certain very minute plants, which live in quiet
+water, cause iron brought into that water to be precipitated, and to
+accumulate in the bottom of these boggy pools. In ancient days these bog
+deposits of iron often alternated with coal layers. Millions of years
+have passed since these two useful substances were laid down. To-day the
+coal is dug, along with the bog iron. The coal is burned to melt the
+iron ore and prepare it for use. It is a fortunate region that produces
+both coal and iron.
+
+Bituminous coal is plentiful, and scattered all over the country, while
+anthracite is scarce. The cheapest iron is made in Alabama, which has
+its ore in rich deposits in hillsides, and coal measures close by,
+furnishing the raw material for coke. The result is that the region of
+Birmingham has become the centre of great wealth through the development
+of iron and coal mines.
+
+Where water flows over limestone rock, and percolates through layers of
+this very common mineral, it causes the iron, gathered in these rock
+masses, to be deposited in pockets. All along the Appalachian Mountains
+the iron has been gathered in beds which are being mined. These beds of
+ore are usually mixed with clay and other earthy substances from which
+the metal can be separated only by melting. The ore is thrown into a
+furnace where the metal melts and trickles down, leaving behind the
+non-metallic impurities. It is drawn off and run into moulds, where it
+cools in the form of "pig" iron.
+
+The first fuel used in the making of pig iron from the ore was charcoal.
+In America the early settlers had no difficulty in finding plenty of
+wood. Indeed, the forests were weeds that had to be cut down and burned
+to make room for fields of grain. The finding of iron ore always started
+a small industry in a colony. If there was a blacksmith, or any one else
+among the small company who understood working in iron, he was put in
+charge.
+
+To make the charcoal, wood was cut and piled closely in a dome-shaped
+heap, which was tightly covered with sods, except for a small opening
+near the ground. In this a fire was built, and smothered, but kept going
+until all the wood within the oven was charred.
+
+This fuel burned readily, with an intense heat, and without ashes.
+Sticks of charcoal have the form of the wood, and they are stiff enough
+to hold up the ore of iron so that it cannot crush out the fire. For a
+long time American iron was supplied by little smelters, scattered here
+and there. The workmen beat the melted metal on the forge, freeing it
+from impurities, and shaping the pure metal into useful articles.
+Sometimes they made it into steel, by a process learned in the Old
+World.
+
+The American iron industry, which now is one of the greatest in the
+world, centres in Pittsburg, near which great deposits of iron and coal
+lie close together. The making of coke from coal has replaced the
+burning of charcoal for fuel. When the forests were cut away by
+lumbermen, the supply of charcoal threatened to give out, and
+experiments were made in charring coal, which resulted in the successful
+making of coke, a fuel made from coal by a process similar to the making
+of charcoal from wood. The story of the making of coke out of hard and
+soft coal is a long one, for it began as far back as the beginning of
+the nineteenth century.
+
+In 1812 the first boat-load of anthracite coal was sent to Philadelphia
+from a little settlement along the Lehigh River. A mine had been opened,
+the owner of which believed that the black, shiny "rocks" would burn.
+His neighbours laughed at him, for they had tried building fires with
+them, and concluded that it could not be done. In Philadelphia, the
+owners of some coke furnaces gave the new fuel a trial, in spite of the
+disgust of the stokers, who thought they were putting out their fires
+with a pile of stones. After a little, however, the new fuel began to
+burn with the peculiar pale flame and intense heat that we know so
+well, and the stokers were convinced that here was a new fuel, with
+possibilities in it.
+
+But it was hard for people to be patient with the slow starting of this
+hard coal. Not until 1840 did it come into general favour, following the
+discovery that if hot air was supplied at the draught, instead of cold,
+anthracite coal became a perfect fuel.
+
+At Connellsville, Pennsylvania, a vein of coal was discovered which made
+coke of the very finest quality. Around this remarkable centre, coke
+ovens were built, and iron ore was shipped in, even from the rich beds
+of the Lake Superior country. But it was plain to see that Connellsville
+coal would become exhausted; and so experiments in coke-making from
+other coals were still made. When soft coal burns, a waxy tar oozes out
+of it, which tends to smother the fire. Early experiments with coal in
+melting iron ore indicated that soft coal was useless as a substitute
+for charcoal and coke; but later experiments proved that coke of fine
+quality can be made out of this bituminous soft coal, by drawing off the
+tar which makes the trouble. New processes were invented by which
+valuable gas and coal tar are taken out of bituminous coal, leaving, as
+a residue, coke that is equal in quality to that made from the
+Connellsville coal. Fortunes have been made out of the separation of the
+elements of the once despised soft coal. For the coke and each of its
+by-products, coal tar and coal gas, are commercial necessities of life.
+
+The impurities absorbed by the melting iron ore include carbon,
+phosphorus, and silicon. Carbon is the chief cause of the brittleness of
+cast iron. The puddling furnace was invented to remove this trouble. The
+melted ore was stirred on a broad, basin-like hearth, with a
+long-handled puddling rake. The flames swept over the surface, burning
+the carbon liberated by the stirring. It was a hard, hot job for the man
+at the rake, but it produced forge iron, that could be shaped, hot or
+cold, on the anvil.
+
+The next improvement was the process of pressing the hot iron between
+grooved rollers to rid it of slag and other foreign matters collected in
+the furnace. The old way was to hammer the metal free from such
+impurities. This was slow and hard work.
+
+Iron was an expensive and scarce metal until the hot blast-furnace
+cheapened the process of smelting the ore. The puddling furnace and the
+grooved rollers did still more to bring it into general use. The
+railroads developed with the iron industry. Soon they required a metal
+stronger than iron. Steel was far too expensive, though it was just what
+was needed. Efforts were made to find a cheap way to change iron into
+steel. Sir Henry Bessemer solved the problem by inventing the Bessemer
+converter. It is a great closed retort, which is filled with melted pig
+iron. A draught admits air, and the carbon is all burned out. Then a
+definite amount of carbon, just the amount required to change iron into
+steel, is added, by throwing in bars of an alloy of carbon and
+manganese. The latter gives steel its toughness, and enables it to
+resist greater heat without crystallizing and thus losing its temper.
+
+When the carbon has been put in, the retort is closed. The molten metal
+absorbs the alloy, and the product is Bessemer steel. In fifteen minutes
+pig iron can be transformed into ingot steel. The invention made
+possible the use of steel in the construction of bridges, high
+buildings, and ships. It made this age of the world the Age of Steel.
+
+
+
+
+THE AGE OF REPTILES
+
+
+Two big and interesting reptiles we see in the Zoo, the crocodile and
+its cousin, the alligator. In the everglades of Florida both are found.
+The crocodile of the Nile is protected by popular superstition, so it is
+in better luck than ours. The alligators have been killed off for their
+skins, and it is only a matter of time till these lumbering creatures
+will be found only in places where they are protected as the remnants of
+a vanished race. Giant reptiles of other kinds are few upon the earth
+now. The _boa constrictor_ is the giant among snakes. The great tropical
+turtles represent an allied group. Most of the turtles, lizards, and
+snakes are small, and in no sense dominant over other creatures.
+
+The rocks that lie among the coal measures contain fossils of huge
+animals that lived in fresh water and on land, the ancestors of our
+frogs, toads, and salamanders, a group we call amphibians. Some of these
+animals had the form of snakes; some were fishlike, with scaly bodies;
+others were lizard-like or like huge crocodiles. These were the
+ancestors of the reptiles, which became the rulers of land and sea
+during the Mesozoic Era. The rocks that overlie the coal measures
+contain fossils of these gigantic animals.
+
+Strange crocodile-like reptiles, with turtle-like beaks and tusks, but
+no teeth, left their skeletons in the mud of the shores they frequented.
+And others had teeth in groups--grinders, tearers, and cutters--like
+mammals. These had other traits like the old-fashioned, egg-laying
+mammals, the duck-billed platypus, for example, that is still found in
+Australia. Along with the remains of these creatures are found small
+pouched mammals, of the kangaroo kind, in the rocks of Europe and
+America. These land animals saw squatty cycads, and cone-bearing trees,
+the ancestors of our evergreens, growing in forests, and marshes covered
+with luxuriant growths of tree ferns and horsetails, the fallen bodies
+of which formed the recent coal that is now dug in Virginia and North
+Carolina. Ammonites, giant sea snails, with chambered shells that
+reached a yard and more in diameter, and gigantic squids, swam the seas.
+Sea urchins, starfish, and oysters were abundant. Insects flitted
+through the air, but no birds appeared among the trees or beasts in the
+jungles. Over all forms of living creatures reptiles ruled. They were
+remarkable in size and numbers. There were swimming, running, and flying
+forms.
+
+[Illustration: Banded sandstone from Calico Canon, South Dakota]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Opalized wood from Utah]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Restoration of a carnivorous Dinosaur, Allosaurus, from the Upper
+Jurassic and Lower Cretaceous of Wyoming. When erect the animal was
+about 15 feet high]
+
+The fish-reptile, _Ichthyosaurus_, was a hump-backed creature, thirty to
+forty feet long, with short neck, very large head, and long jaw, set
+with hundreds of pointed teeth. Its eye sockets were a foot across. The
+four short limbs were strong paddles, used for swimming. The long,
+slender tail ended in a flat fin. Perfect skeletons of this creature
+have been found. Its rival in the sea was the lizard-like
+_Plesiosaurus_, the small head of which was mounted on a long neck. The
+tail was short, but the paddles were long and powerful. No doubt this
+agile creature held its own, though somewhat smaller than the more
+massively built Ichthyosaurus.
+
+The land reptiles called _Dinosaurs_ were the largest creatures that
+have ever walked the earth. In the American Museum of Natural History,
+in New York, the mounted skeleton of the giant Dinosaur fairly takes
+one's breath away. It is sixty-six feet long, and correspondingly large
+in every part, except its head. This massive creature was remarkably
+short of brains.
+
+The strangest thing about the land reptiles is the fact that certain of
+them walked on their hind legs, like birds, and made three-toed tracks
+in the mud. Indeed, these fossil tracks, found in slate, were called
+bird tracks, until the bones of the reptile skeleton with the bird-like
+foot were discovered. Certain long grooves in the slate, hitherto
+unexplained, were made by the long tail that dragged in the mud.
+
+When the mud dried, and was later covered with sediment of another kind,
+these prints were preserved, and when the bed of rock was discovered by
+quarrymen, the two kinds split apart, showing the record of the stroll
+of a giant along the river bank in bygone days.
+
+The flying reptiles were still more bird-like in structure, though
+gigantic in size. Imagine the appearance of a great lizard with
+bat-like, webbed wings and bat-like, toothed jaws! The first feathered
+fossil bird was discovered in the limestone rock of Bavaria. It was a
+wonderfully preserved fossil, showing the feathers perfectly. Three
+fingers of each "hand" were free and clawed, so that the creature could
+seize its prey, and yet use its feathered wings in flight. The small
+head had jaws set with socketed teeth, like a reptile's, and the long,
+lizard tail of twenty-one bones had a pair of side feathers at each
+joint. This _Archeopteryx_ is the reptilian ancestor of birds. During
+this age of the world, one branch of the reptile group established the
+family line of birds. The bird-like reptiles are the connecting link
+between the two races. How much both birds and reptiles have changed
+from that ancient type, their common ancestor!
