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diff --git a/old/68326-0.txt b/old/68326-0.txt deleted file mode 100644 index b82fc85..0000000 --- a/old/68326-0.txt +++ /dev/null @@ -1,3848 +0,0 @@ -The Project Gutenberg eBook of History of electric light, by Henry -Schroeder - -This eBook is for the use of anyone anywhere in the United States and -most other parts of the world 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. If you are not located in the United States, you -will have to check the laws of the country where you are located before -using this eBook. - -Title: History of electric light - -Author: Henry Schroeder - -Release Date: June 16, 2022 [eBook #68326] - -Language: English - -Produced by: Charlene Taylor, Charlie Howard, and the Online Distributed - Proofreading Team at https://www.pgdp.net (This file was - produced from images generously made available by The - Internet Archive/American Libraries.) - -*** START OF THE PROJECT GUTENBERG EBOOK HISTORY OF ELECTRIC -LIGHT *** - - - - - -Transcriber’s Notes - - -In this Plain Text version of this eBook, italics are enclosed within -~tildas~, superscripts and subscripts are enclosed in curly braces and -preceded by a caret ^{superscript} or an underscore _{subscript}. - -Other notes will be found at the end of this eBook. - - - - - SMITHSONIAN MISCELLANEOUS COLLECTIONS - VOLUME 76, NUMBER 2 - - - HISTORY OF ELECTRIC LIGHT - - - BY - HENRY SCHROEDER - Harrison, New Jersey - - [Illustration: FOR THE INCREASE - AND DIFFVSION OF - KNOWLEDGE AMONG MEN - - SMITHSONIAN - INSTITVTION - WASHINGTON 1846] - - (PUBLICATION 2717) - - - CITY OF WASHINGTON - PUBLISHED BY THE SMITHSONIAN INSTITUTION - AUGUST 15, 1923 - - - - - The Lord Baltimore Press - BALTIMORE, MD., U. S. A. - - - - -CONTENTS - - - PAGE - - List of Illustrations v - - Foreword ix - - Chronology of Electric Light xi - - Early Records of Electricity and Magnetism 1 - - Machines Generating Electricity by Friction 2 - - The Leyden Jar 3 - - Electricity Generated by Chemical Means 3 - - Improvement of Volta’s Battery 5 - - Davy’s Discoveries 5 - - Researches of Oersted, Ampère, Schweigger and Sturgeon 6 - - Ohm’s Law 7 - - Invention of the Dynamo 7 - - Daniell’s Battery 10 - - Grove’s Battery 11 - - Grove’s Demonstration of Incandescent Lighting 12 - - Grenet Battery 13 - - De Moleyns’ Incandescent Lamp 13 - - Early Developments of the Arc Lamp 14 - - Joule’s Law 16 - - Starr’s Incandescent Lamp 17 - - Other Early Incandescent Lamps 19 - - Further Arc Lamp Developments 20 - - Development of the Dynamo, 1840–1860 24 - - The First Commercial Installation of an Electric Light 25 - - Further Dynamo Developments 27 - - Russian Incandescent Lamp Inventors 30 - - The Jablochkoff “Candle” 31 - - Commercial Introduction of the Differentially Controlled Arc Lamp 33 - - Arc Lighting in the United States 33 - - Other American Arc Light Systems 40 - - “Sub-Dividing the Electric Light” 42 - - Edison’s Invention of a Practical Incandescent Lamp 43 - - Edison’s Three-Wire System 53 - - Development of the Alternating Current Constant Potential System 54 - - Incandescent Lamp Developments, 1884–1894 56 - - The Edison “Municipal” Street Lighting System 62 - - The Shunt Box System for Series Incandescent Lamps 64 - - The Enclosed Arc Lamp 65 - - The Flame Arc Lamp 67 - - The Constant Current Transformer for Series Circuits 69 - - Enclosed Series Alternating Current Arc Lamps 69 - - Series Incandescent Lamps on Constant Current Transformers 70 - - The Nernst Lamp 71 - - The Cooper-Hewitt Lamp 72 - - The Luminous or Magnetite Arc Lamp 74 - - Mercury Arc Rectifier for Magnetite Arc Lamps 77 - - Incandescent Lamp Developments, 1894–1904 78 - - The Moore Tube Light 79 - - The Osmium Lamp 82 - - The Gem Lamp 82 - - The Tantalum Lamp 84 - - Invention of the Tungsten Lamp 85 - - Drawn Tungsten Wire 87 - - The Quartz Mercury Vapor Arc Lamp 88 - - The Gas-Filled Tungsten Lamp 89 - - Types and Sizes of Tungsten Lamps Now Made 91 - - Standard Voltages 93 - - Cost of Incandescent Electric Light 93 - - Statistics Regarding the Present Demand for Lamps 94 - - Selected Bibliography 95 - - - - -LIST OF ILLUSTRATIONS - - - PAGE - - Portion of the Electrical Exhibit in the United States National - Museum viii - - Otto Von Guericke’s Electric Machine, 1650 2 - - Voltaic Pile, 1799 4 - - Faraday’s Dynamo, 1831 8 - - Pixii’s Dynamo, 1832 9 - - Daniell’s Cell, 1836 10 - - Grove’s Cell, 1838 11 - - Grove’s Incandescent Lamp, 1840 13 - - De Moleyns’ Incandescent Lamp, 1841 14 - - Wright’s Arc Lamp, 1845 15 - - Archereau’s Arc Lamp, 1848 16 - - Starr’s Incandescent Lamp, 1845 18 - - Staite’s Incandescent Lamp, 1848 19 - - Roberts’ Incandescent Lamp, 1852 19 - - Farmer’s Incandescent Lamp, 1859 20 - - Roberts’ Arc Lamp, 1852 21 - - Slater and Watson’s Arc Lamp, 1852 21 - - Diagram of “Differential” Method of Control of an Arc Lamp 22 - - Lacassagne and Thiers’ Differentially Controlled Arc Lamp, 1856 23 - - Serrin’s Arc Lamp, 1857 24 - - Siemens’ Dynamo, 1856 25 - - Alliance Dynamo, 1862 26 - - Wheatstone’s Self-Excited Dynamo, 1866 27 - - Gramme’s Dynamo, 1871 28 - - Gramme’s “Ring” Armature 28 - - Alteneck’s Dynamo with “Drum” Wound Armature, 1872 29 - - Lodyguine’s Incandescent Lamp, 1872 30 - - Konn’s Incandescent Lamp, 1875 30 - - Bouliguine’s Incandescent Lamp, 1876 31 - - Jablochkoff “Candle,” 1876 32 - - Jablochkoff’s Alternating Current Dynamo, 1876 33 - - Wallace-Farmer Arc Lamp, 1875 34 - - Wallace-Farmer Dynamo, 1875 34 - - Weston’s Arc Lamp, 1876 35 - - Brush’s Dynamo, 1877 36 - - Diagram of Brush Armature 36 - - Brush’s Arc Lamp, 1877 37 - - Thomson-Houston Arc Dynamo, 1878 38 - - Diagram of T-H Arc Lighting System 39 - - Thomson-Houston Arc Lamp, 1878 40 - - Thomson Double Carbon Arc Lamp 40 - - Maxim Dynamo 41 - - Sawyer’s Incandescent Lamp, 1878 42 - - Farmer’s Incandescent Lamp, 1878 42 - - Maxim’s Incandescent Lamp, 1878 43 - - Edison’s First Experimental Lamp, 1878 44 - - Diagram of Constant Current Series System 45 - - Diagram of Edison’s Multiple System, 1879 45 - - Edison Dynamo, 1879 46 - - Edison’s High Resistance Platinum Lamp, 1879 47 - - Edison’s High Resistance Platinum in Vacuum Lamp, 1879 47 - - Edison’s Carbon Lamp of October 21, 1879 48 - - Demonstration of Edison’s Incandescent Lighting System 49 - - Dynamo Room, S. S. Columbia 50 - - Original Socket for Incandescent Lamps 51 - - Wire Terminal Base Lamp, 1880 51 - - Original Screw Base Lamp, 1880 52 - - Improved Screw Base Lamp, 1881 52 - - Final Form of Screw Base, 1881 53 - - Diagram of Edison’s Three Wire System, 1881 54 - - Diagram of Stanley’s Alternating Current Multiple System, 1885 55 - - Standard Edison Lamp, 1884 56 - - Standard Edison Lamp, 1888 56 - - Standard Edison Lamp, 1894 57 - - Various Bases in Use, 1892 58 - - Thomson-Houston Socket 59 - - Westinghouse Socket 59 - - Adapters for Edison Screw Sockets, 1892 60 - - Various Series Bases in Use, 1892 61 - - Edison “Municipal” System, 1885 62 - - Edison “Municipal” Lamp, 1885 63 - - Shunt Box System, 1887 64 - - Enclosed Arc Lamp, 1893 65 - - Open Flame Arc Lamp, 1898 66 - - Enclosed Flame Arc Lamp, 1908 66 - - Constant Current Transformer, 1900 68 - - Series Incandescent Lamp Socket with Film Cutout, 1900 70 - - Nernst Lamp, 1900 71 - - Diagram of Nernst Lamp 72 - - Cooper-Hewitt Mercury Vapor Arc Lamp, 1901 73 - - Diagram of Cooper-Hewitt Lamp for Use on Alternating Current 74 - - Luminous or Magnetite Arc Lamp, 1902 75 - - Diagram of Series Magnetite Arc Lamp 76 - - Mercury Arc Rectifier Tube for Series Magnetite Arc Circuits, 1902 77 - - Early Mercury Arc Rectifier Installation 78 - - The Moore Tube Light, 1904 79 - - Diagram of Feeder Valve of Moore Tube 80 - - Osmium Lamp, 1905 82 - - Gem Lamp, 1905 83 - - Tantalum Lamp, 1906 84 - - Tungsten Lamp, 1907 86 - - Drawn Tungsten Wire Lamp, 1911 87 - - Quartz Mercury Vapor Lamp, 1912 88 - - Gas Filled Tungsten Lamp, 1913 89 - - Gas Filled Tungsten Lamp, 1923 90 - - Standard Tungsten Lamps, 1923 92 - - -[Illustration: PORTION OF THE ELECTRICAL EXHIBIT IN THE UNITED STATES -NATIONAL MUSEUM. - -Section devoted to the historical development of the electric light and -dynamo.] - - - - -FOREWORD - - -In the year 1884 a Section of Transportation was organized in the -United States National Museum for the purpose of preparing and -assembling educational exhibits of a few objects of railroad machinery -which had been obtained both from the Centennial Exhibition held in -Philadelphia in 1876 and still earlier as incidentals to ethnological -collections, and to secure other collections relating to the railway -industry. - -From this beginning the section was expanded to include the whole -field of engineering and is designated at present as the Divisions of -Mineral and Mechanical Technology. The growth and enlargement of the -collections has been particularly marked in the fields of mining and -mineral industries; mechanical engineering, especially pertaining to -the steam engine, internal combustion engine and locomotive; naval -architecture, and electrical engineering, particularly the development -of the telegraph, telephone and the electric light. - -In the acquisition of objects visualizing the history of electric -light the Museum has been rather fortunate, particularly as regards -the developments in the United States. Thus mention may be made of -the original Patent Office models of the more important dynamos, arc -lights and incandescent lights, together with original commercial -apparatus after these models; a unit of the equipment used in the -first commercially successful installation on land of an incandescent -lighting system, presented by Joseph E. Hinds in whose engraving -establishment in New York City the installation was made in 1881; and -a large series of incandescent lights, mainly originals, visualizing -chronologically the developments of the Edison light from its -inception, presented at intervals since the year 1898 by the General -Electric Company. - -The object of all collections in the Divisions is to visualize -broadly the steps by which advances have been made in each field of -engineering; to show the layman the fundamental and general principles -which are the basis for the developments; and to familiarize the -engineer with branches of engineering other than his own. Normally -when a subject is completely covered by a collection of objects, a -paper is prepared and published describing the collection and the -story it portrays. In the present instance, however, on account of -the uncertainty of the time of completing the collection, if it is -possible ever to bring this about, it was thought advisable to publish -Mr. Schroeder’s paper which draws upon the Museum collection as -completely as possible. - - CARL W. MITMAN, - ~Curator, Divisions of Mineral and - Mechanical Technology, - U. S. National Museum~. - - - - -CHRONOLOGY OF ELECTRIC LIGHT - - - 1800--Allesandro Volta demonstrated his discovery that electricity - can be generated by chemical means. The VOLT, the unit of - electric pressure, is named in his honor for this discovery - of the electric battery. - - 1802--Sir Humphry Davy demonstrated that electric current can heat - carbon and strips of metal to incandescence and give light. - - 1809--Sir Humphry Davy demonstrated that current will give a - brilliant flame between the ends of two carbon pencils - which are first allowed to touch each other and then pulled - apart. This light he called the “arc” on account of its - arch shape. - - 1820--André Marie Ampère discovered that current flowing through - a coiled wire gives it the properties of a magnet. The - AMPERE, the unit of flow of electric current, is named in - his honor for this discovery. - - 1825--Georg Simon Ohm discovered the relation between the voltage, - ampereage and resistance in an electric circuit, which is - called Ohm’s Law. The OHM, the unit of electric resistance, - is named in his honor for this discovery. - - 1831--Michael Faraday discovered that electricity can be generated - by moving a wire in the neighborhood of a magnet, the - principle of the dynamo. - - 1840--Sir William Robert Grove demonstrated his experimental - incandescent lamp in which platinum is made incandescent by - current flowing through it. - - 1841--Frederick De Moleyns obtained the first patent on an - incandescent lamp. The burner was powdered charcoal - operating in an exhausted glass globe. - - 1845--Thomas Wright obtained the first patent on an arc light. - - 1845--J. W. Starr invented an incandescent lamp consisting of a - carbon pencil operating in the vacuum above a column of - mercury. - - 1856--Joseph Lacassagne and Henry Thiers invented the - “differential” method of control of the arc which was - universally used twenty years later when the arc lamp was - commercially established. - - 1862--The first commercial installation of an electric light. An - arc light was put in a lighthouse in England. - - 1866--Sir Charles Wheatstone invented the “self-excited” dynamo, - now universally used. - - 1872--Lodyguine invented an incandescent lamp having a graphite - burner operating in nitrogen gas. - - 1876--Paul Jablochkoff invented the “electric candle,” an arc light - commercially used for lighting the boulevards in Paris. - - 1877–8--Arc light systems commercially established in the United - States by William Wallace and Prof. Moses Farmer, Edward - Weston, Charles F. Brush and Prof. Elihu Thomson and Edwin - J. Houston. - - 1879--Thomas Alva Edison invented an incandescent lamp consisting - of a high resistance carbon filament operating in a - high vacuum maintained by an all glass globe. These - principles are used in all incandescent lamps made today. - He also invented a completely new system of distributing - electricity at constant pressure, now universally used. - - 1882--Lucien Goulard and John D. Gibbs invented a series - alternating current system of distributing electric - current. This has not been commercially used. - - 1886--William Stanley invented a constant pressure alternating - current system of distribution. This is universally used - where current is to be distributed long distances. - - 1893--Louis B. Marks invented the enclosed carbon arc lamp. - - 1898--Bremer’s invention of the flame arc lamp, having carbons - impregnated with various salts, commercially established. - - 1900--Dr. Walther Nernst’s invention of the Nernst lamp - commercially established. The burner consisted of various - oxides, such as zirconia, which operated in the open air. - - 1901--Dr. Peter Cooper Hewitt’s invention of the mercury arc light - commercially established. - - 1902--The magnetite arc lamp was developed by C. A. B. Halvorson, - Jr. This has a new method of control of the arc. The - negative electrode consists of a mixture of magnetite and - other substances packed in an iron tube. - - 1904--D. McFarlan Moore’s invention of the Moore vacuum tube light - commercially established. This consisted of a long tube, - made in lengths up to 200 feet, from which the air had been - exhausted to about a thousandth of an atmosphere. High - voltage current passing through this rarefied atmosphere - caused it to glow. Rarefied carbon dioxide gas was later - used. - - 1905--Dr. Auer von Welsbach’s invention of the osmium incandescent - lamp commercially established, but only on a small scale - in Europe. The metal osmium, used for the filament which - operated in vacuum, is rarer and more expensive than - platinum. - - 1905--Dr. Willis R. Whitney’s invention of the Gem incandescent - lamp commercially established. The carbon filament had been - heated to a very high temperature in an electric resistance - furnace invented by him. The lamp was 25 per cent more - efficient than the regular carbon lamp. - - 1906--Dr. Werner von Bolton’s invention of the tantalum - incandescent lamp commercially established. - - 1907--Alexander Just and Franz Hanaman’s invention of the tungsten - filament incandescent lamp commercially established. - - 1911--Dr. William D. Coolidge’s invention of drawn tungsten wire - commercially established. - - 1913--Dr. Irving Langmuir’s invention of the gas-filled tungsten - filament incandescent lamp commercially established. - - - - - HISTORY OF ELECTRIC LIGHT - - BY HENRY SCHROEDER, - HARRISON, NEW JERSEY. - - - - -EARLY RECORDS OF ELECTRICITY AND MAGNETISM - - -About twenty-five centuries ago, Thales, a Greek philosopher, recorded -the fact that if amber is rubbed it will attract light objects. -The Greeks called amber “elektron,” from which we get the word -“electricity.” About two hundred and fifty years later, Aristotle, -another Greek philosopher, mentioned that the lodestone would attract -iron. Lodestone is an iron ore (Fe_{3}O_{4}), having magnetic qualities -and is now called magnetite. The word “magnet” comes from the fact that -the best specimens of lodestones came from Magnesia, a city in Asia -Minor. Plutarch, a Greek biographer, wrote about 100 A. D., that iron -is sometimes attracted and at other times repelled by a lodestone. This -indicates that the piece of iron was magnetised by the lodestone. - -In 1180, Alexander Neckham, an English Monk, described the compass, -which probably had been invented by sailors of the northern countries -of Europe, although its invention has been credited to the Chinese. -Early compasses probably consisted of an iron needle, magnetised by -a lodestone, mounted on a piece of wood floating in water. The word -lodestone or “leading stone” comes from the fact that it would point -towards the north if suspended like a compass. - -William Gilbert, physician to Queen Elizabeth of England, wrote a -book about the year 1600 giving all the information then known on -the subject. He also described his experiments, showing, among other -things, the existence of magnetic lines of force and of north and south -poles in a magnet. Robert Norman had discovered a few years previously -that a compass needle mounted on a horizontal axis would dip downward. -Gilbert cut a large lodestone into a sphere, and observed that the -needle did not dip at the equator of this sphere, the dip increasing -to 90 degrees as the poles were approached. From this he deduced that -the earth was a magnet with the magnetic north pole at the geographic -north pole. It has since been determined that these two poles do not -coincide. Gilbert suggested the use of the dipping needle to determine -latitude. He also discovered that other substances, beside amber, would -attract light objects if rubbed. - - - - -MACHINES GENERATING ELECTRICITY BY FRICTION - - -Otto Von Guericke was mayor of the city of Magdeburg as well as a -philosopher. About 1650 he made a machine consisting of a ball of -sulphur mounted on a shaft which could be rotated. Electricity was -generated when the hand was pressed against the globe as it rotated. -He also discovered that electricity could be conducted away from the -globe by a chain and would appear at the other end of the chain. Von -Guericke also invented the vacuum air pump. In 1709, Francis Hawksbee, -an Englishman, made a similar machine, using a hollow glass globe which -could be exhausted. The exhausted globe when rotated at high speed