+
+I have mentioned but a few of the types of animals that make the
+reptilian age the wonder of all time. One after another skeletons are
+unearthed and new species are found. The Connecticut River Valley, with
+its red sandstones and shales of the Mesozoic Era, is famous among
+geologists, because it preserves the tracks of reptiles, insects, and
+crustaceans. These signs tell much of the life that existed when these
+flakes of stone were sandy and muddy stretches Not many bones have been
+found, however. The thickness of these rocks is between one and two
+miles. The time required to accumulate so much sediment must have been
+very great.
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Model of a three-horned Dinosaur, _Triceratops_, from Cretaceous of
+Montana. Animal in life about 25 feet long]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Mounting the forelegs of _Brontosaurus_, the aquatic Dinosaur]
+
+It is not clear just what caused the race of giant reptiles to decline
+and pass away. The climate did not materially change. Perhaps races grow
+old, and ripe for death, after living long on the earth. It seems as if
+their time was up; and the clumsy giants abdicated their reign, leaving
+dominion over the sea, the air, and the land to those animals adapted to
+take the places they were obliged to vacate.
+
+
+
+
+THE AGE OF MAMMALS
+
+
+The warm-blooded birds and mammals followed the reptiles. This does not
+mean that all reptiles died, after having ruled the earth for thousands
+of years. It means that changes in climate and other life conditions
+were unfavourable to the giants of the cold-blooded races, and gradually
+they passed away. They are represented now on the earth by lesser
+reptiles, which live comfortably with the wild creatures of other
+tribes, but which in no sense rule in the brute creation. They live
+rather a lurking, cautious life, and have to hide from enemies, except a
+few more able kinds, provided with means of defense.
+
+There were mammals on the earth in the days of reptilian supremacy, but
+they were small in size and numbers, and had to avoid any open conflict
+with the giant reptiles, or be worsted in a fight. Now the time came
+when the ruling power changed hands. The mammals had their turn at
+ruling the lower animals. It was the beginning of things as they are
+to-day, for mammals still rule. But many millions of years have probably
+stood between the age when this group of animals first began to swarm
+over the earth, and the time when Man came to be ruler over all created
+things.
+
+Among the reptiles of the period when the sea, the land, and the air
+were swarming with these great creatures were certain kinds that had
+traits of mammals. Others were bird-like. From these reptilian ancestors
+birds and mammals have sprung. No one doubts this. The fossils prove it,
+step by step.
+
+Yet the rocks surprise the geologist with the suddenness with which many
+new kinds of mammals appeared on the earth. Possibly the rocks
+containing the bones of so many kinds were fortunately located. The
+spots may have been morasses where migrating mammals were overwhelmed
+while passing. Possibly conditions favored the rapid development of new
+kinds, and the multiplication of their numbers. Warm, moist climate
+furnished abundant succulent plant food for the herbivors, and these in
+turn furnished prey for the carnivors.
+
+The coal formed during the Tertiary Period gives added proof that the
+plant life was luxuriant. The kinds of trees that grew far north of our
+present warm zones have left in the rocks evidence in the form of
+perfect leaves and cones and other fruits. For instance, magnolias grew
+in Greenland, and palm trees in Dakota. The temperature of Greenland was
+thirty degrees warmer than it is now. Our Northern States lie in a belt
+that must have had a climate much like that of Florida now. Europe was
+correspondingly mild.
+
+A special chapter tells of the gradual development of the horse. One
+hundred different kinds of mammals have been found in the Eocene rocks,
+many of which have representative species at the same time in Europe and
+America. The rocks of Asia probably have similar records.
+
+The Eocene rocks, lowest of the Tertiary strata, contain remains of
+animals the families of which are now extinct. Next overlying the
+Eocene, the Miocene rocks have fossils of animals belonging to modern
+families--rhinoceroses, camels, deer, dogs, cats, horses--but the genera
+of which are now extinct. The Pliocene strata (above the Miocene)
+contains fossils of animals so closely related to the wild animals now
+on the earth as to belong to the same genera. They differ from modern
+kinds only in the species, as the red squirrel is a different species
+from the gray.
+
+So the record in the rocks shows a gradual approach of the mammals to
+the kinds we know, a gradual passing of the mighty forms that ruled by
+size and strength, and the coming of forms with greater intelligence,
+adapted to the change to a colder climate.
+
+It sometimes happens that a farmer, digging a well on the prairie,
+strikes the skeleton of a monster mammal, called the _mastodon_. This
+very thing happened on a neighbour's farm when I was a girl, in Iowa.
+Everybody was excited. The owner of the land dug out every bone, careful
+that the whole skeleton be found. As he expected, the director of a
+museum was glad to pay a high price for the bones.
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Restoration of an aquatic Dinosaur, _Brontosaurus excelsus_, from the
+Upper Jurassic and Lower Cretaceous of Wyoming. The animal in life was
+over 60 feet long]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Restoration of the small carnivorous Dinosaur, _Ornitholestes hermanui_,
+catching a primitive bird _Archaeopteryx_. Upper Jurassic and Lower
+Cretaceous]
+
+The mastodon was about the size of an elephant, with massive limbs, and
+large, heavy head that bore two stout, up-curved tusks of ivory. The
+creature moved in herds like the buffalo from swamp to swamp; and old
+age coming on, the individual, unable to keep up with the herd, sank to
+his death in the boggy ground. The peat accumulated over his bones,
+undisturbed until thousands of years elapse, and the chance digging of a
+well discovers his skeleton.
+
+Frozen in the ice of northern Siberia, near the mouths of rivers, a
+number of mammoths have been found. These are creatures of the elephant
+family, and belonging to the extinct race that lived in the Quaternary
+Period, just succeeding the Tertiary. The ice overtook the specimens,
+and they have been in cold storage ever since. For this reason, both
+flesh and bones are preserved, a rare thing to happen, and rarer still
+to be seen by a scientist.
+
+The ignorant natives made a business of watching the ice masses at the
+river mouth for dark spots that showed where a mammoth was encased in
+the ice. If an iceberg broke off near such a place, the sun might thaw
+the ice front of the glacier, until the hairy monster could at length be
+reached. His long hair served for many uses, and the wool that grew
+under the hair was used as a protection from the Arctic winter. The
+frozen flesh was eaten; the bones carved into useful tools; but the
+chief value of the find was in the great tusks of ivory, that curved
+forward and pointed over the huge shoulders. It was worth a fortune to
+get a pair and sell them to a buyer from St. Petersburg.
+
+One of the finest museum specimens of the mammoth was secured by buying
+the tusks of the dealer, and by his aid tracing the location of the
+carcass, which was found still intact, except that dogs had eaten away
+part of one foreleg, bone and all. From this carefully preserved
+specimen, models have been made, exactly copying the shape and the size
+of the animal, its skin, hair, and other details.
+
+The sabre-toothed tiger, the sharp tusks of which, six to eight inches
+long, made it a far more ferocious beast than any modern tiger of
+tropical jungles, was a Quaternary inhabitant of Europe and America. So
+was a smaller tiger, and a lion. The Irish elk, which stood eleven feet
+high, with antlers that spread ten feet apart at the tips, was monarch
+in the deer family, which had several different species on both
+continents. Wild horses and wild cattle, one or two of great size,
+roamed the woods, while rhinos and the hippopotamus kept near the
+water-courses. Hyenas skulked in the shadows, and acted as scavengers
+where the great beasts of prey had feasted. Sloths and cuirassed
+animals, like giant armadillos, lived in America. Among bears was one,
+the cave bear, larger than the grizzly. True monkeys climbed the trees.
+Flamingo, parrots, and tall secretary birds followed the giant
+_gastornis_, the ancestor of wading birds and ostriches, which stood ten
+feet high, but had wings as small and useless as the auk of later times.
+
+With the entrance of the modern types of trees, came other flowering
+plants, and with them the insects that live on the nectar of flowers.
+Through a long line of primitive forms, now extinct, flowering plants
+and their insect friends conform to modern types. The record is written
+in the great stone book.
+
+The Age of Mammals in America and Europe ended with the gradual rise of
+the continental areas, and a fall of temperature that ushered in the Ice
+Age. With the death of tropical vegetation, the giant mammals passed
+away.
+
+
+
+
+THE HORSE AND HIS ANCESTORS
+
+
+Every city has a horse market, where you may look over hundreds of
+animals and select one of any colour, size, or kind. The least in size
+and weight is the Shetland pony, which one man buys for his children to
+drive or ride. Another man wants a long-legged, deep-chested hunter.
+Another wants heavy draught-horses, with legs like great pillars under
+them, and thick, muscular necks--horses weighing nearly a ton apiece and
+able to draw the heaviest trucks. What a contrast between these slow but
+powerful animals and the graceful, prancing racer with legs like
+pipe-stems--fleet and agile, but not strong enough to draw a heavy load!
+
+All these different breeds of horses have been developed since man
+succeeded in capturing the wild horse and making it help him. Man
+himself was still a savage, and he had to fight with wild beasts, as if
+he were one of them, until he discovered that he could conquer them by
+some power higher than physical strength. From this point on, human
+intelligence has been the power that rules the lower animals. Its
+gradual development is the story of the advance of civilization on the
+earth. Through unknown thousands of years it has gone on, and it is not
+yet finished.
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Restoration of a Siberian mammoth, _Elephas primogenius_, pursued by men
+of the old stone age of Europe. Late Pleistocene epoch]
+
+[Illustration: _By permission of the American Museum of Natural History_
+
+Restoration of a small four-toed ancestor of the horse family, _Eohippus
+venticolus_. Lower Eocene of Wyoming]
+
+Just when and where and how our savage ancestors succeeded in taming the
+wild horse of the plains and the forests of Europe or Asia is unknown.
+Man first made friends with the wild sheep, which were probably more
+docile than wild oxen and horses. We can imagine cold and hungry men
+seeking shelter from storms in rocky hollows, where sheep were huddled.
+How warm the woolly coats of these animals felt to their human
+fellow-creatures crowded in with them in the dark!
+
+It is believed that the primitive men who used stone axes as implements
+and weapons, learned to use horses to aid them in their hunting, and in
+their warfare with beasts and other men. Gradually these useful animals
+were adapted to different uses; and at length different breeds were
+evolved. Climate and food supply had much to do with the size and the
+character of the breeds. In the Shetland Islands the animals are
+naturally dwarfed by the cold, bleak winters, and the scant vegetation
+on which they subsist. In middle Europe, where the summers are long and
+the winters mild, vegetation is luxurious, and the early horses
+developed large frames and heavy muscles. The Shetland pony and the
+Percheron draught-horse are the two extremes of size.
+
+What man has done in changing the types of horses is to emphasize
+natural differences. The offspring of the early heavy horses became
+heavier than their parents. The present draught-horse was produced,
+after many generations, all of which gradually approached the type
+desired. The slender racehorses, bred for speed and endurance rather
+than strength, are the offspring of generations of parents that had
+these qualities strongly marked. Hence came the English thoroughbred and
+the American trotter.
+
+We can read in books the history of breeds of horses. Our knowledge of
+what horses were like in prehistoric times is scant. It is written in
+layers of rock that are not very deep, but are uncovered only here and
+there, and only now and then seen by eyes that can read the story told
+by fossil skeletons of horses of the ages long past.
+
+Geologists have unearthed from time to time skeletons of horses. It was
+Professor Marsh who spent so much time in studying the wonderful beds of
+fossil mammals in the western part of this country, and found among them
+the skeletons of many species of horses that lived here with camels and
+elephants and rhinoceroses and tigers, long before the time of man's
+coming.
+
+How can any one know that these bones belonged to a horse's skeleton?
+Because some of them are like the bones of a modern horse. It is an easy
+matter for a student of animal anatomy to distinguish a horse from a cow
+by its bones. The teeth and the foot are enough. These are important and
+distinguishing characters. It is by peculiarities in the formation of
+the bones of the foot that the different species of extinct horses are
+recognized by geologists.
+
+Wild horses still exist in the wilds of Russia. Remains of the same
+species have been dug out of the soil and found in caves in rocky
+regions. Deeper in the earth are found the bones of horses differing
+from those now living. The bones of the foot indicate a different kind
+of horse--an unknown species. But in the main features, the skeleton is
+distinctly horse-like.
+
+In rocks of deeper strata the fossil bones of other horses are found.
+They differ somewhat from those found in rocks nearer the surface of the
+earth, and still more from those of the modern horse. The older the
+rocks, the more the fossil horse differs from the modern. Could you
+think of a more interesting adventure than to find the oldest rocks that
+show the skeletons of horses?
+
+The foot of a horse is a long one, though we think of it as merely the
+part he walks on. A horse walks on the end of his one toe. The nail of
+the toe we call the "hoof." The true heel is the hock, a sharp joint
+like an elbow nearly half way up the leg. Along each side of the cannon,
+the long bone of this foot, lies a splint of bone, which is the remnant
+of a toe, that is gradually being obliterated from the skeleton. These
+two splints in the modern horse's foot tell the last chapter of an
+interesting story. The earliest American horse, the existence of which
+is proved by fossil bones, tells the first chapter. The story has been
+read backward by geologists. It is told by a series of skeletons, found
+in successive strata of rock.
+
+The "Bad Lands" of the arid Western States are rich in fossil remains of
+horses. Below the surface soil lie the rocks of the Quaternary Period,
+which included the drift laid down by the receding glaciers and the
+floods that followed the melting of the ice-sheet. Under the Quaternary
+lie the Tertiary rocks. These comprise three series, called the Eocene,
+Miocene, and Pliocene, the Eocene being the oldest. In the middle region
+of North America, ponds and marshy tracts were filled in during the
+Tertiary Period, by sediment from rivers; and in these beds of clay and
+other rock debris the remains of fresh-water and land animals are
+preserved. Raised out of water, and exposed to erosive action of wind
+and water, these deposits are easily worn away, for they have not the
+solidity of older rocks. They are the crumbly Bad Lands of the West, cut
+through by rivers, and strangely sculptured by wind and rain. Here the
+fossil horses have been found.
+
+_Eohippus_, the dawn horse, is the name given a skeleton found in 1880
+in the lower Eocene strata in Wyoming. This specimen lay buried in a
+rock formation ages older than that in which the oldest known skeleton
+of this family had been found. Its discovery made a great sensation
+among scientists. This little animal, the skeleton of which is no larger
+than that of a fox, had four perfect toes, and a fifth splint on the
+forefoot, and three toes on the hind foot. The teeth are herbivorous.
+
+_Orohippus_, with a larger skeleton, was found in the middle Eocene
+strata of Wyoming. Its feet are like those of its predecessor, except
+that the splint is gone. The teeth as well as the feet are more like
+those of the modern horse.
+
+_Mesohippus_, the three-toed horse, found in the Miocene, shows the
+fourth toe reduced to splints, and the skeleton as big as that of a
+sheep. In this the horse family becomes fairly established.
+
+_Hypohippus_, the three-toed forest horse, found in the middle Miocene
+strata of Colorado, is a related species, but not a direct ancestor of
+the modern horse.
+
+_Neohipparion_, the three-toed desert horse, from the upper Miocene
+strata, shows the three toes still present. But the Pliocene rocks
+contain fossils showing gradual reduction of the two side toes,
+modification of the teeth, and increase in size of the skeleton.
+
+_Protohippus_ and _Pliohippus_, the one-toed species from the Pliocene
+strata, illustrate these changes. They were about the size of small
+ponies.
+
+_Equus_, the modern horse, was represented in the Pliocene strata by a
+species, now extinct, called _Equus Scotti_. This we may regard as the
+true wild horse of America, for it was as large as the domesticated
+horse, and much like it, though more like a zebra in some respects. No
+one can tell why these animals, once abundant in this country, became
+extinct at the end of the Tertiary Period. But this is undoubtedly true.
+
+The types described form a series showing how the ancestors of the
+modern horse, grazing on the marshy borders of ancient ponds, lived and
+died, generation after generation, through a period covering thousands,
+possibly millions, of years. Along the sides of the crumbling buttes
+these ancient burying-grounds are being uncovered. Within a dozen years
+several expeditions, fitted out by the American Museum of Natural
+History, have searched the out-cropping strata in Dakota and Wyoming for
+bones of mammals known to have lived at the time the strata were forming
+in the muddy shallows along the margins of lake and marsh. Duplicate
+skeletons of the primitive horse types above have been found, and vast
+numbers of their scattered bones. Each summer geological excursions will
+add to the wealth of fossils of this family collected in museums.
+
+The Tertiary rocks in Europe yield the same kind of secrets. The region
+of Paris overlies the estuary of an ancient river. When the strata are
+laid bare by the digging of foundations for buildings, bones are found
+in abundance. Cuvier was a famous French geologist who made extensive
+studies of the remains of the prehistoric animals found in this old
+burial-place called by scientists the Paris basin. He believed that the
+dead bodies floated down-stream and accumulated in the mud of the
+delta, where the tide checked the river's current.
+
+Skeletons of the Hipparion, a graceful, three-toed horse, were found in
+numbers in the strata of the Miocene time. This animal lived in Europe
+while the Pliohippus and the Protohippus were flourishing in America.
+
+A great number of species of tapir-like animals left their bones in the
+Paris basin, among them a three-hoofed animal which may have been the
+connecting link between the horse and the tapir families. Cuvier found
+the connecting link between tapirs and cud-chewing mammals.
+
+
+
+
+THE AGE OF MAN
+
+
+The hairy, woolly mammoth was one of the giant mammals that withstood
+the cold of the great ice flood, when the less hardy kinds were cut off
+by the changing climate of the northern half of Europe and America. In
+caves where the wild animals took refuge from their enemies, skeletons
+of men have been found with those of the beasts. With these chance
+skeletons have been found rude, chipped stone spear-heads, hammers, and
+other tools. With these the savage ancestors of our race defended
+themselves, and preyed on such animals as they could use for food. They
+hunted the clumsy mammoth successfully, and shared the caverns in the
+rocks with animals like the hyena, the sabre-toothed tiger, and the cave
+bear, which made these places their homes. In California a human skull
+was found in the bed of an ancient river, which was buried by a lava
+flow from craters long ago extinct. With this buried skull a few
+well-shaped but rough stone tools were found. This man must have lived
+when the great ice flood was at its height.
+
+In southern France, caves have been opened that contained bones and
+implements of men who evidently lived by fishing and hunting. Bone
+fish-hooks showed skill in carving with the sharp edges of flint
+flakes. A spirited drawing of a mammoth, made on a flat, stone surface,
+is a proof that savage instincts were less prominent in these cave men
+than in those who fought the great reindeer and the mammoth farther
+north.
+
+In later times men of higher intelligence formed tribes, tamed the wild
+horse, the ox, and the sheep, and made friends with the dog. Great heaps
+of shells along the shores show where the tribes assembled at certain
+times to feast on oysters and clams. Bones of animals used as food, and
+tools, are found in these heaps, called "kitchen-middens." These are
+especially numerous in Northern Europe. The stone implements used by
+these tribes were smoothly polished. A higher intelligence expressed
+itself also by the making of utensils out of clay. This pottery has been
+found in shell heaps. So the rude cave man, who was scarcely less a wild
+beast than the animals which competed with him for a living and a
+shelter from storms and cold, was succeeded by a higher man who brought
+the brutes into subjection by force of will and not by physical
+strength.
+
+The lake-dwellers, men of the Bronze Age, built houses on piles in the
+lakes of Central Europe. About sixty years ago the water was low, and
+these relics of a vanished race were first discovered. The lake bottoms
+were scraped for further evidences of their life. Tools of polished
+stone and of bronze were taken up in considerable numbers. Stored
+grains and dried fruits of several kinds were found. Ornamental
+trinkets, weapons of hunters and warriors, and agricultural tools tell
+how the people lived. Their houses were probably built over the water as
+a means of safety from attack of beasts or hostile men.
+
+In our country the mound-builders have left the story of their manners
+of life in the spacious, many-roomed tribal houses, built underground,
+and left with a great variety of relics to the explorers of modern
+times. These people worked the copper mines, and hammered and polished
+lumps of pure metal into implements for many uses. With these are tools
+of polished stone. Stores of corn were found in many mounds scattered in
+the Mississippi Valley.
+
+The cliff-dwellers of the mesas of Arizona and New Mexico had habits
+like those of the mound-builders, and the Aztecs, a vanished race in the
+Southwest, at whose wealth and high civilization the invading Spaniards
+under Cortez marvelled. The plastered stone houses of the cliff-dwelling
+Indians had many stories and rooms, each built to house a tribe, not
+merely a family.
+
+The Pueblo, the Moqui, and the Zuni Indians build similar dwellings
+to-day, isolated on the tops of almost inaccessible mesas.
+
+Millions of years have passed since life appeared on the earth.
+Gradually higher forms have followed lower ones in the sea and on the
+land. But not all of the lower forms have gone. All grades of plants
+and animals still flourish, but the dominant class in each age is more
+highly organized than the class that ruled the preceding age.
+
+To discover the earth's treasure, and to turn it to use; to tame wild
+animals and wild plants, and make them serve him; to create ever more
+beautiful and more useful forms in domestication; to find out the
+earth's life story, by reading the pages of the great stone book--these
+are undertakings that waited for man's coming.