and -rubbed by hand would produce a glowing light. This “electric light” as -it was called, created great excitement when it was shown before the -Royal Society, a gathering of scientists, in London. - -[Illustration: OTTO VON GUERICKE’S ELECTRIC MACHINE, 1650. - -A ball of sulphur was rotated, electricity being generated when it -rubbed against the hand.] - -Stephen Gray, twenty years later, showed the Royal Society that -electricity could be conducted about a thousand feet by a hemp thread, -supported by silk threads. If metal supports were used, this could not -be done. Charles du Fay, a Frenchman, repeated Gray’s experiments, -and showed in 1733 that the substances which were insulators, and -which Gilbert had discovered, would become electrified if rubbed. -Those substances which Gilbert could not electrify were conductors of -electricity. - - - - -THE LEYDEN JAR - - -The thought came to Von Kleist, Bishop of Pomerania, Germany, about -1745, that electricity could be stored. The frictional machines -generated so small an amount of electricity (though, as is now known, -at a very high pressure--several thousand volts) that he thought he -could increase the quantity by storing it. Knowing that glass was -an insulator and water a conductor, he filled a glass bottle partly -full of water with a nail in the cork to connect the machine with the -water. Holding the bottle in one hand and turning the machine with -the other for a few minutes, he then disconnected the bottle from the -machine. When he touched the nail with his other hand he received a -shock which nearly stunned him. This was called the Leyden jar, the -forerunner of the present condenser. It received its name from the fact -that its discovery was also made a short time after by experimenters -in the University of Leyden. Further experiments showed that the hand -holding the bottle was as essential as the water inside, so these were -substituted by tin foil coatings inside and outside the bottle. - -Benjamin Franklin, American statesman, scientist and printer, made -numerous experiments with the Leyden jar. He connected several jars -in parallel, as he called it, which gave a discharge strong enough to -kill a turkey. He also connected the jars in series, or “in cascade” as -he called it, thus establishing the principle of parallel and series -connections. Noticing the similarity between the electric spark and -lightning, Franklin in 1752, performed his famous kite experiment. -Flying a kite in a thunderstorm, he drew electricity from the clouds to -charge Leyden jars, which were later discharged, proving that lightning -and electricity were the same. This led him to invent the lightning rod. - - - - -ELECTRICITY GENERATED BY CHEMICAL MEANS - - -Luigi Galvani was an Italian scientist. About 1785, so the story goes, -his wife was in delicate health, and some frog legs were being skinned -to make her a nourishing soup. An assistant holding the legs with a -metal clamp and cutting the skin with a scalpel, happened to let the -clamp and scalpel touch each other. To his amazement the frog legs -twitched. Galvani repeated the experiment many times by touching -the nerve with a metal rod and the muscle with a different metal rod -and allowing the rods to touch, and propounded the theory of animal -electricity in a paper he published in 1791. - -Allesandro Volta, a professor of physics in the University of Pavia, -Italy, read about Galvani’s work and repeated his experiments. He -found that the extent of the movement of the frog legs depended on the -metals used for the rods, and thus believed that the electric charge -was produced by the contact of dissimilar metals with the moisture in -the muscles. To prove his point he made a pile of silver and zinc discs -with cloths, wet with salt water, between them. This was in 1799, and -he described his pile in March, 1800, in a letter to the Royal Society -in London. - -[Illustration: VOLTAIC PILE, 1799. - -Volta discovered that electricity could be generated by chemical means -and made a pile of silver and zinc discs with cloths, wet with salt -water, between them. This was the forerunner of the present-day dry -battery. Photograph courtesy Prof. Chas. F. Chandler Museum, Columbia -University, New York.] - -This was an epoch-making discovery as it was the forerunner of the -present-day primary battery. Volta soon found that the generation of -electricity became weaker as the cloths became dry, so to overcome -this he made his “crown of cups.” This consisted of a series of cups -containing salt water in which strips of silver and zinc were dipped. -Each strip of silver in one cup was connected to the zinc strip in -the next cup, the end strips of silver and zinc being terminals of -the battery. This was the first time that a continuous supply of -electricity in reasonable quantities was made available, so the VOLT, -the unit of electrical pressure was named in his honor. It was later -shown that the chemical affinity of one of the metals in the liquid was -converted into electric energy. The chemical action of Volta’s battery -is that the salt water attacks the zinc when the circuit is closed -forming zinc chloride, caustic soda and hydrogen gas. The chemical -equation is: - - Zn + 2NaCl + 2H_{2}O = ZnCl_{2} + 2NaOH + H_{2} - - - - -IMPROVEMENT OF VOLTA’S BATTERY - - -It was early suggested that sheets of silver and zinc be soldered -together back to back and that a trough be divided into cells by these -bimetal sheets being put into grooves cut in the sides and bottom of -the trough. This is the reason why one unit of a battery is called a -“cell.” It was soon found that a more powerful cell could be made if -copper, zinc and dilute sulphuric acid were used. The zinc is dissolved -by the acid forming zinc sulphate and hydrogen gas, thus: - - Zn + H_{2}SO_{4} = ZnSO_{4} + H_{2} - -The hydrogen gas appears as bubbles on the copper and reduces the open -circuit voltage (about 0.8 volt per cell) as current is taken from the -battery. This is called “polarization.” Owing to minute impurities in -the zinc, it is attacked by the acid even when no current is taken from -the battery, the impurities forming with the zinc a short circuited -local cell. This is called “local action,” and this difficulty was at -first overcome by removing the zinc from the acid when the battery was -not in use. - - - - -DAVY’S DISCOVERIES - - -Sir Humphry Davy was a well-known English chemist, and with the aid of -powerful batteries constructed for the Royal Institution in London, -he made numerous experiments on the chemical effects of electricity. -He decomposed a number of substances and discovered the elements -boron, potassium and sodium. He heated strips of various metals to -incandescence by passing current through them, and showed that platinum -would stay incandescent for some time without oxidizing. This was about -1802. - -In the early frictional machines, the presence of electricity was shown -by the fact that sparks could be obtained. Similarly the breaking -of the circuit of a battery would give a spark. Davy, about 1809, -demonstrated that this spark could be maintained for a long time with -the large battery of 2000 cells he had had constructed. Using two -sticks of charcoal connected by wires to the terminals of this very -powerful battery, he demonstrated before the Royal Society the light -produced by touching the sticks together and then holding them apart -horizontally about three inches. The brilliant flame obtained he called -an “arc” because of its arch shape, the heated gases, rising, assuming -this form. Davy was given the degree of LL. D. for his distinguished -research work, and was knighted on the eve of his marriage, April 11, -1812. - - - - -RESEARCHES OF OERSTED, AMPÈRE, SCHWEIGGER AND STURGEON - - -Hans Christian Oersted was a professor of physics at the University of -Copenhagen in Denmark. One day in 1819, while addressing his students, -he happened to hold a wire, through which current was flowing, over -a large compass. To his surprise he saw the compass was deflected -from its true position. He promptly made a number of experiments and -discovered that by reversing the current the compass was deflected in -the opposite direction. Oersted announced his discovery in 1820. - -André Marie Ampère was a professor of mathematics in the Ecole -Polytechnic in Paris. Hearing of Oersted’s discovery, he immediately -made some experiments and made the further discovery in 1820 that if -the wire is coiled and current passed through it, the coil had all the -properties of a magnet. - -These two discoveries led to the invention of Schweigger in 1820, -of the galvanometer (or “multiplier” as it was then called), a very -sensitive instrument for measuring electric currents. It consisted of -a delicate compass needle suspended in a coil of many turns of wire. -Current in the coil deflected the needle, the direction and amount of -deflection indicating the direction and strength of the current. Ampère -further made the discovery that currents in opposite directions repel -and in the same directions attract each other. He also gave a rule -for determining the direction of the current by the deflection of the -compass needle. He developed the theory that magnetism is caused by -electricity flowing around the circumference of the body magnetised. -The AMPERE, the unit of flow of electric current, was named in honor of -his discoveries. - -In 1825 it was shown by Sturgeon that if a bar of iron were placed in -the coil, its magnetic strength would be very greatly increased, which -he called an electro-magnet. - - - - -OHM’S LAW - - -Georg Simon Ohm was born in Bavaria, the oldest son of a poor -blacksmith. With the aid of friends he went to college and became a -teacher. It had been shown that the rate of transfer of heat from one -end to the other of a metal bar is proportional to the difference -of temperature between the ends. About 1825, Ohm, by analogy and -experiment, found that the current in a conductor is proportional to -the difference of electric pressure (voltage) between its ends. He -further showed that with a given difference of voltage, the current -in different conductors is inversely proportional to the resistance -of the conductor. Ohm therefore propounded the law that the current -flowing in a circuit is equal to the voltage on that circuit divided by -the resistance of the circuit. In honor of this discovery, the unit of -electrical resistance is called the OHM. This law is usually expressed -as: - - C = E/R - -“C” meaning current (in amperes), “E” meaning electromotive force or -voltage (in volts) and “R” meaning resistance (in ohms). - -This is one of the fundamental laws of electricity and if thoroughly -understood, will solve many electrical problems. Thus, if any two of -the above units are known, the third can be determined. Examples: An -incandescent lamp on a 120-volt circuit consumes 0.4 ampere, hence its -resistance under such conditions is 300 ohms. Several trolley cars at -the end of a line take 100 amperes to run them and the resistance of -the overhead wire from the power house to the trolley cars is half -an ohm; the drop in voltage on the line between the power house and -trolley cars is therefore 50 volts, so that if the voltage at the power -house were 600, it would be 550 volts at the end of the line. - -Critics derided Ohm’s law so that he was forced out of his position -as teacher in the High School in Cologne. Finally after ten years Ohm -began to find supporters and in 1841 his law was publicly recognized by -the Royal Society of London which presented him with the Copley medal. - - - - -INVENTION OF THE DYNAMO - - -Michael Faraday was an English scientist. Born of parents in poor -circumstances, he became a bookbinder and studied books on electricity -and chemistry. He finally obtained a position as laboratory assistant -to Sir Humphry Davy helping him with his lectures and experiments. He -also made a number of experiments himself and succeeded in liquifying -chlorine gas for which he was elected to a Fellowship in the Royal -Institution in 1824. Following up Oersted’s and Ampère’s work, he -endeavored to find the relation between electricity and magnetism. -Finally on Oct. 17, 1831, he made the experiment of moving a permanent -bar magnet in and out of a coil of wire connected to a galvanometer. -This generated electricity in the coil which deflected the galvanometer -needle. A few days after, Oct. 28, 1831, he mounted a copper disk -on a shaft so that the disk could be rotated between the poles of -a permanent horseshoe magnet. The shaft and edge of the disk were -connected by brushes and wires to a galvanometer, the needle of which -was deflected as the disk was rotated. A paper on his invention was -read before the Royal Society on November 24, 1831, which appeared in -printed form in January, 1832. - -[Illustration: FARADAY’S DYNAMO, 1831. - -Faraday discovered that electricity could be generated by means of a -permanent magnet. This principle is used in all dynamos.] - -Faraday did not develop his invention any further, being satisfied, -as in all his work, in pure research. His was a notable invention but -it remained for others to make it practicable. Hippolyte Pixii, a -Frenchman, made a dynamo in 1832 consisting of a permanent horseshoe -magnet which could be rotated between two wire bobbins mounted on a -soft iron core. The wires from the bobbins were connected to a pair of -brushes touching a commutator mounted on the shaft holding the magnet, -and other brushes carried the current from the commutator so that the -alternating current generated was rectified into direct current. - -[Illustration: PIXII’S DYNAMO, 1832. - -Pixii made an improvement by rotating a permanent magnet in the -neighborhood of coils of wire mounted on a soft iron core. A commutator -rectified the alternating current generated into direct current. This -dynamo is in the collection of the Smithsonian Institution.] - -E. M. Clarke, an Englishman made, in 1834, another dynamo in which the -bobbins rotated alongside of the poles of a permanent horseshoe magnet. -He also made a commutator so that the machine produced direct current. -None of these machines gave more than feeble current at low pressure. -The large primary batteries that had been made were much more powerful, -although expensive to operate. It has been estimated that the cost of -current from the 2000-cell battery to operate the demonstration of the -arc light by Davy, was six dollars a minute. At present retail rates -for electricity sold by lighting companies, six dollars would operate -Davy’s arc light about 500 hours or 30,000 times as long. - - - - -DANIELL’S BATTERY - - -[Illustration: DANIELL’S CELL, 1836. - -Daniell invented a battery consisting of zinc, copper and copper -sulphate. Later the porous cup was dispensed with, which was used to -keep the sulphuric acid formed separate from the solution of copper -sulphate, the two liquids then being kept apart by their difference in -specific gravity. It was then called the Gravity Battery and for years -was used in telegraphy.] - -It was soon discovered that if the zinc electrode were rubbed with -mercury (amalgamated), the local action would practically cease, and if -the hydrogen bubbles were removed, the operating voltage of the cell -would be increased. John Frederic Daniell, an English chemist, invented -a cell in 1836 to overcome these difficulties. His cell consisted -of a glass jar containing a saturated solution of copper sulphate -(CuSO_{4}). A copper cylinder, open at both ends and perforated with -holes, was put into this solution. On the outside of the copper -cylinder there was a copper ring, located below the surface of the -solution, acting as a shelf to support crystals of copper sulphate. -Inside the cylinder there was a porous earthenware jar containing -dilute sulphuric acid and an amalgamated zinc rod. The two liquids were -therefore kept apart but in contact with each other through the pores -of the jar. The hydrogen gas given off by the action of the sulphuric -acid on the zinc, combined with the dissolved copper sulphate, formed -sulphuric acid and metallic copper. The latter was deposited on the -copper cylinder which acted as the other electrode. Thus the copper -sulphate acted as a depolarizer. - -The chemical reactions in this cell are, - - In inner porous jar: Zn + H_{2}SO_{4} = ZnSO_{4} + H_{2} - In outer glass jar: H_{2} + CuSO_{4} = H_{2}SO_{4} + Cu - -This cell had an open circuit voltage of a little over one volt. Later -the porous cup was dispensed with, the two liquids being kept apart -by the difference of their specific gravities. This was known as the -Gravity cell, and for years was used in telegraphy. - -[Illustration: GROVE’S CELL, 1838. - -This consisted of zinc, sulphuric acid, nitric acid and platinum. It -made a very powerful battery. The nitric acid is called the depolarizer -as it absorbs the hydrogen gas formed, thus improving the operating -voltage.] - - - - -GROVE’S BATTERY - - -Sir William Robert Grove, an English Judge and scientist, invented a -cell in 1838 consisting of a platinum electrode in strong nitric acid -in a porous earthenware jar. This jar was put in dilute sulphuric acid -in a glass jar in which there was an amalgamated zinc plate for the -other electrode. This had an open circuit voltage of about 1.9 volts. -The porous jar was used to prevent the nitric acid from attacking the -zinc. The nitric acid was used for the purpose of combining with the -hydrogen gas set free by the action of the sulphuric acid on the zinc, -and hence was the depolarizing agent. Hydrogen combining with nitric -acid forms nitrous peroxide and water. Part of the nitrous peroxide is -dissolved in the water, and the rest escapes as fumes which, however, -are very suffocating. - -The chemical equations of this cell are as follows: - - In outer glass jar: Zn + H_{2}SO_{4} = ZnSO_{4} + H_{2} - In inner porous jar: H_{2} + 2HNO_{3} = N_{2}O_{4} + 2H_{2}O - -An interesting thing about Grove’s cell is that it was planned in -accordance with a theory. Grove knew that the electrical energy of -the zinc-sulphuric acid cell came from the chemical affinity of the -two reagents, and if the hydrogen gas set free could be combined with -oxygen (to form water--H_{2}O), such chemical affinity should increase -the strength of the cell. As the hydrogen gas appears at the other -electrode, the oxidizing agent should surround that electrode. Nitric -acid was known at that time as one of the most powerful oxidizing -liquids, but as it attacks copper, he used platinum for the other -electrode. Thus he not only overcame the difficulty of polarization by -the hydrogen gas, but also increased the voltage of the cell by the -added chemical action of the combination of hydrogen and oxygen. - - - - -GROVE’S DEMONSTRATION OF INCANDESCENT LIGHTING - - -In 1840 Grove made an experimental lamp by attaching the ends of a coil -of platinum wire to copper wires, the lower parts of which were well -varnished for insulation. The platinum wire was covered by a glass -tumbler, the open end set in a glass dish partly