+
+       *       *       *       *       *
+
+
+
+
+PART II
+
+THE SKY
+
+       *       *       *       *       *
+
+
+
+
+EVERY FAMILY A "STAR CLUB"
+
+
+The best family hobby we have ever had is the stars. We have a star club
+with no dues to pay, no officers to boss us, and only three rules:
+
+1. We shall have nothing but "fun" in this club--no hard work. Therefore
+no mathematics for us!
+
+2. We can't afford a telescope. Therefore we must be satisfied with what
+bright eyes can see.
+
+3. No second-hand wonders for us! We want to see the things ourselves,
+instead of depending on books.
+
+You can't imagine what pleasure we have had in one short year! The baby,
+of course, was too young to learn anything, and besides he was in bed
+long before the stars came out. But Ruth, our seven-year-old, knows ten
+of the fifteen brightest stars; and she can pick out twelve of the most
+beautiful groups or constellations. We grown-ups know all of the
+brightest stars, and all forty-eight of the most famous constellations.
+And the whole time we have given to it would not exceed ten minutes a
+day!
+
+And the best part is the _way_ we know the stars. The sky is no longer
+bewildering to us. The stars are not cold, strange, mysterious. They are
+friends. We know their faces just as easily as you know your playmates.
+For instance, we know Sirius, because he is the brightest. We know
+Castor and Pollux, because they are twins. We know Regulus, because he
+is in the handle of the Sickle. And some we know by their colours. They
+are just as different as President Taft, "Ty" Cobb, Horace Fletcher and
+Maude Adams. And quite as interesting!
+
+What's more, none of us can ever get lost again. No matter what strange
+woods or city we go to, we never get "turned around." Or if we do, we
+quickly find the right way by means of the sun or the stars.
+
+Then, too, our star club gives us all a little exercise when we need it
+most. Winter is the time when we all work hardest and have the fewest
+outdoor games. Winter is also the best time for young children to enjoy
+the stars, because it gets dark earlier in winter--by five o'clock, or
+long before children go to bed. It is pleasant to go out doors for half
+an hour before supper and learn one new star or constellation.
+
+Again, it is always entertaining because every night you find the old
+friends in new places. No two nights are just the same. The changes of
+the moon make a great difference. Some nights you enjoy the moonlight;
+other nights you wish there were no moon, because it keeps you from
+spying out some new star. We have a little magazine that tells us all
+the news of the stars and the planets and the comets _before_ the things
+happen! We pay a dollar a year for it. It is called the _Monthly
+Evening Sky Map_.
+
+When we first became enthusiastic about stars, the father of our family
+said: "Well, I think our Star Club will last about two years. I judge it
+will cost us about two dollars and we shall get about twenty dollars
+worth of fun out of it." But in all three respects father was mistaken.
+
+Part of the two dollars father spoke of went for a book called "The
+Friendly Stars," and seventy-five cents we spent for the most
+entertaining thing our family ever bought--a planisphere. This is a
+device which enables us to tell just where any star is, at any time, day
+or night, the whole year. It has a disc which revolves. All we have to
+do is to move it until the month and the day come right opposite the
+very hour we are looking at it, and then we can tell in a moment which
+stars can be seen at that time. Then we go down the street where there
+is a good electric light at the corner and we hold our planisphere up,
+almost straight overhead. The light shines through, so that we can read
+it, and it is just as if we had a map of the heavens. We can pick out
+all the interesting constellations and name them just as easily as we
+could find the Great Lakes or Rocky Mountains in our geography.
+
+We became so eager not to miss any good thing that father got another
+book. Every birthday in our family brought a new star book, until now we
+have about a dozen--all of them interesting and not one of them having
+mathematics that children cannot understand. So I think we have spent on
+stars fifteen dollars more than we needed to spend (but I'm glad we did
+it), and I think we have had about two hundred dollars worth of fun!
+Yes, when I think what young people spend on ball games, fishing,
+tennis, skating, and all the other things that children love, I am sure
+our family has had about two hundred dollars worth of fun out of stars.
+And there is more to come!
+
+You would laugh to know why I enjoy stars so much. I have always studied
+birds and flowers and trees and rocks and shells so much that I was
+afraid to get interested in stars. I thought it wouldn't rest me. But
+it's a totally different kind of science from any I ever studied! There
+are no families, genera, and species among the stars, thank Heaven!
+That's one reason they refresh me. Another is that no one can press them
+and put them in a herbarium, or shoot them and put them in a museum. And
+another thing about them that brings balm to my spirit is that no human
+being can destroy their beauty. No one can "sub-divide" Capella and fill
+it with tenements. No one can use Vega for a bill-board. Ah, well! we
+must not be disturbed if every member of our family has a different
+point of view toward the stars; we can all enjoy and love them in our
+own ways.
+
+How would you like to start a Star Club like ours? You ought to be able
+to persuade your family to form one, because it need not cost a cent.
+Perhaps this book will interest them all, but the better way is for you
+to read about one constellation and then go out with some of the family
+and find it. This book does not tell about wonderful things you can
+never see; it tells about the wonderful things all of us can see.
+
+I wish you success with your Star Club. Perhaps your uncles and aunts
+will start clubs, too. We have three Star Clubs in our family--one in
+New York, one in Michigan, and one in Colorado. Last winter the
+"Colorado Star Gazers" sent this challenge to the "New Jersey
+Night-Owls:" "_We bet you can't see Venus by daylight!_"
+
+That seemed possible, because during that week the "evening star" was by
+far the brightest object in the sky. But father and daughter searched
+the sky before sunset in vain, and finally we had to ask the "Moonstruck
+Michiganders" how to see Venus while the sun was shining. Back came
+these directions on a postal-card: "Wait until it is dark and any one
+can see Venus. Then find some tree, or other object, which is in line
+with Venus and over which you can just see her. Put a stake where you
+stand. Next day go there half an hour before sunset, and stand a little
+to the west. You will see Venus as big as life. The next afternoon you
+can find her by four o'clock. And if you keep on you will see her day
+before yesterday!"
+
+That was a great "stunt." We did it; and there are dozens like it you
+can do. And that reminds me that father was mistaken about our interest
+lasting only two years. We know that it will not die till we do. For,
+even if we never get a telescope, there will always be new things to
+see. Our club has still to catch Algol, the "demon's eye," which goes
+out and gleams forth every three days, because it is obscured by some
+dark planet we can never see. And we have never yet seen Mira the
+wonderful, which for some mysterious reason dies down to ninth magnitude
+and then blazes up to second magnitude every eleventh month.
+
+Ah, yes, the wonders and the beauties of astronomy ever deepen and
+widen. Better make friends with the stars now. For when you are old
+there are no friends like old friends.
+
+
+
+
+THE DIPPERS AND THE POLE STAR
+
+
+I never heard of any boy or girl who didn't know the Big Dipper. But
+there is one very pleasant thing about the Dipper which children never
+seem to know. With the aid of these seven magnificent stars you can find
+all the other interesting stars and constellations. So true is this that
+a book has been written called "The Stars through a Dipper."
+
+To illustrate, do you know the _Pointers_? I mean the two stars on the
+front side of the Dipper. They point almost directly toward the Pole
+star, or North star, the correct name of which is Polaris. Most children
+can see the Pole star at once because it is the only bright star in that
+part of the heavens.
+
+But if you can't be sure you see the right one, a funny thing happens.
+Your friend will try to show you by pointing, but even if you look
+straight along his arm you can't always be sure. And then, if he tries
+to tell you how far one star is from another, he will try to show you by
+holding his arms apart. But that fails also. And so, we all soon learn
+the easiest and surest way to point out stars and measure distances.
+
+The easiest way to tell any one how to find a star is to get three
+stars in a straight line, or else at right angles.
+
+The surest way to tell any one how far one star is from another is by
+"degrees." You know what degrees are, because every circle is divided
+into 360 of them. And if you will think a moment, you will understand
+why we can see only half the sky at any one time, or 180 degrees,
+because the other half of the sky is on the other side of the earth.
+Therefore, if you draw a straight line from one horizon, clear up to the
+top of the sky and down to the opposite horizon, it is 180 degrees long.
+And, of course, it is only half that distance, or 90 degrees, from
+horizon to zenith. (Horizon is the point where earth and sky seem to
+meet, and zenith is the point straight over your head.)
+
+Now ninety degrees is a mighty big distance in the sky. The Pole star is
+nothing like ninety degrees from the Dipper. It is only twenty-five
+degrees, or about five times the distance between the Pointers. And now
+comes the only thing I will ask you to remember. Look well at the two
+Pointers, because the distance between them, five degrees, is the most
+convenient "foot rule" for the sky that you will ever find. Most of the
+stars you will want to talk about are from two to five times that
+distance from some other star that you and your friends are sure of.
+Perhaps this is a little hard to understand. If so, read it over several
+times, or get some one to explain it to you, for when you grasp it, it
+will unlock almost as many pleasures as a key to the store you like the
+best.
+
+Now, let's try our new-found ruler. Let us see if it will help us find
+the eighth star in the Dipper. That's a famous test of sharp eyes. I
+don't want to spoil your pleasure by telling you too soon where it is.
+Perhaps you would rather see how sharp your eyes are before reading any
+further. But if you can't find the eighth star, I will tell you where to
+look.
+
+Look at the second star in the Dipper, counting from the end of the
+handle. That is a famous star called Mizar. Now look all around Mizar,
+and then, if you can't see a little one near it, try to measure off one
+degree. To do this, look at the Pointers and try to measure off about a
+fifth of the distance between them. Then look about one degree (or less)
+from Mizar, and I am sure you will see the little beauty--its name is
+Alcor, which means "the cavalier" or companion. The two are sometimes
+called "_the horse and rider_"; another name for Alcor is Saidak, which
+means "the test." I shall be very much disappointed if you cannot see
+Saidak, because it is not considered a hard test nowadays for sharp
+eyes.
+
+Aren't these interesting names? Mizar, Alcor, Saidak. They sound so
+Arabian, and remind one of the "Arabian Nights." At first, some of them
+will seem hard, but you will come to love these old names. I dare say
+many of these star names are 4,000 years old. Shepherds and sailors
+were the first astronomers. The sailors had to steer by the stars, and
+the shepherds could lie on the ground and enjoy them without having to
+twist their necks. They saw and named Alcor, thousands of years before
+telescopes were invented, and long before there were any books to help
+them. They saw the demon star, too, which I have never seen. It needs
+patience to see those things; sharp eyes are nothing to be proud of,
+because they are given to us. But patience is something to be eager
+about, because it costs us a lot of trouble to get it.
+
+Let's try for it. We've had a test of sight. Now let's have a test of
+patience. It takes more patience than sharpness of sight to trace the
+outline of the Little Dipper. It has seven stars, too, and the Pole star
+is in the end of the handle. Do you see two rather bright stars about
+twenty-five degrees from the Pole? I hope so, for they are the only
+brightish stars anywhere near Polaris. Well, those two stars are in the
+outer rim of the Little Dipper. Now, I think you can trace it all; but
+to make sure you see the real thing, I will tell you the last secret.
+The handle of the Big Dipper is bent _back_; the handle of the Little
+Dipper is bent _in_.
+
+Now, if you have done all this faithfully, you have worked hard enough,
+and I will reward you with a story. Once upon a time there was a
+princess named Callisto, and the great god Jupiter fell in love with
+her. Naturally, Jupiter's wife, Juno, wasn't pleased, so she changed the
+princess into a bear. But before this happened, Callisto became the
+mother of a little boy named Arcas, who grew up to be a mighty hunter.
+One day he saw a bear and he was going to kill it, not knowing that the
+bear was really his own mother. Luckily Jupiter interfered and saved
+their lives. He changed Arcas into a bear and put both bears into the
+sky. Callisto is the Big Bear, and Arcas is the Little Bear. But Juno
+was angry at that, and so she went to the wife of the Ocean and said,
+"Please, never let these bears come to your home." So the wife of the
+Ocean said, "I will never let them sink beneath the waves." And that is
+why the Big and the Little Dipper never set. They always whirl around
+the Pole star. And that is why you can always see them, though some
+nights you would have to sit up very late.
+
+Is that a true story? No. But, I can tell you a true one that is even
+more wonderful. Once upon a time, before the bear story was invented and
+before people had tin dippers, they used to think of the Little Dipper
+as a little dog. And so they gave a funny name to the Pole star. They
+called it Cynosura, which means "the dog's tail." We sometimes say of a
+great man, "he was the cynosure of all eyes," meaning that everybody
+looked at him. But the original cynosure was and is the Pole star,
+because all the stars in the sky seem to revolve around it. The two
+Dippers chase round it once every twenty-four hours, as you can convince
+yourself some night when you stay up late. So that's all for to-night.
+
+What! You want another true story? Well, just one more. Once upon a time
+the Big Dipper was a perfect cross. That was about 50,000 years ago.
+Fifty thousand years from now the Big Dipper will look like a steamer
+chair. How do I know that? Because, the two stars at opposite ends of
+the Dipper are going in a direction different from the other five stars.
+How do I know that? Why, I don't know it. I just believe it. There are
+lots of things I don't know, and I'm not afraid to say so. I hope you
+will learn how to say "I don't know." It's infinitely better than
+guessing; it saves trouble, and people like you better, because they see
+you are honest. I don't know how the stars in the Big Dipper are moving,
+but the men who look through telescopes and study mathematics say the
+end stars do move in a direction opposite to the others, and they say
+the Dipper _must_ have looked like a cross, and will look like a dipper
+long, long after we are dead. And I believe them.
+
+
+
+
+CONSTELLATIONS YOU CAN ALWAYS SEE
+
+
+There are forty-eight well known constellations, but of these only about
+a dozen are easy to know. I think a dozen is quite enough for children
+to learn. And therefore, I shall tell you how to find only the showiest
+and most interesting.
+
+The best way to begin is to describe the ones that you can see almost
+every night in the year, because you may want to begin any month in the
+year, and you might be discouraged if I talked about things nobody could
+see in that month. There are five constellations you can nearly always
+see, and these are all near the Pole star.
+
+Doubtless you think you know two of them already--the Big and the Little
+Dipper. Ah, I forgot to tell you that these dippers are not the real
+thing. They are merely parts of bigger constellations and their real
+names are Great Bear and Little Bear. The oldest names are the right
+ones. Thousands of years ago, when the Greeks named these groups of
+stars, they thought they looked like two bears. I can't see the
+resemblance.
+
+But for that matter all the figures in the sky are disappointing. The
+people who named the constellations called them lions, and fishes, and
+horses, and hunters, and they thought they could see a dolphin, a
+snake, a dragon, a crow, a crab, a bull, a ram, a swan, and other
+things. But nowadays we cannot see those creatures. We can see the stars
+plainly enough, and they do make groups, but they do not look like
+animals. I was greatly disappointed when I was told this; but I soon got
+over it, because new wonders are always coming on. I think the only
+honest thing to do is to tell you right at the start that you cannot see
+these creatures very well. You will spoil your pleasure unless you take
+these resemblances good-naturedly and with a light heart. And you will
+also spoil your pleasure if you scold the ancients for naming the
+constellations badly. Nobody in the world would change those old names
+now. There is too much pleasure in them. Besides, I doubt if we could do
+much better. I believe those old folks were better observers than we.
+And I believe they had a lighter fancy.
+
+Let us, too, be fanciful for once. I have asked my friend, Mrs. Thomas,
+to draw her notion of some of these famous creatures of the sky. You can
+draw your idea of them too, and it is pleasant to compare drawings with
+friends. There is only one way to see anything like a Great Bear. You
+have to imagine the Dipper upside down and make the handle of the Dipper
+serve for the Bear's tail. What a funny bear to drag a long tail on the
+ground! Miss Martin says he looks more like a chubby hobby-horse. You
+will have to make the bowl of the Dipper into hind legs and use all the
+other stars, somehow, to make a big, clumsy, four-legged animal. And
+what a monster he is! He measures twenty-five degrees from the tip of
+his nose to the root of his tail. Yes, all those miscellaneous faint
+stars you see near the Big Dipper belong to the Great Bear.
+
+[Illustration: Orion fighting the Bull. Above are Orion's two dogs]
+
+[Illustration: The Little Bear, the Queen in her chair, the Twins and
+the Archer]
+
+How the Great Bear looked to the people who named it thousands of years
+ago, we probably shall never know. They left no books or drawings, so
+far as I know. But in every dictionary and book on astronomy you can
+find these bears and other animals drawn so carefully and beautifully
+that it seems as if they _must_ be in the sky, and we must be too dull
+to see them. It is not so. Look at the pictures in this book and, you
+will see that the stars do not outline the animals. Many of them come at
+the wrong places. And so it is with all the costly books and charts and
+planispheres. It is all very interesting, but it isn't true. It's just
+fancy. And when you once understand that it isn't true, you will begin
+to enjoy the fancy. Many a smile you will have, and sometimes a good
+laugh. For instance, the English children call the Dipper "Charles's
+wain" or "the wagon." And the Romans called it "the plough." They
+thought of those seven stars as oxen drawing a plough.
+
+Well, that's enough about the two Bears. I want to tell you about the
+other three constellations you can nearly always see. These are the
+Chair, the Charioteer, and Perseus (pronounced _per'soos_).
+
+The Chair is the easiest to find, because it is like a very bad W, and
+it is always directly opposite the big Dipper, with the Pole star half
+way between the two constellations. There are five stars in the W, and
+to make the W into a Chair you must add a fainter star which helps to
+make the square bottom of the chair. But what a crazy piece of
+furniture! I have seen several ways of drawing it, but none of them
+makes a comfortable chair. I should either fall over backward, or else
+the back of the chair would prod me in the small of my back. The correct
+name of this constellation is Cassiopeia's Chair.
+
+I think this is enough to see and enjoy in one night. To-morrow night
+let us look for the Charioteer.
+
+I love the Charioteer for several reasons. One is that it makes a
+beautiful pentagon, or five-sided figure, with its five brightest stars.
+Another is that it contains the second-brightest star in the northern
+part of the heavens, Capella. The only star in the north that is
+brighter is Vega, but Vega is bluish white or creamy.
+
+If you haven't already found the five-sided figure, I will tell you how
+to find Capella. Suppose you had a gun that would shoot anything as far
+as you wish. Shoot a white string right through the Pointers and hit the
+Pole star. Then place your gun at the Pole star and turn it till it is
+at right angles to that string you shot. Aim away from the big Dipper,
+shoot a bullet forty-five degrees and it will hit Capella.
+
+If that plan doesn't work, try this. Start with the star that is at the
+bottom of the Dipper and nearest the handle. Draw a line half-way
+between the two Pointers and keep on till you come to the first bright
+star. This is Capella, and the distance is about fifty degrees.
+
+Capella means "a kid," or "little goat," and that reminds me of the
+third reason why I enjoy so much the constellation of which Capella is
+the brightest star. In the old times they sometimes called this
+five-sided figure "the goat-carrier." And the shepherds thought they
+could see a man carrying a little goat in his left hand. I am sure you
+can see the kid they meant. It is a triangle of faint stars which you
+see near Capella. That's enough for to-night.
+
+To-morrow night let us look for Perseus. I dare say you know that old
+tale about Perseus rescuing the princess who was chained upon a rock.
+(He cut off the snaky head of Medusa and showed it to the dragon that
+was going to devour the princess, and it turned the monster to stone.
+Remember?) Well, there are constellations named after all the people in
+that story, but although they contain many showy stars, I could never
+make them look like a hero, a princess, a king, and a queen. I do not
+even try to trace out all of Perseus. For I am satisfied to enjoy a very
+beautiful part of it which is called the "Arc of Perseus."
+
+An arc, you know, is a portion of a circle. And the way to find this arc
+is to draw a curve from Capella to Cassiopeia. On nights that are not
+very clear I can see about seven stars in this Arc of Perseus. And the
+reason I love it so much is that it is the most beautiful thing, when
+seen through an opera-glass, that I know. You could never imagine that a
+mere opera-glass would make such a difference. The moment I put it to my
+eyes about a dozen more stars suddenly leap into my sight in and near
+the Arc of Perseus. That's enough. No more stories to-night.
+
+
+
+
+WINTER CONSTELLATIONS
+
+
+By winter constellations I mean those you can see in winter at the
+pleasantest time--the early evening. And I want you to begin with the
+Northern Cross. I hope you can see this before Christmas, for, after
+that, it may be hidden by trees or buildings in the west and you may not
+see it again for a long while. This is because the stars seem to rise in
+the east and set in the west. To prove this, choose some brilliant star
+you can see at five or six o'clock; get it in line with some bush or
+other object over which you can just see it. Put a stake where you
+stand, and then go to the same spot about eight o'clock or just before
+you go to bed. You can tell at once how much the star seems to have
+moved westward.
+
+Another thing, every star rises four minutes later every night, and
+therefore the sky looks a little different at the same hour every
+evening. The stars in the north set for a short time only, but when
+those toward the south set they are gone a long time. For instance, the
+brightest star of all is Sirius, the Dog Star, which really belongs to
+the southern hemisphere. There are only about three months in the year
+when children who go to bed by seven o'clock can see it--January,
+February, and March.
+
+So now you understand why I am so eager that you should not miss the
+pleasure of seeing the famous Northern Cross. But although it is a big
+cross, and easy to find, after you know it, I have never yet known a boy
+who could show it to another boy simply by pointing at it. The surest
+and best way to find it is learn three bright stars first--Altair, Vega,
+and Deneb.