filled with water. -This prevented draughts of air from cooling the incandescent platinum, -and the small amount of oxygen of the air in the tumbler reduced the -amount of oxidization of the platinum that would otherwise occur. With -current supplied by a large number of cells of his battery, he lighted -the auditorium of the Royal Institution with these lamps during one -of the lectures he gave. This lamp gave only a feeble light as there -was danger of melting the platinum and platinum gives but little light -unless operated close to its melting temperature. It also required a -lot of current to operate it as the air tended to cool the incandescent -platinum. The demonstration was only of scientific interest, the cost -of current being much too great (estimated at several hundred dollars a -kilowatt hour) to make it commercial. - - - - -GRENET BATTERY - - -It was discovered that chromic anhydride gives up oxygen easier than -nitric acid and consequently if used would give a higher voltage than -Grove’s nitric acid battery. It also has the advantage of a lesser -tendency to attack zinc directly if it happens to come in contact with -it. Grenet developed a cell having a liquid consisting of a mixture of -potassium bichromate (K_{2}Cr_{2}O_{7}) and sulphuric acid. A porous -cell was therefore not used to keep the two liquids apart. This had the -advantage of reducing the internal resistance. The chemical reaction -was: - - K_{2}Cr_{2}O_{7} (potassium bichromate) + 7H_{2}SO_{4} (sulphuric - acid) + 3Zn (zinc) = 3ZnSO_{4} (zinc sulphate) + K_{2}SO_{4} - (potassium sulphate) + Cr_{2} (SO_{4})_{3} (chromium sulphate) - + 7H_{2}O (water). - -In order to prevent the useless consumption of zinc on open circuit, -the zinc was attached to a sliding rod and could be drawn up into the -neck of the bottle-shaped jar containing the liquid. - -[Illustration: GROVE’S INCANDESCENT LAMP, 1840. - -Grove made an experimental lamp, using platinum for the burner which -was protected from draughts of air by a glass tumbler.] - - - - -DE MOLEYNS’ INCANDESCENT LAMP - - -Frederick De Moleyns, an Englishman, has the honor of having obtained -the first patent on an incandescent lamp. This was in 1841 and his -lamp was quite novel. It consisted of a spherical glass globe, in the -upper part of which was a tube containing powdered charcoal. This tube -was open at the bottom inside the globe and through it ran a platinum -wire, the end below the tube being coiled. Another platinum wire coiled -at its upper end came up through the lower part of the globe but did -not quite touch the other platinum coil. The powdered charcoal filled -the two coils of platinum wire and bridged the gap between. Current -passing through this charcoal bridge heated it to incandescence. The -air in the globe having been removed as far as was possible with the -hand air pumps then available, the charcoal did not immediately burn -up, the small amount consumed being replaced by the supply in the -tube. The idea was ingenious but the lamp was impractical as the globe -rapidly blackened from the evaporation of the incandescent charcoal. - -[Illustration: DE MOLEYNS’ INCANDESCENT LAMP, 1841. - -This consisted of two coils of platinum wire containing powdered -charcoal operating in a vacuum. It is only of interest as the first -incandescent lamp on which a patent (British) was granted.] - - - - -EARLY DEVELOPMENTS OF THE ARC LAMP - - -It had been found that most of the light of the arc came from the -tip of the positive electrode, and that the charcoal electrodes were -rapidly consumed, the positive electrode about twice as fast as the -negative. Mechanisms were designed to take care of this, together with -devices to start the arc by allowing the electrodes to touch each other -and then pulling them apart the proper distance. This distance varied -from one-eighth to three-quarters of an inch. - -In 1840 Bunsen, the German chemist who invented the bunsen burner, -devised a process for making hard dense carbon pencils which lasted -much longer than the charcoal previously used. The dense carbon from -the inside of the retorts of gas making plants was ground up and mixed -with molasses, moulded into shape and baked at a high temperature. -Bunsen also, in 1843, cheapened Grove’s battery by substituting a hard -carbon plate in place of the platinum electrode. - -[Illustration: WRIGHT’S ARC LAMP, 1845. - -This lamp is also only of interest as the first arc lamp on which a -patent (British) was granted. Four arcs played between the five carbon -discs.] - -Thomas Wright, an Englishman, was the first to patent an arc lamp. -This was in 1845, and the lamp was a hand regulated device consisting -of five carbon disks normally touching each other and rotated by -clockwork. Two of the disks could be drawn outward by thumb screws, -which was to be done after the current was turned on thus establishing -four arcs, one between each pair of disks. The next year, 1846, W. E. -Staite, another Englishman, made an arc lamp having two vertical carbon -pencils. The upper was stationary. The lower was movable and actuated -by clockwork directed by ratchets which in turn were regulated by an -electro-magnet controlled by the current flowing through the arc. Thus -the lower carbon would be moved up or down as required. - -Archereau, a Frenchman, made a very simple arc lamp in 1848. The upper -carbon was fixed and the lower one was mounted on a piece of iron -which could be drawn down into a coil of wire. The weight of the lower -electrode was overbalanced by a counterweight, so that when no current -was flowing the two carbons would touch. When current was turned on, it -flowed through the two carbons and through the coil of wire (solenoid) -which then became energized and pulled the lower carbon down, thus -striking the arc. Two of these arc lamps were installed in Paris -and caused considerable excitement. After a few weeks of unreliable -operation, it was found that the cost of current from the batteries was -much too great to continue their use commercially. The dynamo had not -progressed far enough to permit its use. - -[Illustration: ARCHEREAU’S ARC LAMP, 1848. - -This simple arc was controlled by an electro-magnet, and two lamps were -installed for street lighting in Paris, current being obtained from -batteries.] - - - - -JOULE’S LAW - - -Joule was an Englishman, and in 1842 began investigating the relation -between mechanical energy and heat. He first showed that, by allowing -a weight to drop from a considerable height and turn a paddle wheel in -water, the temperature of the water would increase in relation to the -work done in turning the wheel. It is now known that 778 foot-pounds -(1 lb. falling 778 feet, 10 lbs. falling 77.8 feet or 778 lbs. falling -one foot, etc.) is the mechanical equivalent of energy equal to raising -one pound of water one degree Fahrenheit. The rate of energy (power) -is the energy divided by a unit of time; thus one horsepower is 33,000 -foot-pounds per minute. Joule next investigated the relation between -heat and electric current. He made a device consisting of a vessel of -water in which there were a thermometer and an insulated coil of wire -having a considerable resistance. He found that an electric current -heated the water, and making many combinations of the amount and length -of time of current flowing and of the resistance of the wire, he -deduced the law that the energy in an electric circuit is proportional -to the square of the amount of current flowing multiplied by the length -of time and multiplied by the resistance of the wire. - -The rate of electrical energy (electric power) is therefore -proportional to the square of current multiplied by the resistance. -The electrical unit of power is now called the WATT, named in honor of -James Watt, the Englishman, who made great improvements to the steam -engine about a century ago. Thus, watts = C^{2}R and substituting the -value of R from Ohm’s law, C = E/R, we get - - Watts = Volts × Amperes - -The watt is a small unit of electric power, as can be seen from the -fact that 746 watts are equal to one horsepower. The kilowatt, kilo -being the Greek word for thousand, is 1000 watts. - -This term is an important one in the electrical industry. For example, -dynamos are rated in kilowatts, expressed as KW; the largest one -made so far is 50,000 KW which is 66,666 horsepower. Edison’s first -commercial dynamo had a capacity of 6 KW although the terms watts -and kilowatts were not in use at that time. The ordinary sizes of -incandescent lamps now used in the home are 25, 40 and 50 watts. - - - - -STARR’S INCANDESCENT LAMP - - -[Illustration: STARR’S INCANDESCENT LAMP, 1845. - -This consisted of a short carbon pencil operating in the vacuum above a -column of mercury.] - -J. W. Starr, an American, of Cincinnati, Ohio, assisted financially by -Peabody, the philanthropist, went to England where he obtained a patent -in 1845 on the lamps he had invented, although the patent was taken -out under the name of King, his attorney. One is of passing interest -only. It consisted of a strip of platinum, the active length of which -could be adjusted to fit the battery strength used, and was covered -by a glass globe to protect it from draughts of air. The other, a -carbon lamp, was the first real contribution to the art. It consisted -of a rod of carbon operating in the vacuum above a column of mercury -(Torrecellium vacuum) as in a barometer. A heavy platinum wire was -sealed in the upper closed end of a large glass tube, and connected -to the carbon rod by an iron clamp. The lower end of the carbon rod -was fastened to another iron clamp, the two clamps being held in place -and insulated from each other by a porcelain rod. Attached to the -lower clamp was a long copper wire. Just below the lower clamp, the -glass tube was narrowed down and had a length of more than 30 inches. -The tube was then filled with mercury, the bottom of the tube being -put into a vessel partly full of mercury. The mercury ran out of the -enlarged upper part of the tube, coming to rest in the narrow part -of the tube as in a barometer, so that the carbon rod was then in a -vacuum. One lamp terminal was the platinum wire extending through the -top of the tube, and the other was the mercury. Several of these lamps -were put on exhibition in London, but were not a commercial success -as they blackened very rapidly. Starr started his return trip to the -United States the next year, but died on board the ship when he was but -25 years old. - - - - -OTHER EARLY INCANDESCENT LAMPS - - -[Illustration: STAITE’S INCANDESCENT LAMP, 1848. - -The burner was of platinum and iridium.] - -[Illustration: ROBERTS’ INCANDESCENT LAMP, 1852. - -It had a graphite burner operating in vacuum.] - -In 1848 W. E. Staite, who two years previously had made an arc lamp, -invented an incandescent lamp. This consisted of a platinum-iridium -burner in the shape of an inverted U, covered by a glass globe. It had -a thumb screw for a switch, the whole device being mounted on a bracket -which was used for the return wire. E. C. Shepard, another Englishman, -obtained a patent two years later on an incandescent lamp consisting of -a weighted hollow charcoal cylinder the end of which pressed against a -charcoal cone. Current passing through this high resistance contact, -heated the charcoal to incandescence. It operated in a glass globe from -which the air could be exhausted. M. J. Roberts obtained an English -patent in 1852 on an incandescent lamp. This had a graphite rod for a -burner, which could be renewed, mounted in a glass globe. The globe was -cemented to a metallic cap fastened to a piece of pipe through which -the air could be exhausted. After being exhausted, the pipe, having a -stop cock, could be screwed on a stand to support the lamp. - -Moses G. Farmer, a professor at the Naval Training Station at Newport, -Rhode Island, lighted the parlor of his home at 11 Pearl Street, Salem, -Mass., during July, 1859, with several incandescent lamps having a -strip of platinum for the burner. The novel feature of this lamp was -that the platinum strip was narrower at the terminals than in the -center. Heat is conducted away from the terminals and by making the -burner thin at these points, the greater resistance of the ends of -the burner absorbed more electrical energy thus offsetting the heat -being conducted away. This made a more uniform degree of incandescence -throughout the length of the burner, and Prof. Farmer obtained a patent -on this principle many years later (1882). - -[Illustration: FARMER’S INCANDESCENT LAMP, 1859. - -This experimental platinum lamp was made by Professor Farmer and -several of them lighted the parlor of his home in Salem, Mass.] - - - - -FURTHER ARC LAMP DEVELOPMENTS - - -During the ten years, 1850 to 1860, several inventors developed arc -lamp mechanisms. Among them was M. J. Roberts, who had invented the -graphite incandescent lamp. In Roberts’ arc lamp, which he patented in -1852, the lower carbon was stationary. The upper carbon fitted snugly -into an iron tube. In the tube was a brass covered iron rod, which -by its weight could push the upper carbon down the tube so the two -carbons normally were in contact. An electro-magnet in series with the -arc was so located that, when energized, it pulled up the iron tube. -This magnet also held the brass covered iron rod from pushing the -upper carbon down the tube so that the two carbons were pulled apart, -striking the arc. When the arc went out, the iron tube dropped back -into its original position, the brass covered iron rod was released, -pushing the upper carbon down the tube until the two carbons again -touched. This closed the circuit again, striking the arc as before. - -[Illustration: ROBERTS’ ARC LAMP, 1852. - -The arc was controlled by an electro-magnet which held an iron tube to -which the upper carbon was fastened.] - -[Illustration: SLATER AND WATSON’S ARC LAMP, 1852. - -Clutches were used for the first time in this arc lamp to feed the -carbons.] - -In the same year (1852) Slater and Watson obtained an English patent -on an arc lamp in which the upper carbon was movable and held in place -by two clutches actuated by electro-magnets. The lower carbon was -fixed, and normally the two carbons touched each other. When current -was turned on, the electro-magnet lifted the clutches which gripped the -upper carbon, pulling it up and striking the arc. This was the first -time that a clutch was used to allow the carbon to feed as it became -consumed. - -Henry Chapman, in 1855, made an arc in which the upper carbon was -allowed to feed by gravity, but held in place by a chain wound around -a wheel. On this wheel was a brake actuated by an electro-magnet. The -lower carbon was pulled down by an electro-magnet working against a -spring. When no current was flowing or when the arc went out, the two -carbons touched. With current on, one electro-magnet set the brake and -held the upper carbon stationary. The other electro-magnet pulled the -lower carbon down, thus striking the arc. - -None of these mechanisms regulated the length of the arc. It was not -until 1856 that Joseph Lacassagne and Henry Thiers, Frenchmen, invented -the so-called “differential” method of control, which made the carbons -feed when the arc voltage, and hence length, became too great. This -principle was used in commercial arc lamps several years afterward when -they were operated on series circuits, as it had the added advantage -of preventing the feeding of one arc lamp affecting another on the -same circuit. This differential control consists in principle of two -electro-magnets, one in series with, and opposing the pull of the other -which is in shunt with the arc. The series magnet pulls the carbons -apart and strikes the arc. As the arc increases in length, its voltage -rises, thereby increasing the current flowing through the shunt magnet. -This increases the strength of the shunt magnet and, when the arc -becomes too long, the strength of the shunt becomes greater than that -of the series magnet, thus making the carbons feed. - -[Illustration: DIAGRAM OF “DIFFERENTIAL” METHOD OF CONTROL OF AN ARC -LAMP. - -This principle, invented by Lacassagne and Thiers, was used in all arc -lamps when they were commercially introduced on a large scale more than -twenty years later.] - -The actual method adopted by Lacassagne and Thiers was different from -this, but it had this principle. They used a column of mercury on -which the lower carbon floated. The upper carbon was stationary. The -height of the mercury column was regulated by a valve connected with -a reservoir of mercury. The pull of the series magnet closed the valve -fixing the height of the column. The pull of the shunt magnet tended -to open the valve, and when it overcame the pull of the series magnet -it allowed mercury to flow from the reservoir, raising the height of -the column bringing the carbons nearer together. This reduced the -arc voltage and shunt magnet strength until the valve closed again. -Thus the carbons were always kept the proper distance apart. In first -starting the arc, or if the arc should go out, current would only flow -through the shunt magnet, bringing the two carbons together until they -touched. Current would then flow through the contact of the two carbons -and through the series magnet, shutting the valve. There were no means -of pulling the carbons apart to strike the arc. Current flowing through -the high resistance of the poor contact of the two carbons, heated -their tips to incandescence. The incandescent tips would begin to burn -away, thus after a time starting an arc. The arc, however, once started -was maintained the proper length. - -[Illustration: LACASSAGNE AND THIERS’ DIFFERENTIALLY CONTROLLED ARC -LAMP, 1856. - -The lower carbon floated on a column of mercury whose height was -“differentially” controlled by series and shunt magnets.] - -In 1857, Serrin took out his first patent on an arc lamp, the general -principles of which were the same as in others he made. The mechanism -consisted of two drums, one double the diameter of the other. Both -carbons were movable, the upper one feeding down, and the lower one -feeding up, being connected with chains wound around the drums. The -difference in consumption of the two carbons was therefore compensated -for by the difference in size of the drums, thus maintaining the -location of the arc in a fixed position. A train of wheels controlled -by a pawl and regulated by an electro-magnet, controlled the movement -of the carbons. The weight of the upper carbon and its holder actuates -the train of wheels. - -[Illustration: SERRIN’S ARC LAMP, 1857. - -This type of arc was not differentially controlled but was the first -commercial lamp later used. Both carbons were movable, held by chains -wound around drums which were controlled by ratchets actuated by an -electro-magnet.] - - - - -DEVELOPMENT OF THE DYNAMO, 1840–1860 - - -During the first few years after 1840 the dynamo was only a laboratory -experiment. Woolrich devised a machine which had several pairs of -magnets and double the number of coils in order to make the