+
+Altair is the brightest star in the Milky Way. It is just at the edge of
+the Milky Way, and you are to look for three stars in a straight line,
+with the middle one brightest. Those three stars make the constellation
+called "the Eagle." The body of the eagle is Altair, and the other two
+stars are the wings. I should say that Altair is about five degrees from
+each of his companions. It is worth half an hour's patient search to
+find the Eagle. Now these three stars in the Eagle point straight toward
+the brightest star in the northern part of the sky--Vega.
+
+To make sure of it, notice four fainter stars near it which make a
+parallelogram--a sort of diamond. These stars are all part of a
+constellation called "the Lyre." If you try to trace out the old musical
+instrument, you will be disappointed; but here is a game worth while.
+Can you see a small triangle made by three stars, of which Vega is one?
+Well, one of those stars is double, and with an opera-glass you can see
+which it is. On very clear nights some people with very sharp eyes can
+see them lying close together, but I never could.
+
+At last we are ready to find the celebrated Northern Cross. First draw a
+line from Altair to Vega. Then draw a line at right angles to this,
+until you come to another bright star--Deneb--which is about as far from
+Vega as Vega is from Altair. Now this beautiful star, Deneb, is the top
+of the Northern Cross. I can't tell you whether the Cross will be right
+or wrong side up when you see it, or on its side. For every
+constellation is likely to change its position during the night, as you
+know from watching the Dipper. But you can tell the Cross by these
+things. There are six stars in it. It is like a kite made of two sticks.
+There are three stars in the crosspiece and four in the long piece.
+Deneb, the brightest star in the cross, is at the top of the long stick.
+
+But you mustn't expect to see a perfect cross. There is one star that is
+a little out of place, and sometimes my fingers fairly "itch to put it
+where it belongs." It is the one that ought to be where the long stick
+of your kite is tacked to the crosspiece. And one of the stars is
+provokingly faint, but you can see it. Counting straight down the long
+piece, it is the third one from Deneb that is faint. It is where it
+ought to be, but I should like to make it brighter. Have you the Cross
+now? If not, have patience. You can't be a "true sport" unless you are
+patient. You can't be a great ball-player, or hunter, or any thing else,
+without resisting, every day, that sudden impulse to "quit the game"
+when you lose. Be a "good loser," smile and try again. That is better
+than to give up, or to win by cheating or sharp practice.
+
+This is the last thing I want you to see in the northern part of the
+sky; and if you have done a good job, let us celebrate by having a
+story.
+
+Once upon a time a cross didn't mean so much to the world as it does
+now. That was before Christ was born. In those old times people did not
+think of the Northern Cross as a cross. They thought of it as a Swan,
+and you can see the Swan if you turn the Cross upside down. Deneb will
+then be in the tail of the Swan, and the two stars which used to be at
+the tips of the crosspiece now become the wings. Is that a true story?
+Yes. If we lived in Arabia the children there could tell us what Deneb
+means. It means "the tail."
+
+Another story? Well, do you see the star in the beak of the Swan, or
+foot of the Cross? What color is it? White? Well, they say this white
+star is really made up of two stars--one yellow and the other blue. That
+is one reason I want to buy a telescope when I can afford it, for even
+the smallest telescope will show that. And Mr. Serviss says that even a
+strong field-glass will help any one see this wonder.
+
+I can't tell you about all the winter constellations in one chapter. We
+have made friends of the northern ones. Now let's see the famous
+southern ones. And let's start a new chapter.
+
+
+
+
+ORION, HIS DOGS, AND THE BULL
+
+
+The most gorgeous constellation in the whole sky is Orion. I really pity
+any one who does not know it, because it has more bright stars in it
+than any other group. Besides, it doesn't take much imagination to see
+this mighty hunter fighting the great Bull. I dare say half the people
+in the United States know Orion and can tell him as quick as they see
+him by the famous "belt of Orion."
+
+This belt is made of three stars, each of which is just one degree from
+the next. That is why the English people call these three stars "the ell
+and yard." Another name for them is "the three kings." You can see the
+"sword of Orion" hanging down from his belt.
+
+As soon as you see these things you will see the four bright stars that
+outline the figure of the great hunter, but only two of them are of the
+first magnitude. The red one has a hard name--Betelgeuse (pronounced
+_bet-el-guz'_). That is a Frenchified word from the Arabic, meaning
+"armpit," because this star marks the right shoulder of Orion. The other
+first-magnitude star is the big white one in the left foot. Its name is
+Rigel (pronounced _re'-jel_) from an Arabian word meaning "the foot."
+
+You can see the giant now, I am sure. Over his left arm hangs a lion's
+skin which he holds out to shield him from the bull's horns. See the
+shield--about four rather faint stars in a pretty good curve? Now look
+for his club which he holds up with his right hand so as to smite the
+bull. See the arm and the club--about seven stars in a rather poor
+curve--beyond the red star Betelgeuse? Now you have him, and isn't he a
+wonder!
+
+It is even easier to see the Bull which is trying to gore Orion. Look
+where Orion is threatening to strike, and you will see a V. How many
+stars in that V? Five. And which is the brightest? That red one at the
+top of the left branch of the V? Yes. That V is the face of the Bull and
+that red star is the baleful eye of the angry Bull which is lowering his
+head and trying to toss Orion. The name of that red eye is Aldebaran
+(pronounced _al-deb'-ar-an_).
+
+I wish Aldebaran meant "red eye," but it doesn't. It is an old Arabian
+word meaning the "hindmost," or the "follower," because every evening it
+comes into view about an hour after you can see the famous group of
+stars called the Pleiades, which are in the shoulder of the Bull.
+
+I do not care to trace the outline of this enormous bull, but his horns
+are a great deal longer than you think at first. If you will extend the
+two arms of that V a long way you will see two stars which may be called
+the tips of his horns. One of these stars really belongs in another
+constellation--our old friend the Charioteer, the one including
+Capella. Wow! what a pair of horns!
+
+But now we come to the daintiest of all constellations--the Seven
+Sisters, or Pleiades (pronounced _plee'-a-deez_).
+
+I can see only six of them, and there is a famous old tale about the
+"lost Pleiad." But I needn't describe them. Every child finds them by
+instinct. Some compare them to a swarm of bees; some to a rosette of
+diamonds; some to dewdrops. But I would not compare them to a dipper as
+some do, because the real Little Dipper is very different. The light
+that seems to drip from the Pleiades is quivering, misty, romantic,
+magical. No wonder many children love the Pleiades best of all the
+constellations. No wonder the poets have praised them for thousands of
+years. The oldest piece of poetry about them that I know of was written
+about 1,500 years before Christ. You can find it in the book of Job. But
+the most poetic description of the Pleiades that I have ever read is in
+Tennyson's poem "Locksley Hall," in which he says they "glitter like a
+swarm of fireflies tangled in a silver braid."
+
+There are a great many old tales about the lost Pleiad. One is that she
+veiled her face because the ancient city of Troy was burned. Another
+story says she ceased to be a goddess when she married a man and became
+mortal. Some people think she was struck by lightning. Others believe
+the big star, Canopus, came by and ran away with her. Still others
+declare she was a new star that appeared suddenly once upon a time, and
+after a while faded away.
+
+For myself, I do not believe any of these stories. One reason why I
+don't is that a seventh star is really there, and many people can really
+see it. Indeed, there are some people so sharp-eyed that on clear nights
+they can see anywhere from eight to eleven. And, what is more, they can
+draw a map or chart showing just where each star seems to them to be.
+
+But the most wonderful stories about the Pleiades are the true stories.
+One is that there are really more than 3,000 stars among the Pleiades.
+Some of them can be seen only with the biggest telescopes. Others are
+revealed only by the spectroscope. And some can be found only by means
+of photography.
+
+But the most amazing thing about the Pleiades is the distances between
+them. They look so close together that you would probably say "the moon
+seems bigger than all of them put together." Sometimes the moon comes
+near the Pleiades, and you expect that the moon will blot them all out.
+But the astronomers say the full moon sails through the Pleiades and
+covers only one of them at a time, as a rule. They even say it is
+possible for the moon to pass through the Pleiades without touching one
+of them! I should like to see that. If anything like it is going to
+occur, the magazine I spoke of in the first chapter will tell me about
+it. And you'd better believe I will stay up to see that, if it takes all
+night!
+
+There are two more constellations in the southern part of the sky that
+ought to be interesting, because they are the two hunting dogs that help
+Orion fight the Bull. But I can't trace these animals, and I don't
+believe it is worth while. The brightest stars in them everybody can see
+and admire--Sirius, the Bigger Dog, and Procyon, the Smaller Dog.
+
+Every one ought to know Sirius, because he is the brightest star of all.
+(Of course, he is not so bright as Venus and Jupiter, but they are
+planets.) To find him, draw a line from the eye of the Bull through the
+belt of Orion and extend it toward the southeast about twenty degrees.
+They call him the Dog star because he follows the heels of Orion. And
+people still call the hottest days of summer "dog days" because 400
+years before Christ the Romans noticed that the Dog star rose just
+before the sun at that time. The Romans thought he chased the sun across
+the sky all day and therefore was responsible for the great heat. But
+that was a foolish explanation. And so is the old notion that dogs are
+likely to go mad during the dog days "because the dog star is in the
+ascendant." So is the idea that Sirius is an unlucky star.
+
+There are no lucky or unlucky stars. These are all superstitions, and we
+ought to be ashamed to believe any superstition. Yet for thousands of
+years before we had public schools and learned to know better, people
+believed that every one was born under a lucky star or an unlucky one,
+and they believe that farmers ought to plant or not plant, according to
+the size of the moon. Now we know that is all bosh. Those old
+superstitions have done more harm than good. One of the most harmful was
+the belief in witches. Let us resolve never to be afraid of these old
+tales, but laugh at them.
+
+Why should anybody be afraid of anything so lovely as Sirius? I used to
+think Sirius twinkled more than any other star. But that was bad
+reasoning on my part. I might have noticed that every star twinkles more
+near the horizon than toward the zenith. I might have noticed that stars
+twinkle more on clear, frosty nights than when there is a little uniform
+haze. And putting those two facts together I might have reasoned that
+the stars never really twinkle at all; they only seem to. I might have
+concluded that the twinkling is all due to the atmosphere--that blanket
+of air which wraps the earth around. The nearer the earth, the thicker
+the air, and the more it interferes with the light that comes to us from
+the stars.
+
+They say that Sirius never looks exactly alike on two successive nights.
+"It has a hundred moods," says Mr. Serviss, "according to the state of
+the atmosphere. By turns it flames, it sparkles, it glows, it blazes, it
+flares, it flashes, it contracts to a point, and sometimes when the air
+is still, it burns with a steady white light." (Quotation somewhat
+altered and condensed.)
+
+It is a pity that so fine a star as Procyon should be called the
+"Smaller Dog," because it suffers unjustly by comparison with Sirius. If
+it were in some other part of the sky we might appreciate it more,
+because it is brighter than most of the fifteen first-magnitude stars we
+can see. My brother William has grown to love it, but perhaps that is
+because he always "sympathizes with the under dog." He was the youngest
+brother and knows. And curiously enough he was nicknamed "the dog"--just
+why, I don't know.
+
+To find Procyon, drawn a line from Sirius northeast about twenty
+degrees. And to make sure, draw one east from Betelgeuse about the same
+distance. These three stars make a triangle of which the sides are
+almost equal.
+
+The name Procyon means "before the dog" referring to the fact that you
+can see him fifteen or twenty minutes earlier every night than you can
+see Sirius.
+
+The only kind word about Procyon I have heard in recent years was in
+connection with that miserable business of Dr. Cook and the North Pole.
+A Captain Somebody-or-other was making observations for Dr. Cook, and he
+wanted to know what time it was. He had no watch and didn't want to
+disturb any one. So he looked out of the window and saw by the star
+Procyon that it was eleven o'clock.
+
+That sounds mysterious, but it is easy if you have a planisphere like
+ours. Last winter when we were all enjoying Orion, the Bull, and the two
+Dogs, I used to whirl the planisphere around to see where they would be
+at six o'clock at night, at eight, at ten, at midnight, and even at six
+o'clock in the morning. And so, if I waked up in the night I could tell
+what time it was without even turning my head. Sometimes I looked out of
+my window, saw Orion nearly overhead and knew it must be midnight. And
+sometimes I woke up just before daybreak and saw the great Bull backing
+down out of sight in the west, the mighty Hunter still brandishing his
+club, and his faithful Dogs following at his heels.
+
+
+
+
+SEVEN FAMOUS CONSTELLATIONS
+
+
+There are only seven more constellations that seem to me interesting
+enough for every one to know and love all his life. These are:
+
+  The Lion (Spring)
+
+  The Twins (Spring)
+
+  The Virgin (Summer)
+
+  The Herdsman (Summer)
+
+  The Northern Crown (Summer)
+
+  The Scorpion (Summer)
+
+  Southern Fish (Autumn)
+
+I have named the seasons when, according to some people, these
+constellations are most enjoyable. But these are not the only times when
+you can see them. (If you had that seventy-five-cent planisphere, now,
+you could always tell which constellations are visible and just where to
+find them.) No matter what time of year you read this chapter, it is
+worth while to go out and look for these marvels. You can't possibly
+miss them all.
+
+Have you ever seen a Sickle in the sky? It's a beauty, and whenever I
+have seen it it has been turned very conveniently for me, because I am
+left-handed. It is so easy to find that I am almost ashamed to tell. But
+if you need help, draw a line through the Pointers backward, away from
+the Pole star, about forty degrees, and it will come a little west of
+the Sickle. The Sickle is only part of the Lion--the head and the
+forequarters. Only fanciful map-makers can trace the rest of the Lion.
+The bright star at the end of the handle is Regulus, which means "king,"
+from the stupid old notion that this star ruled the lives of men. To
+this day people speak of the "Royal Star," meaning Regulus. And at the
+end of this chapter I will tell you about three other stars which the
+Persians called "royal stars."
+
+Another constellation which children particularly love is the
+Twins--Castor and Pollux. But the sailors got there first! For thousands
+of years the twins have been supposed to bring good luck to sailors. I
+don't believe a word of it. But I do know that sailors gloat over Castor
+and Pollux, and like them better than any other stars. The whole
+constellation includes all the stars east of the Bull and between the
+Charioteer and Procyon. But another way to outline the twins is to look
+northeast of Orion where you will see two rows of stars that run nearly
+parallel. To me the brothers seem to be standing, but all the old
+picture-makers show them sitting with their arms around each other, the
+two brightest stars being their eyes. The eyes are about five degrees
+apart--the same as the Pointers.
+
+Pollux is now brighter than Castor, but for thousands of years it was
+just the other way. It is only within three hundred years that this
+change has taken place. Whether Castor has faded or Pollux brightened,
+or both, I do not know. Anyhow, Castor is not quite bright enough to be
+a first magnitude star. Three hundred years is a short time in the
+history of man, and only a speck in the history of the stars. Three
+hundred years ago they killed people in Europe just because of the
+church they went to. That was why the Pilgrim Fathers sailed from
+England in 1620, and made the first permanent settlement in America,
+except, of course, Jamestown, Va., in 1607.
+
+There are plenty of stories about old Castor and Pollux, and, like all
+the other myths, they conflict, more or less. But all agree that these
+two brothers went with Jason in the ship Argo, shared his adventures and
+helped him get the golden fleece. And all agree that Castor and Pollux
+were "born fighters." And that is why the Roman soldiers looked up to
+these stars and prayed to them to help them win their battles.
+
+Now for the four summer constellations every one ought to know. The
+first thing to look for is two famous red or reddish stars--Arcturus and
+Antares.
+
+The way you find Arcturus is amusing. Look for the Big Dipper and find
+the star at the bottom of the dipper nearest the handle. Got it? Now
+draw a curve that will connect it with all the stars in the handle, and
+when you come to the end of the handle keep on till you come to the
+first very bright star--about twenty-five degrees. That is the monstrous
+star Arcturus, probably the biggest and swiftest star we can ever see
+with the naked eye in the northern hemisphere. He is several times as
+big as our sun, and his diameter is supposed to be several million
+miles. He is called a "runaway sun," because he is rushing through space
+at the rate of between two hundred and three hundred miles a second.
+That means between seventeen and thirty-four million miles a day!
+
+He is coming toward us, too! At such a rate you might think that
+Arcturus would have smashed the earth to pieces long ago. But he is
+still very far away, and there is no danger. Some people say that if Job
+were to come to life, the sky would seem just the same to him as it did
+3,400 years ago. The only difference he might notice would be in
+Arcturus. That would seem to him out of place by a distance about three
+times the apparent diameter of the moon.
+
+Some people believe this because Job said, "Canst thou guide Arcturus
+with his sons?" and therefore they imagine that he meant this red star.
+But I believe he meant the Big Dipper. For in King James's time, when
+the Bible was translated into English, the word "Arcturus" meant the Big
+Dipper or rather the Great Bear. And for centuries before it meant the
+Great Bear. One proof of it is that "Arcturus" comes from an old Greek
+word meaning "bear"--the same word from which we get arctic. It is only
+within a few hundred years that astronomers have agreed to call the
+Great Bear "Ursa Major," and this red star Arcturus. So I think all the
+books which say Job mentioned this red star are mistaken. I believe
+Webster's Dictionary is correct in this matter, and I believe the
+Revised Version translates Job's Hebrew phrase more correctly when it
+says, "Canst thou guide the Bear with her train?"
+
+Anyhow, Arcturus is a splendid star--the brightest in the constellation
+called the "Herdsman" or Booetes. It is not worth while to trace the
+Herdsman, but here is an interesting question. Is Arcturus really red?
+The books mostly say he is yellow. They say he looks red when he is low
+in the sky, and yellow when he is high. How does he look to you? More
+yellow than red?
+
+Well, there's no doubt about Antares being red. To find him, draw a long
+line from Regulus through Arcturus to Antares, Arcturus being more than
+half way between the other two. But if Regulus and the Sickle are not
+visible, draw a line from Altair, at right angles to the Eagle, until
+you come to a bright star about sixty degrees away. You can't miss
+Antares, for he is the only red star in that part of the sky.
+
+Antares belongs to a showy constellation called the Scorpion. I cannot
+trace all the outline of a spider-like creature, but his poisonous tail
+or "stinger" is made by a curved line of stars south and east of
+Antares. And you can make a pretty fan by joining Antares to several
+stars in a curve which are west of Antares and a little north. There is
+an old tale that this Scorpion is the one that stung Orion to death when
+he began to "show off" and boast that there was no animal in the world
+that could kill him.
+
+Another very bright star in the southern part of the sky is Spica. To
+find it, start with the handle of the Dipper, and making the same
+backward curve which helped you to find Arcturus, keep on till you come
+to the white star Spica--say thirty degrees beyond Arcturus. This is the
+brightest star in the constellation called "the Virgin." It is not worth
+while trying to trace her among nearly forty faint stars in this
+neighbourhood. But she is supposed to be a winged goddess who holds up
+in her right hand an _ear of wheat_, and that is what Spica means.
+
+Now for an autumn constellation--the Southern Fish. I don't care if you
+fail to outline a fish, but I do want you to see the bright star that is
+supposed to be in the fish's mouth. And I don't want you to balk at its
+hard name--Fomalhaut (pronounced _fo'-mal-o_). It is worth a lot of
+trouble to know it as a friend. To find it, you have to draw an
+exceedingly long line two-thirds of the way across the whole sky. Start
+with the Pointers. Draw a line through them and the Pole star and keep
+clear on until you come to a solitary bright star rather low down in the
+south. That is Fomalhaut. It looks lonely and is lonely, even when you
+look at it through a telescope.
+
+And now for the last story. Once upon a time the Persians thought there
+must be four stars that rule the lives of men. So they picked out one in
+the north and one in the south and one in the east and one in the west,
+just as if they were looking for four bright stars to mark the points of
+the compass. If you want to find them yourself without my help don't
+read the next sentence, but shut this book and go out and see. Then
+write down on a piece of paper the stars you have selected and compare
+them with the list I am about to give. Here are the four royal stars of
+the Persians: Fomalhaut for the north, Regulus for the south, Aldebaran
+for the east, and Antares for the west.
+
+Why doesn't this list agree with yours? Because Persia is so far south
+of where we live. Ah, there are very few things that are absolutely
+true. Let's remember that and not be too sure: for everything depends
+upon the point of view! I hope you will see Fomalhaut before Christmas,
+before he disappears in the west. He is with us only five months and is
+always low--near the horizon. But the other seven months in the year he
+gladdens the children of South America and the rest of the southern
+hemisphere, for they see him sweeping high and lonely far up into their
+sky and down again.
+
+But the loveliest of all the constellations described in this chapter is
+the Northern Crown. It is not a perfect crown--only about half a
+circle--but enough to suggest a complete ring. Look for it east of
+Arcturus. I can see seven or eight stars in the half-circle, one of
+which is brighter than all the others. That one is called "the Pearl."
+The whole constellation is only fifteen degrees long, but "fine things
+come in small packages"; and children grow to love the Northern Crown
+almost as much as they love the Pleiades.
+
+
+
+
+THE TWENTY BRIGHTEST STARS
+
+
+If you have seen everything I have described so far, you have reason to
+be happy. For now you know sixteen of the most famous constellations and
+fifteen of the twenty brightest stars. There are only twenty stars of
+the first magnitude. "Magnitude" ought to mean size, but it doesn't. It
+means brightness--or rather the apparent brightness--of the stars when
+seen by us. The word magnitude was used in the old days before
+telescopes, when people thought the brighter a star is the bigger it
+must be. Now we know that the nearer a star is to us the brighter it is,
+and the farther away the fainter. Some of the bright stars are
+comparatively near us, some are very far. Deneb and Canopus are so far
+away that it takes over three hundred years for their light to reach us.