current -obtained less pulsating. Wheatstone in 1845 patented the use of -electro-magnets in place of permanent magnets. Brett in 1848 suggested -that the current, generated in the coils, be allowed to flow through -a coil surrounding each permanent magnet to further strengthen the -magnets. Pulvermacher in 1849 proposed the use of thin plates of iron -for the bobbins, to reduce the eddy currents generated in the iron. -Sinsteden in 1851 suggested that the current from a permanent magnet -machine be used to excite the field coils of an electro-magnet machine. - -In 1855 Soren Hjorth, of Copenhagen, Denmark, patented a dynamo having -both permanent and electro-magnets, the latter being excited by -currents first induced in the bobbins by the permanent magnets. In 1856 -Dr. Werner Siemens invented the shuttle wound armature. This consisted -of a single coil of wire wound lengthwise and counter sunk in a long -cylindrical piece of iron. This revolved between the magnet poles which -were shaped to fit the cylindrical armature. - -[Illustration: SIEMENS’ DYNAMO, 1856. - -This dynamo was an improvement over others on account of the -construction of its “shuttle” armature.] - - - - -THE FIRST COMMERCIAL INSTALLATION OF AN ELECTRIC LIGHT - - -In 1862 a Serrin type of arc lamp was installed in the Dungeness -lighthouse in England. Current was supplied by a dynamo made by the -Alliance Company, which had been originally designed in 1850 by Nollet, -a professor of Physics in the Military School in Brussels. Nollet’s -original design was of a dynamo having several rows of permanent -magnets mounted radially on a stationary frame, with an equal number -of bobbins mounted on a shaft which rotated and had a commutator so -direct current could be obtained. A company was formed to sell hydrogen -gas for illuminating purposes, the gas to be made by the decomposition -of water with current from this machine. Nollet died and the company -failed, but it was reorganized as the Alliance Company a few years -later to exploit the arc lamp. - -[Illustration: ALLIANCE DYNAMO, 1862. - -This was the dynamo used in the first commercial installation of an arc -light in the Dungeness Lighthouse, England, 1862.] - -About the only change made in the dynamo was to substitute collector -rings for the commutator to overcome the difficulties of commutation. -Alternating current was therefore generated in this first commercial -machine. It had a capacity for but one arc light, which probably -consumed less than ten amperes at about 45 volts, hence delivered -in the present terminology not over 450 watts or about two-thirds -of a horsepower. As the bobbins of the armature undoubtedly had a -considerable resistance, the machine had an efficiency of not over 50 -per cent and therefore required at least one and a quarter horsepower -to drive it. - - - - -FURTHER DYNAMO DEVELOPMENTS - - -In the summer of 1886 Sir Charles Wheatstone constructed a self-excited -machine on the principle of using the residual magnetism in the field -poles to set up a feeble current in the armature which, passing through -the field coils, gradually strengthened the fields until they built up -to normal strength. It was later found that this idea had been thought -of by an unknown man, being disclosed by a clause in a provisional -1858 English patent taken out by his agent. Wheatstone’s machine was -shown to the Royal Society in London and a paper on it read before the -Society on February 14, 1867. The field coils were shunt wound. - -[Illustration: WHEATSTONE’S SELF-EXCITED DYNAMO, 1866. - -This machine was the first self-excited dynamo by use of the residual -magnetism in the field poles.] - -Dr. Werner Siemens also made a self-excited machine, having series -fields, a paper on which was read before the Academy of Sciences -in Berlin on January 17, 1867. This paper was forwarded to the -Royal Society in London and presented at the same meeting at which -Wheatstone’s dynamo was described. Wheatstone probably preceded Siemens -in this re-discovery of the principle of self-excitation, but both are -given the merit of it. However, S. A. Varley on December 24, 1866, -obtained a provisional English patent on this, which was not published -until July, 1867. - -[Illustration: GRAMME’S DYNAMO, 1871. - -These were commercially used, their main feature being the “ring” wound -armature.] - -[Illustration: GRAMME’S “RING” ARMATURE. - -Wire coils, surrounding an iron wire core, were all connected together -in an endless ring, each coil being tapped with a wire connected to a -commutator bar.] - -In 1870 Gramme, a Frenchman, patented his well-known ring armature. The -idea had been previously thought of by Elias, a Hollander, in 1842, and -by Pacinnotti, an Italian, as shown by the crude motors (not dynamos) -they had made. Gramme’s armature consisted of an iron wire core coated -with a bituminous compound in order to reduce the eddy currents. This -core was wound with insulated wire coils, all connected together in -series as one single endless coil. Each coil was tapped with a wire -connected to a commutator bar. His first machine, having permanent -magnets for fields, was submitted to the French Academy of Sciences in -1871. Later machines were made with self-excited field coils, which -were used in commercial service. They had, however a high resistance -armature, so that their efficiency did not exceed 50 per cent. - -[Illustration: ALTENECK’S DYNAMO WITH “DRUM” WOUND ARMATURE, 1872. - -The armature winding was entirely on the surface of the armature core, -a principle now used in all dynamos.] - -Von Hefner Alteneck, an engineer with Siemens, invented the drum wound -armature in 1872. The wires of the armature were all on the surface -of the armature core, the wires being tapped at frequent points for -connection with the commutator bars. Thus in the early seventies, -commercial dynamos were available for use in arc lighting, and a few -installations were made in Europe. - - - - -RUSSIAN INCANDESCENT LAMP INVENTORS - - -In 1872 Lodyguine, a Russian scientist, made an incandescent lamp -consisting of a “V” shaped piece of graphite for a burner, which -operated in nitrogen gas. He lighted the Admiralty Dockyard at St. -Petersburg with about two hundred of these lamps. In 1872 the Russian -Academy of Sciences awarded him a prize of 50,000 rubles (a lot of -real money at that time) for his invention. A company with a capital -of 200,000 rubles (then equal to about $100,000) was formed but as -the lamp was so expensive to operate and had such a short life, about -twelve hours, the project failed. - -[Illustration: LODYGUINE’S INCANDESCENT LAMP, 1872. - -The burner was made of graphite and operated in nitrogen gas.] - -[Illustration: KONN’S INCANDESCENT LAMP, 1875. - -In this lamp the graphite rods operated in a vacuum.] - -Kosloff, another Russian, in 1875 patented a graphite in nitrogen -incandescent lamp, which had several graphite rods for burners, so -arranged that when one failed another was automatically connected. -Konn, also a Russian, made a lamp similar to Kosloff’s except that -the graphite rods operated in a vacuum. Bouliguine, another Russian, -in 1876 made an incandescent lamp having a long graphite rod, only -the upper part of which was in circuit. As this part burned out, the -rod was automatically pushed up so that a fresh portion then was in -circuit. It operated in a vacuum. None of these lamps was commercial as -they blackened rapidly and were too expensive to maintain. - -[Illustration: BOULIGUINE’S INCANDESCENT LAMP, 1876. - -A long graphite rod, the upper part of which only was in circuit, -operated in vacuum. As this part burned out, the rod was automatically -shoved up, a fresh portion then being in the circuit.] - - - - -THE JABLOCHKOFF “CANDLE” - - -Paul Jablochkoff was a Russian army officer and an engineer. In the -early seventies he came to Paris and developed a novel arc light. This -consisted of a pair of carbons held together side by side and insulated -from each other by a mineral known as kaolin which vaporized as the -carbons were consumed. There was no mechanism, the arc being started -by a thin piece of carbon across the tips of the carbons. Current -burned this bridge, starting the arc. The early carbons were about -five inches long, and the positive carbon was twice as thick as the -negative to compensate for the unequal consumption on direct current. -This, however, did not work satisfactorily. Later the length of the -carbons was increased, the carbon made of equal thickness and burned -on alternating current of about eight or nine amperes at about 45 -volts. He made an alternating current generator which had a stationary -exterior armature with interior revolving field poles. Several -“candles,” as they were called, were put in one fixture to permit all -night service and an automatic device was developed, located in each -fixture, so that should one “candle” go out for any reason, another was -switched into service. - -[Illustration: JABLOCHKOFF “CANDLE,” 1876. - -This simple arc consisted of a pair of carbons held together side by -side and insulated from each other by kaolin. Several boulevards in -Paris were lighted with these arc lights. This arc lamp is in the -collection of the Smithsonian Institution.] - -In 1876 many of these “candles” were installed and later several of the -boulevards in Paris were lighted with them. This was the first large -installation of the arc light, and was the beginning of its commercial -introduction. Henry Wilde made some improvements in the candle by -eliminating the kaolin between the carbons which gave Jablochkoff’s arc -its peculiar color. Wilde’s arc was started by allowing the ends of the -carbons to touch each other, a magnet swinging them apart thus striking -the arc. - -[Illustration: JABLOCHKOFF’S ALTERNATING CURRENT DYNAMO, 1876. - -This dynamo had a stationary exterior armature and internal revolving -field poles. Alternating current was used for the Jablochkoff “candle” -to overcome the difficulties of unequal consumption of the carbons on -direct current.] - - -COMMERCIAL INTRODUCTION OF THE DIFFERENTIALLY CONTROLLED ARC LAMP - -About the same time Lontin, a Frenchman, improved Serrin’s arc lamp -mechanism by the application of series and shunt magnets. This is the -differential principle which was invented by Lacassagne and Thiers in -1855 but which apparently had been forgotten. Several of these lamps -were commercially installed in France beginning with 1876. - - - - -ARC LIGHTING IN THE UNITED STATES - - -[Illustration: WALLACE-FARMER ARC LAMP, 1875. - -This “differentially controlled” arc lamp consisted of two slabs of -carbon between which the arc played. In the original lamp the carbon -slabs were mounted on pieces of wood held in place by bolts, adjustment -being made by hitting the upper carbon slab with a hammer. This lamp is -in the collection of the Smithsonian Institution.] - -[Illustration: WALLACE-FARMER DYNAMO, 1875. - -This was the first commercial dynamo used in the United States for -arc lighting. This dynamo is in the collection of the Smithsonian -Institution.] - -About 1875 William Wallace of Ansonia, Connecticut, made an arc light -consisting of two rectangular carbon plates mounted on a wooden frame. -The arc played between the two edges of the plates, which lasted much -longer than rods. When the edges had burned away so that the arc then -became unduly long, the carbon plates were brought closer together by -hitting them with a hammer. Wallace became associated with Moses G. -Farmer, and they improved this crude arc by fastening the upper carbon -plate to a rod which was held by a clutch controlled by a magnet. This -magnet had two coils in one, the inner winding in series with the arc, -and outer one in shunt and opposing the series winding. The arc was -therefore differentially controlled. - -[Illustration: WESTON’S ARC LAMP, 1876. - -This lamp is in the collection of the Smithsonian Institution.] - -They also developed a series wound direct current dynamo. The armature -consisted of a number of bobbins, all connected together in an endless -ring. Each bobbin was also connected to a commutator bar. There were -two sets of bobbins, commutators and field poles, the equivalent of two -machines in one, which could be connected either to separate circuits, -or together in series on one circuit. The Wallace-Farmer system was -commercially used. The arc consumed about 20 amperes at about 35 volts, -but as the carbon plates cooled the arc, the efficiency was poor. -The arc flickered back and forth on the edges of the carbons casting -dancing shadows. The carbons, while lasting about 50 hours, were not -uniform in density, so the arc would flare up and cast off soot and -sparks. - -Edward Weston of Newark, New Jersey, also developed an arc lighting -system. His commercial lamp had carbon rods, one above the other, and -the arc was also differentially controlled. An oil dash pot prevented -undue pumping of the carbons. His dynamo had a drum-wound armature, and -had several horizontal field coils on each side of one pair of poles -between which the armature revolved. The system was designed for about -20 amperes, each are taking about 35 volts. - -[Illustration: BRUSH’S DYNAMO, 1877. - -This dynamo was used for many years for commercial arc lighting.] - -[Illustration: DIAGRAM OF BRUSH ARMATURE. - -The armature was not a closed circuit. For description of its -operation, see text.] - -Charles F. Brush made a very successful arc lighting system in 1878. -His dynamo was unique in that the armature had eight coils, one end of -each pair of opposite coils being connected together and the other ends -connected to a commutator segment. Thus the armature itself was not a -closed circuit. The machine had two pairs of horizontal poles between -which the coils revolved. One end of the one pair of coils in the most -active position was connected, by means of two of the four brushes, -in series with one end of the two pairs of coils in the lesser active -position. The latter two pairs of coils were connected in multiple -with each other by means of the brushes touching adjacent commutator -segments. The outside circuit was connected to the other two brushes, -one of which was connected to the other end of the most active pair -of coils. The other brush was connected to the other end of the two -lesser active pairs of coils. The one pair of coils in the least active -position was out of circuit. The field coils were connected in series -with the outside circuit. - -[Illustration: BRUSH’S ARC LAMP, 1877. - -The carbons were differentially controlled. This lamp was used for many -years. This lamp is in the collection of the Smithsonian Institution.] - -Brush’s arc lamp was also differentially controlled. It was designed -for about 10 amperes at about 45 volts. The carbons were copper -plated to increase their conductivity. Two pairs of carbons were used -for all-night service, each pair lasting about eight hours. A very -simple device was used to automatically switch the arc from one to -the other pair of carbons, when the first pair was consumed. This -device consisted of a triangular-shaped piece of iron connected to the -solenoid controlling the arc. There was a groove on each of the outer -two corners of this triangle, one groove wider than the other. An iron -washer surrounded each upper carbon. The edge of each washer rested -in a groove. The washer in the narrow groove made a comparatively -tight fit about its carbon. The other washer in the wider groove had -a loose fit about its carbon. Pins prevented the washer from falling -below given points. Both pairs of carbons touched each other at the -start. When current was turned on, the solenoid lifted the triangle, -the loose-fitting washer gripped its carbon first, so that current then -only passed through the other pair of carbons which were still touching -each other. The further movement of the solenoid then separated these -carbons, the arc starting between them. When this pair of carbons -became consumed, they could not feed any more so that the solenoid -would then allow the other pair of carbons to touch, transferring the -arc to that pair. - -[Illustration: THOMSON-HOUSTON ARC DYNAMO, 1878. - -This dynamo was standard for many years. This machine is in the -collection of the Smithsonian Institution.] - -Elihu Thomson and Edwin J. Houston in 1878 made a very successful and -complete arc light system. Their dynamo was specially designed to fit -the requirements of the series arc lamp. The Thomson-Houston machine -was a bipolar, having an armature consisting of three coils, one end of -each of the three coils having a common terminal, or “Y” connected, as -it is called. The other end of each coil was connected to a commutator -segment. The machine was to a great extent self-regulating, that is the -current was inherently constant with fluctuating load, as occurs when -the lamps feed or when the number of lamps burning at one time should -change for any reason. This regulation was accomplished by what is -called “armature reaction,” which is the effect the magnetization of -the armature has on the field strength. Close regulation was obtained -by a separate electro-magnet, in series with the circuit, which shifted -the brushes as the load changed. As there were but three commutator -segments, one for each coil, excessive sparking was prevented by an air -blast. - -[Illustration: DIAGRAM OF T-H ARC LIGHTING SYSTEM.] - -The “T-H” (Thompson-Houston) lamp employed the shunt feed principle. -The carbons were normally separated, being in most types drawn apart -by a spring. A high resistance magnet, shunted around the arc, served -to draw the carbons together. This occurred on starting the lamp and -thereafter the voltage of the arc was held constant by the balance -between the spring and the shunt magnet. As the carbon burned away the -mechanism advanced to a point where a clutch was tripped, the carbons -brought together, and the cycle repeated. Both the T-H and Brush -systems were extensively used in street lighting, for which they were -the standard when the open arc was superseded by the enclosed. - - - - -OTHER AMERICAN ARC LIGHT SYSTEMS - - -[Illustration: THOMSON-HOUSTON ARC LAMP, 1878. - -This is an early model with a single pair of carbons.] - -[Illustration: THOMSON DOUBLE CARBON ARC LAMP. - -This later model, having two pairs of carbons, was commercially used -for many years. This lamp is in the collection of the Smithsonian -Institution.] - -Beginning with about 1880, several arc light systems were developed. -Among these were the Vanderpoele, Hochausen, Waterhouse, Maxim, -Schuyler and Wood. The direct current carbon arc is inherently more -efficient than the alternating current lamp, owing to the fact that the -continuous flow of current in one direction maintains on the positive -carbon a larger crater at the vaporizing point of carbon. This source -furnishes the largest proportion of light, the smaller crater in the -negative carbon much less. With the alternating current arc, the large -crater is formed first on the upper and then on the lower carbon. On -account of the cooling between alternations, the mean temperature falls -below the vaporizing point of carbon, thus accounting for the lower -efficiency of the alternating current arc. - -[Illustration: MAXIM DYNAMO. - -This dynamo is in the collection of the Smithsonian Institution.] - -For this reason all these systems used direct current and the 10 ampere -ultimately displaced the 20 ampere system. The 10 ampere circuit -was later standardized at 9.6 amperes, 50 volts per lamp. The lamp -therefore consumed 480 watts giving an efficiency of about 15 lumens -per watt. This lamp gave an average of 575 candlepower (spherical) in -all directions, though it was called the 2000 cp (candlepower) arc as -under the best possible conditions it could give this candlepower in -one direction. Later a 6.6 ampere arc was developed. This was called -the “1200 cp” lamp and was not quite as efficient as the 9.6 ampere -lamp. - - - - -“SUB-DIVIDING THE ELECTRIC LIGHT” - - -While the arc lamp was being commercially established, it was at once -seen that it was too large a unit for household use. Many inventors -attacked the problem of making a smaller unit, or, as it was called, -“sub-dividing the electric light.” In the United States there were four -men prominent in this work: William E. Sawyer, Moses G. Farmer, Hiram -S. Maxim and Thomas A. Edison. These men did not make smaller arc lamps -but all attempted to make an incandescent lamp that would operate on -the arc circuits. - -[Illustration: SAWYER’S INCANDESCENT LAMP, 1878. - -This had a graphite burner operating in nitrogen gas.] - -[Illustration: FARMER’S INCANDESCENT LAMP, 1878. - -The graphite burner operated in nitrogen gas. This lamp is in the -collection of the Smithsonian Institution.] - -Sawyer made several lamps in the years 1878–79 along the lines of the -Russian scientists. All his lamps had a thick carbon burner operating -in nitrogen gas. They had a long glass tube closed at one end and the -other cemented to a brass base through which the gas was put in. Heavy -fluted wires connected the burner with the base to radiate the heat, -in order to keep the joint in the base cool. The burner was renewable -by opening the cemented joint. Farmer’s lamp consisted of a pair of -heavy copper rods mounted on a rubber cork, between which a graphite -rod was mounted. This was inserted in a glass bulb and operated in -nitrogen gas. Maxim made a lamp having a carbon burner operating in a -rarefied hydrocarbon vapor. He also made a lamp consisting of a sheet -of platinum operating in air. - - - - -EDISON’S INVENTION OF A PRACTICAL INCANDESCENT LAMP - - -Edison began the study of the problem in the spring of 1878. He had a -well-equipped laboratory at Menlo Park, New Jersey, with several able -assistants and a number of workmen, about a hundred people all told. -He had made a number of well-known inventions, among which were the -quadruplex telegraph whereby four messages could be sent simultaneously -over one wire, the carbon telephone transmitter without which Bell’s -telephone receiver would have been impracticable, and the phonograph. -All of these are in use today, so Edison was eminently fitted to attack -the problem. - -[Illustration: MAXIM’S INCANDESCENT LAMP, 1878. - -The carbon burner operated in a rarefied hydrocarbon vapor. This lamp -is in the collection of the Smithsonian Institution.] - -Edison’s first experiments were to confirm the failures of other -experimenters. Convinced of the seeming impossibility of carbon, he -turned his attention to platinum as a light giving element. Realizing -the importance of operating platinum close to its melting temperature, -he designed a lamp which had a thermostatic arrangement so that -the burner would be automatically short circuited the moment its -temperature became dangerously close to melting. The burner consisted -of a double helix of platinum wire within which was a rod. When the -temperature of the platinum became too high, the rod in expanding -would short circuit the platinum. The platinum cooled at once, the -rod contracted opening the short circuit and allowing current to flow -through the burner again. His first incandescent lamp patent covered -this lamp. His next patent covered a similar lamp with an improved -thermostat consisting of an expanding diaphragm. Both of these lamps -were designed for use on series circuits. - -[Illustration: EDISON’S FIRST EXPERIMENTAL LAMP, 1878. - -The burner was a coil of platinum wire which was protected from -operating at too high a temperature by a thermostat.] - -The only system of distributing electricity, known at that time, was -the series system. In this system current generated in the dynamo -armature flowed through the field coils, out to one lamp after another -over a wire, and then back to the dynamo. There were no means by which -one lamp could be turned on and off without doing the same with all the -others on the circuit. Edison realized that while this was satisfactory -for street lighting where arcs were generally used, it never would -be commercial for household lighting. He therefore decided that a -practical incandescent electric lighting system must be patterned -after gas lighting with which it would compete. He therefore made -an intensive study of gas distribution and reasoned that a constant -pressure electrical system could be made similar to that of gas. - -The first problem was therefore to design a dynamo that would give a -constant pressure instead of constant current. He therefore reasoned -that the internal resistance of the armature must be very low or the -voltage would fall as current was taken from the dynamo. Scientists -had shown that the most economical use of electricity from a primary -battery was where the external resistance of the load was the same as -the internal resistance of the battery, or in other words, 50 per cent -was the maximum possible efficiency. - -[Illustration: DIAGRAM OF CONSTANT CURRENT SERIES SYSTEM. - -This, in 1878, was the only method of distributing electric current.] - -[Illustration: DIAGRAM OF EDISON’S MULTIPLE SYSTEM, 1879. - -Edison invented the multiple system of distributing electric current, -now universally used.] - -When Edison proposed a very low resistance armature so that the dynamo -would have an efficiency of 90 per cent at full load, he was ridiculed. -Nevertheless he went ahead and made one which attained this. The -armature consisted of drum-wound insulated copper rods, the armature -core having circular sheets of iron with paper between to reduce the -eddy currents. There were two vertical fields above and connected in -shunt with the armature. It generated electricity at about a hundred -volts constant pressure and could supply current up to about 60 -amperes at this pressure. It therefore had a capacity, in the present -terminology, of about 6 kilowatts (or 8 horsepower). - -[Illustration: EDISON DYNAMO, 1879. - -Edison made a dynamo that was 90 per cent efficient which scientists -said was impossible. This dynamo is in the collection of the -Smithsonian Institution and was one of the machines on the steamship -Columbia, the first commercial installation of the Edison lamp.] - -A multiple system of distribution would make each lamp independent of -every other and with a dynamo made for such a system, the next thing -was to design a lamp for it. Having a pressure of about a hundred volts -to contend with, the lamp, in order to take a small amount of current, -must, to comply with Ohm’s law, have a high resistance. He therefore -wound many feet of fine platinum wire on a spool of pipe clay and -made his first high resistance lamp. He used his diaphragm thermostat -to protect the platinum from melting, and, as now seems obvious but -was not to all so-called electricians at that time, the thermostat -was arranged to open circuit instead of short circuit the burner when -it became too hot. This lamp apparently solved the problem, and, in -order to protect the platinum from the oxygen of the air, he coated -it with oxide of zirconium. Unfortunately zirconia, while an insulator -at ordinary temperatures, becomes, as is now known, a conductor of -electricity when heated, so that the lamp short circuited itself when -it was lighted. - -[Illustration: EDISON’S HIGH RESISTANCE PLATINUM LAMP, 1879. - -This lamp had a high resistance burner, necessary for the multiple -system.] - -[Illustration: EDISON’S HIGH RESISTANCE PLATINUM IN VACUUM LAMP, 1879. - -This experimental lamp led to the invention of the successful carbon -filament lamp.] - -During his experiments he had found that platinum became exceedingly -hard after it had been heated several times to incandescence by current -flowing through it. This apparently raised its melting temperature so -he was able to increase the operating temperature and therefore greatly -increase the candlepower of his lamps after they had been heated a few -times. Examination of the platinum under a microscope showed it to be -much less porous after heating, so he reasoned that gases were occluded -throughout the platinum and were driven out by the heat. This led him -to make a lamp with a platinum wire to operate in vacuum, as he thought -that more of the occluded gases would come out under such circumstances. - -[Illustration: EDISON’S CARBON LAMP OF OCTOBER 21, 1879. - -This experimental lamp, having a high resistance carbon filament -operating in a high vacuum maintained by an all-glass globe, was the -keystone of Edison’s successful incandescent lighting system. All -incandescent lamps made today embody the basic features of this lamp. -This replica is in the Smithsonian Institution exhibit of Edison lamps. -The original was destroyed.] - -These lamps were expensive to make, and, knowing that he could get the -requisite high resistance at much less cost from a long and slender -piece of carbon, he thought he might be able to make the carbon last -in the high vacuum he had been able to obtain from the newly invented -Geissler and Sprengel mercury air pumps. After several trials he -finally was able to carbonize a piece of ordinary sewing thread. This -he mounted in a one-piece all glass globe, all joints fused by melting -the glass together, which he considered was essential in order to -maintain the high vacuum. Platinum wires were fused in the glass to -connect the carbonized thread inside the bulb with the circuit outside -as platinum has the same coefficient of expansion as glass and hence -maintains an airtight joint. He reasoned that there would be occluded -gases in the carbonized thread which would immediately burn up if the -slightest trace of oxygen were present, so he heated the lamp while it -was still on the exhaust pump after a high degree of vacuum had been -obtained. This was accomplished by passing a small amount of current -through the “filament,” as he called it, gently heating it. Immediately -the gases started coming out, and it took eight hours more on the pump -before they stopped. The lamp was then sealed and ready for trial. - -[Illustration: DEMONSTRATION OF EDISON’S INCANDESCENT LIGHTING SYSTEM. - -Showing view of Menlo Park Laboratory Buildings, 1880.] - -On October 21, 1879, current was turned into the lamp and it lasted -forty-five hours before it failed. A patent was applied for on November -4th of that year and granted January 27, 1880. All incandescent lamps -made today embody the basic features of this lamp. Edison immediately -began a searching investigation of the best material for a filament and -soon found that carbonized paper gave several hundred hours life. This -made it commercially possible, so in December, 1879, it was decided -that a public demonstration of his incandescent lighting system should -be made. Wires were run to several houses in Menlo Park, N. J., and -lamps were also mounted on poles, lighting the country roads in the -neighborhood. An article appeared in the New York Herald on Sunday, -December 21, 1879, describing Edison’s invention and telling of the -public demonstration to be given during the Christmas holidays. This -occupied the entire first page of the paper, and created such a furor -that the Pennsylvania Railroad had to run special trains to Menlo -Park to accommodate the crowds. The first commercially successful -installation of the Edison incandescent lamps and lighting system was -made on the steamship Columbia, which started May 2, 1880, on a voyage -around Cape Horn to San Francisco, Calif. - -The carbonized paper filament of the first commercial incandescent lamp -was quite fragile. Early in 1880 carbonized bamboo was found to be not -only sturdy but made an even better filament than paper. The shape of -the bulb was also changed from round to pear shape, being blown from -one inch tubing. Later the bulbs were blown directly from molten glass. - -[Illustration: DYNAMO ROOM, S. S. COLUMBIA. - -The first commercial installation of the Edison Lamp, started May 2, -1880. One of these original dynamos is on exhibit at the Smithsonian -Institution.] - -As it was inconvenient to connect the wires to the binding posts of -a new lamp every time a burned out lamp had to be replaced, a base -and socket for it were developed. The earliest form of base consisted -simply of bending the two wires of the lamp back on the neck of the -bulb and holding them in place by wrapping string around the neck. The -socket consisted of two pieces of sheet copper in a hollow piece of -wood. The lamp was inserted in this, the two-wire terminals of the lamp -making contact with the two-sheet copper terminals of the socket, the -lamp being rigidly held in the socket by a thumb screw which forced -the socket terminals tight against the neck of the bulb. - -[Illustration: ORIGINAL SOCKET FOR INCANDESCENT LAMPS, 1880.] - -[Illustration: WIRE TERMINAL BASE LAMP, 1880. - -This crude form of lamp base fitted the original form of lamp socket -pictured above. This lamp is in the exhibit of Edison lamps in the -Smithsonian Institution.] - -This crude arrangement was changed in the latter part of 1880 to a -screw shell and a ring for the base terminals, wood being used for -insulation. The socket was correspondingly changed. This was a very -bulky affair, so the base was changed to a cone-shaped ring and a -screw shell for terminals. Wood was used for insulation, which a short -time after was changed to plaster of Paris as this was also used to -fasten the base to the bulb. It was soon found that the tension created -between the two terminals of the base when the lamp was firmly screwed -in the socket often caused the plaster base to pull apart, so the shape -of the base was again changed early in 1881, to the form in use today. - -An improved method of connecting the ends of the filament to the -leading-in wires was adopted early in 1881. Formerly this was -accomplished by a delicate clamp having a bolt and nut. The improvement -consisted of copper plating the filament to the leading-in wire. - -[Illustration: ORIGINAL SCREW BASE LAMP, 1880. - -This first screw base, consisting of a screw shell and ring for -terminals with wood for insulation, was a very bulky affair. This lamp -is in the exhibit of Edison lamps in the Smithsonian Institution.] - -[Illustration: IMPROVED SCREW BASE LAMP, 1881. - -The terminals of this base consisted of a cone shaped ring and a screw -shell. At first wood was used for insulation, later plaster of paris -which was also used to fasten the base to the bulb. This lamp is in the -exhibit of Edison lamps in the Smithsonian Institution.] - -In the early part of the year 1881 the lamps were made “eight to -the horsepower.” Each lamp, therefore, consumed a little less than -100 watts, and was designed to give 16 candlepower in a horizontal -direction. The average candlepower (spherical) in all directions was -about 77 per cent of this, hence as the modern term “lumen” is 12.57 -spherical candlepower, these lamps had an initial efficiency of about -1.7 lumens per watt. The lamps blackened considerably during their life -so that just before they burned out their candlepower was less than -half that when new. Thus their mean efficiency throughout life was -about 1.1 l-p-w (lumens per watt). These figures are interesting in -comparison with the modern 100-watt gas-filled tungsten-filament lamp -which has an initial efficiency of 12.9, and a mean efficiency of 11.8, -l-p-w. In other words the equivalent (wattage) size of modern lamp -gives over seven times when new, and eleven times on the average, as -much light for the same energy consumption as Edison’s first commercial -lamp. In the latter part of 1881 the efficiency was changed to “ten -lamps per horsepower,” equivalent to 2¼ l-p-w initially. Two sizes of -lamps were made: 16 cp for use on 110-volt circuits and 8 cp for use -either direct on 55 volts or two in series on 110-volt circuits. - -[Illustration: FINAL FORM OF SCREW BASE, 1881. - -With plaster of paris, the previous form of base was apt to pull apart -when the lamp was firmly screwed into the socket. The form of the base -was therefore changed to that shown, which overcame these difficulties, -and which has been used ever since. The lamp shown was standard for -three years and is in the exhibit of Edison lamps in the Smithsonian -Institution.] - - - - -EDISON’S THREE-WIRE SYSTEM - - -The distance at which current can be economically delivered at 110 -volts pressure is limited, as will be seen from a study of Ohm’s law. -The loss of power in the distributing wires is proportional to the -square of the current flowing. If the voltage be doubled, the amount -of current is halved, for a given amount of electric power delivered, -so that the size of the distributing wires can then be reduced to -one-quarter for a given loss in them. At that time (1881) it was -impossible to make 220-volt lamps, and though they are now available, -their use is uneconomical, as their efficiency is much poorer than that -of 110-volt incandescent lamps. - -Edison invented a distributing system that had two 110-volt circuits, -with one wire called the neutral, common to both circuits so that the -pressure on the two outside wires was 220 volts. The neutral wire had -only to be large enough to carry the difference between the currents -flowing in the two circuits. As the load could be so arranged that it -would be approximately equal at all times on both circuits, the neutral -wire could be relatively small in size. Thus the three-wire system -resulted in a saving of 60 per cent in copper over the two-wire system -or, for the same amount of copper, the distance that current could be -delivered was more than doubled. - -[Illustration: DIAGRAM OF EDISON’S THREE-WIRE SYSTEM, 1881. - -This system reduced the cost of copper in the multiple distributing -system 60 per cent.] - - -DEVELOPMENT OF THE ALTERNATING CURRENT CONSTANT POTENTIAL SYSTEM - -The distance that current can be economically distributed, as has -been shown, depends upon the voltage used. If, therefore, current -could be sent out at a high voltage and the pressure brought down to -that desired at the various points to which it is distributed, such -distribution could cover a much greater area. Lucien