+What whoppers they must be--many times as big as our sun.
+
+Here is a full list of the twenty stars of the first magnitude arranged
+in the order of their brightness. You will find this table very useful.
+
+ ----------------+---------------+-------------+--------------------------
+  Stars          | Pronounced    |Constellation|   Interesting facts
+ ----------------+---------------+-------------+--------------------------
+ Sirius          | _sir'i-us_    | Big Dog     | Brightest star. Nearest
+                 |               |             | star visible in Northern
+                 |               |             | hemisphere
+ Canopus*        | _ca-no'pus_   | Ship Argo   | Perhaps the largest body
+                 |               |             | in universe
+ Alpha Centauri* | _al'fa        |             |
+                 |  sen-taw're_  | Centaur     | Nearest star. Light four
+                 |               |             | years away
+ Vega            | _ve'ga_       | Lyre        | Brightest star in the
+                 |               |             | Northern sky. Bluish
+ Capella         | _ca-pell'a_   | Charioteer  | Rivals Vega, but opposite
+                 |               |             | the pole. Yellowish
+ Arcturus        | _ark-tu'rus_  | Herdsman    | Swiftest of the bright
+                 |               |             | stars. 200 miles a second
+ Rigel           | _re'jel_      | Orion       | Brightest star in Orion.
+                 |               |             | White star in left foot
+ Procyon         | _pro'si-on_   | Little Dog  | Before the dog. Rises a
+                 |               |             | little before Sirius
+ Achernar*       | _a-ker'nar_   | River Po    | Means the end of the river
+ Beta Centauri*  | _ba'ta        |             |
+                 |  sen-taw're_  | Centaur     | This and its mate point to
+                 |               |             | the Southern Cross
+ Altair          | _al-tare'_    | Eagle       | Helps you find Vega and
+                 |               |             | Northern Cross
+ Betelgeuse      | _bet-el-guz'_ | Orion       | Means "armpit." The red
+                 |               |             | star in the right shoulder
+ Alpha Crucis*   | _al'fa        | Southern    |
+                 |  cru'sis_     |  Cross      | At the base of the most
+                 |               |             | famous Southern
+                 |               |             | constellation
+ Aldebaran       | _al-deb'a-ran_| Bull        | The red eye in the V
+ Pollux          | _pol'lux_     | Twins       | Brighter than Castor
+ Spica           | _spi'ca_      | Virgin      | Means ear of wheat
+ Antares         | _an-ta'rez_   | Scorpion    | Red star. Name means
+                 |               |             | "looks like Mars"
+ Fomalhaut       | _fo'mal-o_    | Southern    |
+                 |               |  Fish       | The lonely star in the
+                 |               |             | Southern sky
+ Deneb           | _den'eb_      | Swan        | Top of Northern Cross,
+                 |               |             | or tail of Swan
+ Regulus         | _reg'u-lus_   | Lion        | The end of the handle
+                 |               |             | of the Sickle
+ ----------------+---------------+-------------+--------------------------
+
+The five stars marked * belong to the Southern hemisphere, and we can
+never see them unless we travel far south. Last winter I went to Florida
+and saw Canopus, but to see the Southern Cross you should cross the
+Tropic of Cancer.
+
+
+
+
+HOW TO LEARN MORE
+
+
+All I can hope to do in this book is to get you enthusiastic about
+astronomy. I don't mean "gushy." Look in the dictionary and you will
+find that the enthusiast is not the faddist. He is the one who sticks to
+a subject for a lifetime.
+
+Nor do I care a rap whether you become an astronomer--or even buy a
+telescope. There will be always astronomers coming on, but there are too
+few people who know and love even a few of the stars. I want you to make
+popular astronomy a life-long hobby. Perhaps you may have to drop it for
+ten or fifteen years. Never mind, you will take up the study again. I
+can't expect you to read a book on stars if you are fighting to make a
+living or support a family, unless it really rests you to read about the
+stars. It does rest me. When things go wrong at the office or at home, I
+can generally find rest and comfort from music. And if the sky is clear,
+I can look at the stars, and my cares suddenly seem small and drop away.
+
+Let me tell you why and how you can get the very best the stars have to
+teach you, without mathematics or telescope. Follow this programme and
+you need never be afraid of hard work, or of exhausting the pleasures
+of the subject. Go to your public library and get one of the books I
+recommend in this chapter, and read whatever interests you. I don't care
+whether you take up planets before comets or comets before planets, but
+whatever you do do it well. Soak the interesting facts right in. Nail
+them down. See everything the book talks about. Make notes of things to
+watch for. Get a little blank book and write down the date you first saw
+each thing of interest. Write down the names of the constellations you
+love most. Before you lay down any star book you are reading, jot down
+the most wonderful and inspiring thing you have read--even if you have
+only time to write a single word that may recall it all to you. Treasure
+that little note book as long as you live. Every year it will get more
+precious to you.
+
+Now for the books:
+
+1. _Martin._ _The Friendly Stars._ Harper & Brothers, New York, 1907.
+
+This book teaches you first the twenty brightest stars and then the
+constellations. I cannot say that this, or any other, is the "best
+book," but it has helped me most, and I suppose it is only natural that
+we should love best the first book that introduces us to a delightful
+subject.
+
+2. _Serviss._ _Astronomy with the Naked Eye._ Harper & Brothers, New
+York, 1908.
+
+This teaches you the constellations first and the brightest stars
+incidentally. Also it gives the old myths.
+
+3. _Serviss._ _Astronomy with an Opera-Glass._ D. Appleton & Co., New
+York, 1906.
+
+4. _Serviss._ _Pleasures of the Telescope._ D. Appleton & Co., New York,
+1905.
+
+5. _Milham._ _How to Identify the Stars._ The Macmillan Co., New York,
+1909.
+
+This gives a list of eighty-eight constellations, including thirty-six
+southern ones, and has tracings of twenty-eight.
+
+6. _Elson._ _Star Gazer's Handbook._ Sturgis & Walton Co., New York,
+1909.
+
+About the briefest and cheapest. Has good charts and makes a specialty
+of the myths.
+
+7. _Serviss._ _Curiosities of the Sky._ Harper & Brothers, New York.
+
+Tells about comets, asteroids, shooting stars, life on Mars, nebulae,
+temporary stars, coal-sacks, Milky Way, and other wonders.
+
+8. _Ball._ _Starland._ Ginn & Co., Boston, New York, etc., 1899.
+
+This tells about a great many interesting experiments in astronomy that
+children can make.
+
+       *       *       *       *       *
+
+If I had only a dollar or less to spend on astronomy I should buy a
+planisphere. I got mine from Thomas Whittaker, No. 2 Bible House, New
+York. It cost seventy-five cents, and will tell you where to find any
+star at any time in the year. It does not show the planets, however. A
+planisphere that will show the planets costs about five dollars.
+However, there are only two very showy planets, viz., Venus and Jupiter.
+Any almanac will tell you (for nothing) when each of these is morning
+star, and when each of them is evening star.
+
+The best newspaper about stars, as far as I know, is a magazine called
+_The Monthly Evening Sky Map_, published by Leon Barritt, 150 Nassau
+St., New York. It costs a dollar a year. It gives a chart every month,
+showing all the planets, and all the constellations. Also it tells you
+about the interesting things, like comets, before they come.
+
+Good-bye. I hope you will never cease to learn about and love the earth
+and the sky. Perhaps you think you have learned a great deal already.
+But your pleasures have only begun. Wait till you learn about how the
+world began, the sun and all his planets, the distances between the
+stars, and the millions of blazing suns amid the Milky Way!
+
+
+THE END
+
+[Illustration: THE SKY IN WINTER]
+
+NOTE.--These simplified star maps are not as accurate as a planisphere,
+but they may be easier for children. All star maps are like ordinary
+maps, except that east and west are transposed. The reason for this is
+that you can hold a star map over your head, with the pole star toward
+the north, and the map will then match the sky. These maps contain some
+constellations that are only for grown-ups to study. The Winter
+constellations every child should know are:
+
+  AURIGA, the Charioteer
+  CANIS MAJOR, the Big Dog
+  CANIS MINOR, the Little Dog
+  CASSIOPEIA, the Queen in Her Chair
+  CYGNUS, the Swan
+  LEO, the Lion
+  ORION, the Hunter
+  PERSEUS, Which Has the Arc
+  TAURUS, the Bull
+  URSA MAJOR, the Great Bear
+  URSA MINOR, the Little Bear
+
+[Illustration: THE SKY IN SPRING]
+
+NOTE.--Once upon a time all the educated people spoke Latin. It was the
+nearest approach to a universal language. So most of the constellations
+have Latin names. The English, French and German names are all
+different, but if all children would learn the Latin names they could
+understand one another. The Spring constellations every child should
+know are:
+
+  LEO, the Lion
+  LYRA, the Lyre
+  CASSIOPEIA, the Queen in her Chair
+  SCORPIO, the Scorpion
+  URSA MAJOR, the Great Bear
+  URSA MINOR, the Little Bear
+  VIRGO, the Virgin
+
+[Illustration: THE SKY IN SUMMER]
+
+NOTE.--Every sky map is good for three months, in this way: If this is
+correct on June 1st at 10 P.M., it will be correct July 1st at 8 P.M.,
+and August 1st at 6 P.M. This is because the stars rise four minutes
+earlier every night. Thus, after thirty days, any star will rise thirty
+times four minutes earlier, or 120 minutes, or two hours. Children need
+not learn all the Summer constellations. The most interesting are:
+
+  AURIGA, the Charioteer
+  CANIS MAJOR, the Big Dog
+  CYGNUS, the Swan
+  LYRA, the Lyre
+  SCORPIO, the Scorpion
+
+[Illustration: THE SKY IN AUTUMN]
+
+NOTE.--This book tells how to find all the most interesting stars and
+constellations without maps, but many people prefer them. How to use
+star maps is explained under "The Sky in Winter." The Autumn
+constellations most interesting to children are:
+
+  AQUILA, the Eagle
+  AURIGA, the Charioteer
+  CASSIOPEIA, the Queen in Her Chair
+  CYGNUS, the Swan
+  LYRA, the Lyre
+  PERSEUS, Which Has the Arc
+  TAURUS, the Bull
+  URSA MAJOR, the Great Bear
+  URSA MINOR, the Little Bear
+
+
+Transcriber's notes
+
+  Page 124 "streams, runing" corrected to "streams, running"
+  Page 127 "where he globe" corrected to "where the globe"
+  Page 138 "ceatures to prove" corrected to "creatures to prove"
+  Page 216 "this consellation is" corrected to "this constellation is"
+  Page 203 "Everybirth day" corrected to "Every birthday"
+
+
+
+
+
+
+
+End of the Project Gutenberg EBook of Earth and Sky Every Child Should Know, by
+Julia Ellen Rogers
+
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