Gaulard was a -French inventor and was backed by an Englishman named John D. Gibbs. -About 1882 they patented a series alternating-current system of -distribution. They had invented what is now called a transformer which -consisted of two separate coils of wire mounted on an iron core. All -the primary coils were connected in series, which, when current went -through them, induced a current in the secondary coils. Lamps were -connected in multiple on each of the secondary coils. An American -patent was applied for on the transformer, but was refused on the basis -that “more current cannot be taken from it than is put in.” While -this is true if the word energy were used, the transformer can supply -a greater current at a lower voltage (or vice versa) than is put in, -the ratio being in proportion to the relative number of turns in the -primary and secondary coils. The transformer was treated with ridicule -and Gaulard died under distressing circumstances. - -[Illustration: DIAGRAM OF STANLEY’S ALTERNATING CURRENT MULTIPLE -SYSTEM, 1885. - -This system is now universally used for distributing electric current -long distances.] - -Information regarding the transformer came to the attention of -William Stanley, an American, in the latter part of 1885. He made an -intensive study of the scheme, and developed a transformer in which -the primary coil was connected in multiple on a constant potential -alternating-current high-voltage system. From the secondary coil a -lower constant voltage was obtained. An experimental installation -was made at Great Barrington, Mass., in the early part of 1886, the -first commercial installation being made in Buffalo, New York, in the -latter part of the year. This scheme enabled current to be economically -distributed to much greater distances. The voltage of the high-tension -circuit has been gradually increased as the art has progressed from -about a thousand volts to over two hundred thousand volts pressure in a -recent installation in California, where electric power is transmitted -over two hundred miles. - - - - -INCANDESCENT LAMP DEVELOPMENTS, 1884–1894 - - -In 1884 the ring of plaster around the top of the base was omitted; in -1886 an improvement was made by pasting the filament to the leading-in -wires with a carbon paste instead of the electro-plating method; and -in 1888 the length of the base was increased so that it had more -threads. Several concerns started making incandescent lamps, the -filaments being made by carbonizing various substances. “Parchmentized” -thread consisted of ordinary thread passed through sulphuric acid. -“Tamadine” was cellulose in the sheet form, punched out in the shape -of the filament. Squirted cellulose in the form of a thread was also -used. This was made by dissolving absorbent cotton in zinc chloride, -the resulting syrup being squirted through a die into alcohol which -hardened the thread thus formed. This thread was washed in water, dried -in the air and then cut to proper length and carbonized. - -[Illustration: STANDARD EDISON LAMP, 1884. - -The ring of plaster around the neck of previous lamps was omitted. This -lamp is in the exhibit of Edison lamps in the Smithsonian Institution.] - -[Illustration: STANDARD EDISON LAMP, 1888. - -The length of the base was increased so it had more threads. This lamp -is in the exhibit of Edison lamps in the Smithsonian Institution.] - -The filament was improved by coating it with graphite. One method, -adopted about 1888, was to dip it in a hydrocarbon liquid before -carbonizing. Another, more generally adopted in 1893 was a process -originally invented by Sawyer, one of the Americans who had attempted -to “sub-divide the electric light” in 1878–79. This process consisted -of passing current through a carbonized filament in an atmosphere of -hydrocarbon vapor. The hot filament decomposed the vapor, depositing -graphite on the filament. The graphite coated filament improved it so -it could operate at 3½ lumens per watt (initial efficiency). Lamps of -20, 24, 32 and 50 candlepower were developed for 110-volt circuits. -Lamps in various sizes from 12 to 36 cp were made for use on storage -batteries having various numbers of cells and giving a voltage of -from 20 to 40 volts. Miniature lamps of from ½ to 2 cp for use on dry -batteries of from 2½ to 5½ volts, and 3 to 6 cp on 5½ to 12 volts, were -also made. These could also be connected in series on 110 volts for -festoons. Very small lamps of ½ cp of 2 to 4 volts for use in dentistry -and surgery were made available. These miniature lamps had no bases, -wires being used to connect them to the circuit. - -[Illustration: STANDARD EDISON LAMP, 1894. - -This lamp had a “treated” cellulose filament, permitting an efficiency -of 3½ lumens per watt which has never been exceeded in a carbon -lamp. This lamp is in the exhibit of Edison lamps in the Smithsonian -Institution.] - -Lamps for 220-volt circuits were developed as this voltage was -desirable for power purposes, electric motors being used, and a few -lamps were needed on such circuits. They are less efficient and more -expensive than 110-volt lamps, their use being justified however -only when it is uneconomical to have a separate 110-volt circuit for -lighting. The lamps were made in sizes from 16 to 50 candlepower. - -[Illustration: - - Edison. Thomson-Houston. Westinghouse. Brush-Swan. - - Edi-Swan Edi-Swan United States. Hawkeye. - (single contact). (double contact). - - Ft. Wayne Jenny. Mather or Perkins. Loomis. - - Schaeffer or National. Indianapolis Jenny. Siemens & Halske. - -VARIOUS STANDARD BASES IN USE, 1892.] - -[Illustration: THOMSON-HOUSTON SOCKET.] - -[Illustration: WESTINGHOUSE SOCKET.] - -Electric street railway systems used a voltage in the neighborhood of -550, and lamps were designed to burn five in series on this voltage. -These lamps were different from the standard 110-volt lamps although -they were made for about this voltage. As they were burned in series, -the lamps were selected to operate at a definite current instead of -at a definite voltage, so that the lamps when burned in series would -operate at the proper temperature to give proper life results. Such -lamps would therefore vary considerably in individual volts, and -hence would not give good service if burned on 110-volt circuits. The -candelabra screw base and socket and the miniature screw base and -socket were later developed. Ornamental candelabra base lamps were made -for use direct on 110 volts, smaller sizes being operated in series -on this voltage. The former gave about 10 cp, the latter in various -sizes from 4 to 8 cp. The miniature screw base lamps were for low volt -lighting. - -[Illustration: - - Thomson-Houston. Westinghouse. - -ADAPTERS FOR EDISON SCREW SOCKETS, 1892. - -Next to the Edison base, the Thomson-Houston and Westinghouse bases -were the most popular. By use of these adapters, Edison base lamps -could be used in T-H and Westinghouse sockets.] - -The various manufacturers of lamps in nearly every instance made bases -that were very different from one another. No less than fourteen -different standard bases and sockets came into commercial use. -These were known as, Brush-Swan, Edison, Edi-Swan (double contact), -Edi-Swan (single contact), Fort Wayne Jenny, Hawkeye, Indianapolis -Jenny, Loomis, Mather or Perkins, Schaeffer or National, Siemens & -Halske, Thomson-Houston, United States and Westinghouse. In addition -there were later larger sized bases made for use on series circuits. -These were called the Bernstein, Heisler, Large Edison, Municipal -Bernstein, Municipal Edison, Thomson-Houston (alternating circuit) and -Thomson-Houston (arc circuit). Some of these bases disappeared from -use and in 1900 the proportion in the United States was about 70 per -cent Edison, 15 per cent Westinghouse, 10 per cent Thomson-Houston -and 5 per cent for all the others remaining. A campaign was started -to standardize the Edison base, adapters being sold at cost for the -Westinghouse and Thomson-Houston sockets so that Edison base lamps -could be used. In a few years the desired results were obtained so that -now there are no other sockets in the United States but the Edison -screw type for standard lighting service. This applies also to all -other countries in the world except England where the bayonet form of -base and socket is still popular. - -[Illustration: - - Bernstein. Heisler. Thomson-Houston - (alternating current). - - Thomson-Houston Municipal Edison. Municipal Bernstein. - (arc circuit). - -VARIOUS SERIES BASES IN USE, 1892. - -The above six bases have been superseded by the “Large Edison,” now -called the Mogul Screw base.] - - - - -THE EDISON “MUNICIPAL” STREET LIGHTING SYSTEM - - - - -[Illustration: EDISON “MUNICIPAL” SYSTEM, 1885. - - -High voltage direct current was generated, several circuits operating -in multiple, three ampere lamps burning in series on each circuit. -Photograph courtesy of Association of Edison Illuminating Companies.] - -The arc lamp could not practically be made in a unit smaller than -the so-called “1200 candlepower” (6.6 ampere) or “half” size, which -really gave about 350 spherical candlepower. A demand therefore arose -for a small street lighting unit, and Edison designed his “Municipal” -street lighting system to fill this requirement. His experience in the -making of dynamos enabled him to make a direct current bipolar constant -potential machine that would deliver 1000 volts which later was -increased to 1200 volts. They were first made in two sizes having an -output of 12 and 30 amperes respectively. Incandescent lamps were made -for 3 amperes in several sizes from 16 to 50 candlepower. These lamps -were burned in series on the 1200-volt direct current system. Thus the -12-ampere machine had a capacity for four series circuits, each taking -3 amperes, the series circuits being connected in multiple across the -1200 volts. The number of lamps on each series circuit depended upon -their size, as the voltage of each lamp was different for each size, -being about 1½ volts per cp. - -A popular size was the 32-candlepower unit, which therefore required -about 45 volts and hence at 3 amperes consumed about 135 watts. -Allowing 5 per cent loss in the wires of each circuit, there was -therefore 1140 of the 1200 volts left for the lamps. Hence about 25 -32-candlepower or 50 16-candlepower lamps could be put on each series -circuit. Different sizes of lamps could also be put on the same -circuit, the number depending upon the aggregate voltage of the lamps. - -[Illustration: EDISON MUNICIPAL LAMP, 1885. - -Inside the base was an arrangement by which the lamp was automatically -short circuited when it burned out.] - -A device was put in the base of each lamp to short circuit the lamp -when it burned out so as to prevent all the other lamps on that circuit -from going out. This device consisted of a piece of wire put inside -the lamp bulb between the two ends of the filament. Connected to this -wire was a very thin wire inside the base which held a piece of metal -compressed against a spring. The spring was connected to one terminal -of the base. Should the lamp burn out, current would jump from the -filament to the wire in the bulb, and the current then flowed through -the thin wire to the other terminal of the base. The thin wire was -melted by the current, and the spring pushed the piece of metal up -short circuiting the terminals of the base. This scheme was later -simplified by omitting the wire, spring, etc., and substituting a piece -of metal which was prevented from short circuiting the terminals of -the base by a thin piece of paper. When the lamp burned out the entire -1200 volts was impressed across this piece of paper, puncturing it and -so short circuiting the base terminals. Should one or more lamps go -out on a circuit, the increase in current above the normal 3 amperes -was prevented by an adjustable resistance, or an extra lot of lamps -which could be turned on one at a time, connected to each circuit and -located in the power station under the control of the operator. This -system disappeared from use with the advent of the constant current -transformer. - - - - -THE SHUNT BOX SYSTEM FOR SERIES INCANDESCENT LAMPS - - -[Illustration: SHUNT BOX SYSTEM, 1887. - -Lamps were burned in series on a high voltage alternating current, and -when a lamp burned out all the current then went through its “shunt -box,” a reactance coil in multiple with each lamp.] - -Soon after the commercial development of the alternating current -constant potential system, a scheme was developed to permit the use -of lamps in series on such circuits without the necessity for short -circuiting a lamp should it burn out. A reactance, called a “shunt box” -and consisting of a coil of wire wound on an iron core, was connected -across each lamp. The shunt box consumed but little current while the -lamp was burning. Should one lamp go out, the entire current would -flow through its shunt box and so maintain the current approximately -constant. It had the difficulty, however, that if several lamps went -out, the current would be materially increased tending to burn out the -remaining lamps on the circuit. This system also disappeared from use -with the development of the constant current transformer. - - - - -THE ENCLOSED ARC LAMP - - -Up to 1893 the carbons of an arc lamp operated in the open air, so -that they were rapidly consumed, lasting from eight to sixteen hours -depending on their length and thickness. Louis B. Marks, an American, -found that by placing a tight fitting globe about the arc, the life -of the carbons was increased ten to twelve times. This was due to the -restricted amount of oxygen of the air in the presence of the hot -carbon tips and thus retarded their consumption. The amount of light -was somewhat decreased, but this was more than offset by the lesser -expense of trimming which also justified the use of more expensive -better quality carbons. Satisfactory operation required that the arc -voltage be increased to about 80 volts. - -[Illustration: ENCLOSED ARC LAMP, 1893. - -Enclosing the arc lengthened the life of the carbons, thereby greatly -reducing the cost of maintenance.] - -This lamp rapidly displaced the series open arc. An enclosed arc lamp -for use on 110-volt constant potential circuits was also developed. A -resistance was put in series with the arc for use on 110-volt direct -current circuits, to act as a ballast in order to prevent the arc from -taking too much current and also to use up the difference between the -arc voltage (80) and the line voltage (110). On alternating current, a -reactance was used in place of the resistance. - -The efficiencies in lumens per watt of these arcs (with clear -glassware), all of which have now disappeared from the market, were -about as follows: - - 6.6 ampere 510 watt direct current (D.C.) series arc, 8¼ l-p-w. - 5.0 ampere 550 watt direct current multiple (110-volt) arc, 4½ l-p-w. - 7.5 ampere 540 watt alternating current (A.C.) multiple (110-volt) - arc, 4¼ l-p-w. - -[Illustration: OPEN FLAME ARC LAMP, 1898. - -Certain salts impregnated in the carbons produced a brilliantly -luminous flame in the arc stream which enormously increased the -efficiency of the lamp.] - -[Illustration: ENCLOSED FLAME ARC LAMP, 1908. - -By condensing the smoke from the arc in a cooling chamber it was -practical to enclose the flame arc, thereby increasing the life of the -carbons.] - -The reason for the big difference in efficiency between the series -and multiple direct-current arc is that in the latter a large amount -of electrical energy (watts) is lost in the ballast resistance. While -there is a considerable difference between the inherent efficiencies -of the D. C. and A. C. arcs themselves, this difference is reduced in -the multiple D. C. and A. C. arc lamps as more watts are lost in the -resistance ballast of the multiple D. C. lamp than are lost in the -reactance ballast of the multiple A. C. lamp. - -This reactance gives the A. C. lamp what is called a “power-factor.” -The product of the amperes (7.5) times the volts (110) does not give -the true wattage (540) of the lamp, so that the actual volt-amperes -(825) has to be multiplied by a power factor, in this case about 65 -per cent, to obtain the actual power (watts) consumed. The reason -is that the instantaneous varying values of the alternating current -and pressure, if multiplied and averaged throughout the complete -alternating cycle, do not equal the average amperes (measured by an -ammeter) multiplied by the average voltage (measured by a volt-meter). -That is, the maximum value of the current flowing (amperes) does not -occur at the same instant that the maximum pressure (voltage) is on the -circuit. - - - - -THE FLAME ARC LAMP - - -About 1844 Bunsen investigated the effect of introducing various -chemicals in the carbon arc. Nothing was done, however, until Bremer, -a German, experimented with various salts impregnated in the carbon -electrodes. In 1898 he produced the so-called flame arc, which -consisted of carbons impregnated with calcium fluoride. This gave a -brilliant yellow light most of which came from the arc flame, and -practically none from the carbon tips. The arc operated in the open air -and produced smoke which condensed into a white powder. - -The two carbons were inclined downward at about a 30-degree angle with -each other, and were of small diameter but long, 18 to 30 inches, -having a life of about 12 to 15 hours. The tips of the carbons -projected through an inverted earthenware cup, called the “economizer,” -the white powder condensing on this and acting not only as an excellent -reflector but making a dead air space above the arc. The arc was -maintained at the tips of the carbons by an electro-magnet whose -magnetic field “blew” the arc down. - -Two flame arc lamps were burned in series on 110-volt circuits. They -consumed 550 watts each, giving an efficiency of about 35 lumens per -watt on direct current. On alternating current the efficiency was about -30 l-p-w. By use of barium salts impregnated in the carbons, a white -light was obtained, giving an efficiency of about 18 l-p-w on direct -current and about 15½ on alternating current. These figures cover lamps -equipped with clear glassware. Using strontium salts in the carbons, -a red light was obtained at a considerably lower efficiency, such -arcs on account of their color being used only to a limited extent for -advertising purposes. - -[Illustration: CONSTANT CURRENT TRANSFORMER, 1900. - -This converted alternating current of constant voltage into constant -current, for use on series circuits.] - -These arcs were remarkably efficient but their maintenance expense was -high. Later, about 1908, enclosed flame arcs with vertical carbons were -made which increased the life of the carbons, the smoke being condensed -in cooling chambers. However, their maintenance expense was still high. -They have now disappeared from the market, having been displaced by the -very efficient gas-filled tungsten filament incandescent lamp which -appeared in 1913. - - - - -THE CONSTANT CURRENT TRANSFORMER FOR SERIES CIRCUITS - - -About 1900 the constant current transformer was developed by Elihu -Thomson. This transforms current taken from a constant potential -alternating current circuit into a constant alternating current for -series circuits, whose voltage varies with the load on the circuit. -The transformer has two separate coils; the primary being stationary -and connected to the constant potential circuit and the secondary -being movable and connected to the series circuit. The weight of the -secondary coil is slightly underbalanced by a counter weight. Current -flowing in the primary induces current in the secondary, the two coils -repelling each other. The strength of the repelling force depends -upon the amount of current flowing in the two coils. The core of the -transformer is so designed that the central part, which the two coils -surround, is magnetically more powerful close to the primary coil than -it is further away. - -When the two coils are close together a higher voltage is induced in -the secondary than if the later were further away from the primary -coil. In starting, the two coils are pulled apart by hand to prevent -too large a current flowing in the series circuit. The secondary -coil is allowed to gradually fall and will come to rest at a point -where the voltage induced in it produces the normal current in the -series circuit, the repelling force between the two coils holding the -secondary at this point. Should the load in the series circuit change -for any reason, the current in the series circuit would also change, -thus changing the force repelling the two coils. The secondary would -therefore move until the current in the series circuit again becomes -normal. The action is therefore automatic, and the actual current -in the series circuit can be adjusted within limits to the desired -amount, by varying the counterweight. A dash pot is used to prevent the -secondary coil from oscillating (pumping) too much. - -In the constant current transformer, the series circuit is insulated -from the constant potential circuit. This has many advantages. A -similar device, called an automatic regulating reactance was developed -which is slightly less expensive, but it does not have the advantage of -insulating the two circuits from each other. - - - - -ENCLOSED SERIES ALTERNATING CURRENT ARC LAMPS - - -The simplicity of the constant current transformer soon drove the -constant direct-current dynamo from the market. An enclosed arc lamp -was therefore developed for use on alternating constant current. Two -sizes of lamps were made; one for 6.6 amperes consuming 450 watts -and having an efficiency of about 4½ lumens per watt, and the other -7.5 amperes, 480 watts and 5 l-p-w (clear glassware). These lamps -soon superseded the direct current series arcs. They have now been -superseded by the more efficient magnetite arc and tungsten filament -incandescent lamps. - - - - -SERIES INCANDESCENT LAMPS ON CONSTANT CURRENT TRANSFORMERS - - -Series incandescent lamps were made for use on constant current -transformers superseding the “Municipal” and “Shunt Box” systems. The -large Edison, now called the Mogul Screw base, was adopted and the -short circuiting film cut-out was removed from the base and placed -between prongs attached to the socket. - -[Illustration: - - Holder. Socket. Holder and socket. - -SERIES INCANDESCENT LAMP SOCKET WITH FILM CUTOUT, 1900. - -The “Large Edison,” now called Mogul Screw, base was standardized and -the short circuiting device put on the socket terminals.] - -The transformers made for the two sizes of arc lamps, produced 6.6 -and 7.5 amperes and incandescent lamps, in various sizes from 16 to -50 cp, were made for these currents so that the incandescent lamps -could be operated on the same circuit with the arc lamps. The carbon -series incandescent lamp, however, was more efficient if made for lower -currents, so 3½-, 4- and 5½-ampere constant current transformers were -made for incandescent lamps designed for these amperes. Later, however, -with the advent of the tungsten filament, the 6.6-ampere series -tungsten lamp was made the standard, as it was slightly more efficient -than the lower current lamps, and was made in sizes from 32 to 400 cp. -When the more efficient gas-filled tungsten lamps were developed, the -sizes were further increased; the standard 6.6-ampere lamps now made -are from 60 to 2500 cp. - - - - -THE NERNST LAMP - - -Dr. Walther Nernst, of Germany, investigating the rare earths used in -the Welsbach mantle, developed an electric lamp having a burner, or -“glower” as it was called, consisting of a mixture of these oxides. The -main ingredient was zirconia, and the glower operated in the open air. -It is a non-conductor when cold, so had to be heated before current -would flow through it. This was accomplished by an electric heating -coil, made of platinum wire, located just above the glower. As the -glower became heated and current flowed through it, the heater was -automatically disconnected by an electro-magnet cut-out. - -[Illustration: NERNST LAMP, 1900. - -The burners consisted mainly of zirconium oxide which had to be heated -before current could go through them.] - -The resistance of the glower decreases with increase in current, so a -steadying resistance was put in series with it. This consisted of an -iron wire mounted in a bulb filled with hydrogen gas and was called -a “ballast.” Iron has the property of increasing in resistance with -increase in current flowing through it, this increase being very -marked between certain temperatures at which the ballast was operated. -The lamp was put on the American market in 1900 for use on 220-volt -alternating current circuits. The glower consumed 0.4 ampere. One, two, -three, four and six glower lamps were made, consuming 88, 196, 274, 392 -and 528 watts respectively. As most of the light is thrown downward, -their light output was generally given in mean lower hemispherical -candlepower. The multiple glower lamps were more efficient than the -single glower, owing to the heat radiated from one glower to another. -Their efficiencies, depending on the size, were from about 3½ to 5 -lumens per watt, and their average candlepower throughout life was -about 80 per cent of initial. The lamp disappeared from the market -about 1912. - -[Illustration: DIAGRAM OF NERNST LAMP.] - - - - -THE COOPER-HEWITT LAMP - - -In 1860 Way discovered that if an electric circuit was opened between -mercury contacts a brilliant greenish colored arc was produced. -Mercury was an expensive metal and as the carbon arc seemed to give -the most desirable results, nothing further was done for many years -until Dr. Peter Cooper Hewitt, an American, began experimenting with -it. He finally produced an arc in vacuum in a one-inch glass tube -about 50 inches long for 110 volts direct current circuits, which was -commercialized in 1901. The tube hangs at about 15 degrees from the -horizontal. The lower end contains a small quantity of mercury. The -terminals are at each end of the tube, and the arc was first started -by tilting the tube by hand so that a thin stream of mercury bridged -the two terminals. Current immediately vaporized the mercury, starting -the arc. A resistance is put in series with the arc to maintain the -current constant on direct current constant voltage circuits. Automatic -starting devices were later developed, one of which consisted of an -electro-magnet that tilted the lamp, and the other of an induction coil -giving a high voltage which, in discharging, started the arc. - -[Illustration: COOPER-HEWITT MERCURY VAPOR ARC LAMP, 1901. - -This gives a very efficient light, practically devoid of red but of -high actinic value, so useful in photography.] - -This lamp is particularly useful in photography on account of the -high actinic value of its light. Its light is very diffused and is -practically devoid of red rays, so that red objects appear black in its -light. The lamp consumes 3½ amperes at 110 volts direct current (385 -watts) having an efficiency of about 12½ lumens per watt. - -The mercury arc is peculiar in that it acts as an electric valve -tending to let current flow through it only in one direction. Thus -on alternating current, the current impulses will readily go through -it in one direction, but the arc will go out in the other half cycle -unless means are taken to prevent this. This is accomplished by having -two terminals at one end of the tube, which are connected to choke -coils, which in turn are connected to a single coil (auto) transformer. -The alternating current supply mains are connected to wires tapping -different parts of the coil of the auto transformer. The center of -the coil of the auto transformer is connected through an induction -coil to the other end of the tube. By this means the alternating -current impulses are sent through the tube in one direction, one half -cycle from one of the pairs of terminals of the tube, the other half -cycle from the other terminal. Thus pulsating direct current, kept -constant by the induction coil, flows through the tube, the pulsations -overlapping each other by the magnetic action of the choke coils. This -alternating current lamp is started by the high voltage discharge -method. It has a 50-inch length of tube, consuming about 400 watts on -110 volts. Its efficiency is a little less than that of the direct -current lamp. - -[Illustration: DIAGRAM OF COOPER-HEWITT LAMP FOR USE ON ALTERNATING -CURRENT. - -The mercury arc is inherently for use on direct current, but by means -of reactance coils, it can be operated on alternating current.] - - - - -THE LUMINOUS OR MAGNETITE ARC LAMP - - -About 1901 Dr. Charles P. Steinmetz, Schenectady, N. Y., studied the -effect of metallic salts in the arc flame. Dr. Willis R. Whitney, -also of Schenectady, and director of the research laboratory of the -organization of which Dr. Steinmetz is the consulting engineer, -followed with some further work along this line. The results of this -work were incorporated in a commercial lamp called the magnetite arc -lamp, through the efforts of C. A. B. Halvorson, Jr., at Lynn, Mass. -The negative electrode consists of a pulverized mixture of magnetite -(a variety of iron ore) and other substances packed tightly in an iron -tube. The positive electrode is a piece of copper sheathed in iron to -prevent oxidization of the copper. The arc flame gives a brilliant -white light, and, similar to the mercury arc, is inherently limited to -direct current. It burns in the open air at about 75 volts. The lamp is -made for 4-ampere direct current series circuits and consumes about 310 -watts and has an efficiency of about 11½ lumens per watt. - -[Illustration: LUMINOUS OR MAGNETITE ARC LAMP, 1902. - -This has a negative electrode containing magnetite which produces a -very luminous white flame in the arc stream.] - -The negative (iron tube) electrode now has a life of about 350 hours. -Later, a higher efficiency, 4-ampere electrode was made which has -a shorter life but gives an efficiency of about 17 l-p-w, and a -6.6-ampere lamp was also made giving an efficiency of about 18 l-p-w -using the regular electrode. This electrode in being consumed gives -off fumes, so the lamp has a chimney through its body to carry them -off. Some of the fumes condense, leaving a fine powder, iron oxide, in -the form of rust. The consumption of the positive (copper) electrode -is very slow, which is opposite to that of carbon arc lamps on direct -current. The arc flame is brightest near the negative (iron tube) -electrode and decreases in brilliancy and volume as it nears the -positive (copper) electrode. - -[Illustration: DIAGRAM OF SERIES MAGNETITE ARC LAMP. - -The method of control, entirely different from that of other arc lamps, -was invented by Halvorson to meet the peculiarities of this arc.] - -The peculiarities of the arc are such that Halvorson invented an -entirely new principle of control. The electrodes are normally apart. -In starting, they are drawn together by a starting magnet with -sufficient force to dislodge the slag which forms on the negative -electrode and which becomes an insulator when cold. Current then flows -through the electrodes and through a series magnet which pulls up a -solenoid breaking the circuit through the starting magnet. This allows -the lower electrode to fall a fixed distance, about seven-eighths of -an inch, drawing the arc, whose voltage is then about 72 volts. As the -negative electrode is consumed, the length and voltage of the arc -increases when a magnet, in shunt with the arc, becomes sufficiently -energized to close the contacts in the circuit of the starting magnet -causing the electrode to pick up and start off again. - - - - -MERCURY ARC RECTIFIER FOR MAGNETITE ARC LAMPS - - -[Illustration: MERCURY ARC RECTIFIER TUBE FOR SERIES MAGNETITE ARC -LAMPS, 1902. - -The mercury arc converted the alternating constant current into direct -current required by the magnetite lamp.] - -As the magnetite arc requires direct current for its operation, the -obvious way to supply a direct constant current for series circuits -is to rectify, by means of the mercury arc, the alternating current -obtained from a constant current transformer. The terminals of the -movable secondary coil of the constant current transformer are -connected to the two arms of the rectifier tube. One end of the series -circuit is connected to the center of the secondary coil. The other -end of the series circuit is connected to a reactance which in turn -is connected to the pool of mercury in the bottom of the rectifier -tube. One-half of the cycle of the alternating current goes from the -secondary coil to one arm of the rectifier tube through the mercury -vapor, the mercury arc having already been started by a separate -starting electrode. It then goes to the pool of mercury, through -the reactance and through the series circuit. The other half cycle -of alternating current goes to the other arm of the rectifier tube, -through the mercury vapor, etc., and through the series circuit. Thus a -pulsating direct current flows through the series circuit, the magnetic -action of the reactance coil making the pulsations of current overlap -each other, which prevents the mercury arc from going out. - -[Illustration: EARLY MERCURY ARC RECTIFIER INSTALLATION.] - - - - -INCANDESCENT LAMP DEVELOPMENTS, 1894–1904 - - -With the development of a waterproof base in 1900, by the use of a -waterproof cement instead of plaster of Paris to fasten the base to -the bulb, porcelain at first and later glass being used to insulate -the terminals of the base from each other, lamps could be exposed to -the weather and give good results. Electric sign lighting therefore -received a great stimulus, and lamps as low as 2 candlepower for 110 -volts were designed for this purpose. Carbon lamps with concentrated -filaments were also made for stereoptican and other focussing purposes. -These lamps were made in sizes from 20 to 100 candlepower. The arc lamp -was more desirable for larger units. - -The dry battery was made in small units of 2, 3 and 5 cells, so that -lamps of about ⅛ to 1 candlepower were made for 2½, 3½ and 6½ volts, -for portable flashlights. It was not however until the tungsten -filament was developed in 1907 that these flashlights became as popular -as they now are. For ornamental lighting, lamps were supplied in round -and tubular bulbs, usually frosted to soften the light. - -[Illustration: THE MOORE TUBE LIGHT, 1904. - -This consisted of a tube about 1¾ inches in diameter and having a -length up to 200 feet, in which air at about one thousandth part -of atmospheric pressure was made to glow by a very high voltage -alternating current.] - - - - -THE MOORE TUBE LIGHT - - -Geissler, a German, discovered sixty odd years ago, that a high voltage -alternating current would cause a vacuum tube to glow. This light -was similar to that obtained by Hawksbee over two hundred years ago. -Geissler obtained his high voltage alternating current by a spark -coil, which consisted of two coils of wire mounted on an iron core. -Current from a primary battery passed through the primary coil, and -this current was rapidly interrupted by a vibrator on the principle of -an electric bell. This induced an alternating current of high voltage -in the secondary coil as this coil had a great many more turns than -the primary coil had. Scientists found that about 70 per cent of the -electrical energy put into the Geissler tube was converted into the -actual energy in the light given out. - -In 1891 Mr. D. McFarlan Moore, an American, impressed with the fact -that only one-half of one per cent of the electrical energy put into -the carbon-incandescent lamp came out in the form of light, decided to -investigate the possibilities of the vacuum tube. After several years -of experiments and the making of many trial lamps, he finally, in 1904, -made a lamp that was commercially used in considerable numbers. - -[Illustration: DIAGRAM OF FEEDER VALVE OF MOORE TUBE. - -As the carbon terminals inside the tube absorbed the very slight -amount of gas in the tube, a feeder valve allowed gas to flow in the -tube, regulating the pressure to within one ten thousandth part of -an atmosphere above and below the normal extremely slight pressure -required.] - -The first installation of this form of lamp was in a hardware store -in Newark, N. J. It consisted of a glass tube 1¾ inches in diameter -and 180 feet long. Air, at a pressure of about one-thousand part of -an atmosphere, was in the tube, from which was obtained a pale pink -color. High voltage (about 16,000 volts) alternating current was -supplied by a transformer to two carbon electrodes inside the ends of -the tube. The air had to be maintained within one ten-thousandth part -of atmospheric pressure above and below the normal of one-thousandth, -and as the rarefied air in the tube combined chemically with the carbon -electrodes, means had to be devised to maintain the air in the tube at -this slight pressure as well as within the narrow limits required. - -This was accomplished by a piece of carbon through which the air could -seep, but if covered with mercury would make a tight seal. As the air -pressure became low, an increased current would flow through the tube, -the normal being about a tenth of an ampere. This accordingly increased -the current flowing through the primary coil of the transformer. In -series with the primary coil was an electro-magnet which lifted, as the -current increased, a bundle of iron wires mounted in a glass tube which -floated in mercury. The glass tube, rising, lowered the height of the -mercury, uncovering a carbon rod cemented in a tube connecting the main -tube with the open air. Thus air could seep through this carbon rod -until the proper amount was fed into the main tube. When the current -came back to normal the electro-magnet lowered the floating glass tube -which raised the height of the mercury and covered the carbon rod, thus -shutting off the further supply of air. - -As there was a constant loss of about 400 watts in the transformer, -and an additional loss of about 250 watts in the two electrodes, the -total consumption of the 180-foot tube was about 2250 watts. Nitrogen -gas gave a yellow light, which was more efficient and so was later -used. On account of the fixed losses in the transformer and electrodes -the longer tubes were more efficient, though they were made in various -sizes of from 40 to 200 feet. The 200-foot tube, with nitrogen, had an -efficiency of about 10 lumens per watt. Nitrogen gas was supplied to the -tube by removing the oxygen from the air used. This was accomplished by -passing the air over phosphorous which absorbed the oxygen. - -Carbon dioxide gas (CO_{2}) gave a pure white light but at about -half the efficiency of nitrogen. The gas was obtained by allowing -hydrochloric acid to come in contact with lumps of marble (calcium -carbonate) which set free carbon dioxide and water vapor. The latter -was absorbed by passing the gas through lumps of calcium chloride. The -carbon dioxide tube on account of its daylight color value, made an -excellent light under which accurate color matching could be done. A -short tube is made for this purpose and this is the only use which the -Moore tube now has, owing to the more efficient and simpler tungsten -filament incandescent lamp. - - - - -THE OSMIUM LAMP - - -Dr. Auer von Welsbach, the German scientist who had produced the -Welsbach gas mantle, invented an incandescent electric lamp having a -filament of the metal osmium. It was commercially introduced in Europe -in 1905 and a few were sold, but it was never marketed in this country. -It was generally made for 55 volts, two lamps to burn in series on -110-volt circuits, gave about 25 candlepower and had an initial -efficiency of about 5½ lumens per watt. It had a very fair maintenance -of candlepower during its life, having an average efficiency of about -5 l-p-w. Osmium is a very rare and expensive metal, usually found -associated with platinum, and is therefore very difficult to obtain. -Burnt out lamps were therefore bought back in order to obtain a supply -of osmium. It is also a very brittle metal, so that the lamps were -extremely fragile. - -[Illustration: OSMIUM LAMP, 1905. - -This incandescent lamp was used in Europe for a few years, but was -impractical to manufacture in large quantities as osmium is rarer and -more expensive than platinum.] - - - - -THE GEM LAMP - - -Dr. Willis R. Whitney, of Schenectady, N. Y., had invented an -electrical resistance furnace. This consisted of a hollow carbon tube, -packed in sand, through which a very heavy current could be passed. -This heated the tube to a very high temperature, the sand preventing -the tube from oxidizing, so that whatever was put inside the tube -could be heated to a very high heat. Among his various experiments, -he heated some carbon filaments and found that the high temperature -changed their resistance “characteristic” from negative to positive. -The ordinary carbon filament has a resistance when hot that is less -than when it is cold, which was reversed after heating it to the high -temperature Dr. Whitney was able to obtain. These filaments were made -into lamps for 110-volt service and it was found that they could -be operated at an efficiency of 4 lumens per watt. The lamps also -blackened less than the regular carbon lamp throughout their life. - -[Illustration: GEM LAMP, 1905. - -This incandescent lamp had a graphitized carbon filament obtained by -the heat of an electric furnace, so that it could be operated at 25 per -cent higher efficiency than the regular carbon lamp. This lamp is in -the exhibit of Edison lamps in the Smithsonian Institution.] - -This lamp was put on the market in 1905 and was called the Gem or -metallized carbon filament lamp as such a carbon filament had a -resistance characteristic similar to metals. At first it had two single -hair pin filaments in series which in 1909 were changed to a single -loop filament like the carbon lamp. - -In 1905 the rating of incandescent lamps was changed from a candlepower -to a wattage basis. The ordinary 16-candlepower carbon lamp consumed -50 watts and was so rated. The 50-watt Gem lamp gave 20 candlepower, -both candlepower ratings being their mean candlepower in a horizontal -direction. The Gem lamp was made for 110-volt circuits in sizes from -40 to 250 watts. The 50-watt size was the most popular, many millions -of which were made before the lamp disappeared from use in 1918. The -lamp was not quite as strong as the carbon lamp. Some Gem lamps for -series circuits were also made, but these were soon superseded by the -tungsten-filament lamp which appeared in 1907. - - - - -THE TANTALUM LAMP - - -[Illustration: TANTALUM LAMP, 1906. - -The tantalum filament could be operated at 50 per cent greater -efficiency than that of the regular carbon incandescent lamp. This lamp -is in the exhibit of Edison lamps in the Smithsonian Institution.] - -Dr. Werner von Bolton, a German physicist, made an investigation of -various materials to see if any of them were more suitable than carbon -for an incandescent-lamp filament. After experimenting with various -metals, tantalum was tried. Tantalum had been known to science for -about a hundred years. Von Bolton finally obtained some of the pure -metal and found it to be ductile so that it could be drawn out into a -wire. As it had a low specific resistance, the wire filament had to -be much longer and thinner than the carbon filament. A great number -of experimental lamps were made so that it was not until 1906 that -the lamp was put on the market in this country. It had an initial -efficiency of 5 lumens per watt and a good maintenance of candle power -throughout its life, having an average efficiency of about 4¼ l-p-w. -The usual sizes of lamps were 40 and 80 watts giving about 20 and 40 -candlepower respectively. It was not quite as strong as the carbon -lamp, and on alternating current the wire crystallized more rapidly, -so that it broke more easily, giving a shorter life than on direct -current. It disappeared from use in 1913. - - - - -INVENTION OF THE TUNGSTEN LAMP - - -Alexander Just and Franz Hanaman in 1902 were laboratory assistants -to the Professor of Chemistry in the Technical High School in Vienna. -Just was spending his spare time in another laboratory in Vienna, -attempting to develop a boron incandescent lamp. In August of that year -he engaged Hanaman to aid him in his work. They conceived the idea of -making a lamp with a filament of tungsten and for two years worked on -both lamps. The boron lamp turned out to be a failure. Their means -were limited; Hanaman’s total income was $44 per month and Just’s was -slightly more than this. In 1903 they took out a German patent on a -tungsten filament, but the process they described was a failure because -it produced a filament containing both carbon and tungsten. The carbon -readily evaporated and quickly blackened the bulb when they attempted -to operate the filament at an efficiency higher than that possible with -the ordinary carbon filament. Finally in the latter part of the next -year (1904) they were able to get rid of the carbon and produced a pure -tungsten filament. - -Tungsten had been known to chemists for many years by its compounds, -its oxides and its alloys with steel, but the properties of the pure -metal were practically unknown. It is an extremely hard and brittle -metal and it was impossible at that time to draw it into a wire. Just -and Hanaman’s process of making a pure tungsten filament consisted of -taking tungsten oxide in the form of an extremely fine powder, reducing -this to pure tungsten powder by heating it while hydrogen gas passed -over it. The gas combined with the oxygen of the oxide, forming water -vapor which was carried off, leaving the tungsten behind. - -The tungsten powder was mixed with an organic binding material, and -the paste was forced by very high pressure through a hole drilled in -a diamond. This diamond die was necessary because tungsten, being so -hard a substance, would quickly wear away any other kind of die. The -thread formed was cut into proper lengths, bent the shape of a hair -pin and the ends fastened to clamps. Current was passed through the -hair pin in the presence of hydrogen gas and water vapor. The current -heated the hair pin, carbonized the organic binding material in it, the -carbon then combining with the moist hydrogen gas, leaving the tungsten -particles behind. These particles were sintered together by the heat, -forming the tungsten filament. Patents were applied for in various -countries, the one in the United States on July 6, 1905. - -The two laboratory assistants in 1905 finally succeeded in getting -their invention taken up by a Hungarian lamp manufacturer. By the end -of the year lamps were made that were a striking success for they could -be operated at an efficiency of 8 lumens per watt. They were put on -the American market in 1907, the first lamp put out being the 100-watt -size for 110-volt circuits. This was done by mounting several hair pin -loops in series to get the requisite resistance, tungsten having a -low specific resistance. The issue of the American patent was delayed -owing to an interference between four different parties, each claiming -to be the inventor. After prolonged hearings, one application having -been found to be fraudulent, the patent was finally granted to Just and -Hanaman on February 27, 1912. - -[Illustration: TUNGSTEN LAMP, 1907. - -The original 100 watt tungsten lamp was nearly three times as efficient -as the carbon lamp, but its “pressed” filament was very fragile. This -lamp is in the exhibit of Edison lamps in the Smithsonian Institution.] - -This “pressed” tungsten filament was quite fragile, but on account of -its relatively high efficiency compared with other incandescent lamps, -it immediately became popular. Soon after its introduction it became -possible to make finer filaments so that lamps for 60, 40 and then 25 -watts for 110-volt circuits were made available. Sizes up to 500 watts -were also made which soon began to displace the enclosed carbon arc -lamp. Lamps were also made for series circuits in sizes from 32 to 400 -candlepower. These promptly displaced the carbon and Gem series lamps. -The high efficiency of the tungsten filament was a great stimulus to -flashlights which are now sold by the millions each year. The lighting -of railroad cars, Pullmans and coaches, with tungsten lamps obtaining -their current from storage batteries, soon superseded the gas light -formerly used. In some cases, a dynamo, run by a belt from the car -axle, kept these batteries charged. - -[Illustration: DRAWN TUNGSTEN WIRE LAMP, 1911. - -Scientists had declared it impossible to change tungsten from a brittle -to ductile metal. This, however, was accomplished by Dr. Coolidge, and -drawn tungsten wire made the lamp very sturdy. This lamp is in the -exhibit of Edison lamps in the Smithsonian Institution.] - - - - -DRAWN TUNGSTEN WIRE - - -After several years of patient experiment, Dr. William D. Coolidge -in the research laboratory of a large electrical manufacturing -company at Schenectady, N. Y., invented a process for making tungsten -ductile, a patent for which was obtained in December, 1913. Tungsten -had heretofore been known as a very brittle metal, but by means of -this process it became possible to draw it into wire. This greatly -simplified the manufacture of lamps and enormously improved their -strength. Such lamps were commercially introduced in 1911. - -With drawn tungsten wire it was easier to coil and therefore -concentrate the filament as required by focusing types of lamps. The -automobile headlight lamp was among the first of these, which in 1912 -started the commercial use of electric light on cars in place of oil -and acetylene gas. On street railway cars the use of tungsten lamps, -made possible on this severe service by the greater sturdiness of -the drawn wire, greatly improved their lighting. Furthermore, as the -voltage on street railway systems is subject to great changes, the -candlepower of the tungsten filament has the advantage of varying but -about half as much as that of the carbon lamp on fluctuating voltage. - -[Illustration: QUARTZ MERCURY VAPOR LAMP, 1912. - -The mercury arc if enclosed in quartz glass can be operated at much -higher temperature and therefore greater efficiency. The light is -still deficient in red but gives a considerable amount of ultra-violet -rays which kill bacteria and are very dangerous to the eye. They can, -however, be absorbed by a glass globe. The lamp is not used as an -illuminant in this country, but is valuable for use in the purification -of water.] - - - - -THE QUARTZ MERCURY VAPOR ARC LAMP - - -By putting a mercury arc in a tube made of quartz instead of glass, -it can be operated at a much higher temperature and thereby obtain a -greater efficiency. Such a lamp, however, is still largely deficient in -red rays, and it gives out a considerable amount of ultra-violet rays. -These ultra-violet rays will kill bacteria and the lamp is being used -to a certain extent for such purpose as in the purification of water. -These rays are very dangerous to the eyes, but they are absorbed by -glass, so as an illuminant, a glass globe must be used on the lamp. -These lamps appeared in Europe about 1912 but were never used to any -extent in this country as an illuminant. They have an efficiency of -about 26 lumens per watt. Quartz is very difficult to work, so the cost -of a quartz tube is very great. The ordinary bunsen gas flame is used -with glass, but quartz will only become soft in an oxy-hydrogen or -oxy-acetylene flame. - -[Illustration: GAS FILLED TUNGSTEN LAMP, 1913. - -By operating a coiled filament in an inert gas, Dr. Langmuir was able -to greatly increase its efficiency, the gain in light by the higher -temperature permissible, more than offsetting the loss of heat by -convection of the gas. This lamp is in the exhibit of Edison lamps in -the Smithsonian Institution.] - - - - -THE GAS-FILLED TUNGSTEN LAMP - - -The higher the temperature at which an incandescent lamp filament can -be operated, the more efficient it becomes. The limit in temperature is -reached when the material begins to evaporate rapidly, which blackens -the bulb. The filament becoming thinner more quickly, thus rupturing -sooner, shortens the life. If, therefore, the evaporating temperature -can by some means be slightly raised, the efficiency will be greatly -improved. This was accomplished by Dr. Irving Langmuir in the research -laboratories at Schenectady, N. Y., by operating a tungsten filament -in an inert gas. Nitrogen was first used. The gas circulating in the -bulb has the disadvantage of conducting heat away from the filament -so that the filament was coiled. This presented a smaller surface to -the currents of gas and thereby reduced this loss. The lamps were -commercially introduced in 1913 and a patent was granted in April, 1916. - -[Illustration: GAS FILLED TUNGSTEN LAMP, 1923. - -This is the form of the lamp as at present made. For 110-volt circuits -the sizes range from 50 to 1000 watts.] - -An increased amount of electrical energy is required in these lamps -to offset the heat being conducted away by the gas. This heat loss is -minimized in a vacuum lamp, the filament tending to stay hot on the -principle of the vacuum bottle. This loss in a gas filled lamp becomes -relatively great in a filament of small diameter, as the surface in -proportion to the volume of the filament increases with decreasing -diameters. Hence there is a point where the gain in temperature is -offset by the heat loss. The first lamps made were of 750 and 1000 -watts for 110-volt circuits. Later 500- and then 400-watt lamps were -made. The use of argon gas, which has a poorer heat conductivity than -nitrogen, made it possible to produce smaller lamps, 50-watt gas-filled -lamps for 110-volt circuits now being the smallest available. In the -present state of the art, a vacuum lamp is more efficient than a -gas-filled lamp having a filament smaller than one consuming about half -an ampere. Thus gas-filled lamps are not now practicable much below 100 -watts for 220 volts, 50 watts for 110 volts, 25 watts for 60 volts, 15 -watts for 30 volts, etc. - -From the foregoing it will be seen that the efficiency of these lamps -depends largely on the diameter of the filament. There are other -considerations, which also apply to vacuum lamps, that affect the -efficiency. Some of these are: the number of anchors used, as they -conduct heat away; in very low voltage lamps having short filaments the -relative amount of heat conducted away by the leading-in wires becomes -of increasing importance, etc. The 1000-watt lamp for 110-volt circuits -is now made for nearly 20½ lumens per watt; the 50-watt lamp a little -over 10 l-p-w. - -The advent of the tungsten filament and especially the gas-filled -lamp sounded the doom of all other electric illuminants except the -magnetite and mercury arc lamps. All other incandescent lamps have now -practically disappeared. The flame arc as well as the enclosed carbon -arc lamp are hardly ever seen. The simplicity of the incandescent -lamp, its cleanliness, low first cost, low maintenance cost and high -efficiency of the tungsten filament have been the main reasons for its -popularity. - - - - -TYPES AND SIZES OF TUNGSTEN LAMPS NOW MADE - - -There are about two hundred different types and sizes of tungsten -filament lamps now standard for various kinds of lighting service. For -110-volt service, lamps are made in sizes from 10 to 1000 watts. Of -the smaller sizes, some are made in round and tubular-shaped bulbs for -ornamental lighting. In addition there are the candelabra lamps used -in ornamental fixtures. Twenty-five- to five hundred-watt lamps are -made with bulbs of special blue glass to cut out the excess of red and -yellow rays and thus produce a light approximating daylight. - -For 220-volt service lamps are made in sizes of from 25 to 1000 watts. -For sign lighting service, 5-watt lamps of low voltage are made for -use on a transformer located near the sign to reduce the 110 volts -alternating current to that required by the lamps. Lamps are made from -5 to 100 watts for 30-volt service, such as is found in train lighting -and in gas engine driven dynamo sets used in rural homes beyond the -reach of central station systems. Concentrated filament lamps are -made for stereopticon and motion picture projection, floodlighting, -etc., in sizes from 100 to 1000 watts, for street railway headlights -in sizes below 100 watts and for locomotive headlights in sizes from -100 to 250 watts. For series circuits, used in street lighting, lamps -are made from 60 to 2500 candlepower. Miniature lamps cover those for -flashlight, automobile, Christmas-tree, surgical and dental services, -etc. They range, depending on the service, from ½ to 21 candlepower, -and in voltage from 2½ to 24. - -[Illustration: STANDARD TUNGSTEN LAMPS, 1923. - -This illustrates some of the two hundred different lamps regularly -made.] - - - - -STANDARD VOLTAGES - - -Mention has been made of 110-volt service, 220-volt service, etc. -In the days of the carbon incandescent lamp it was impossible to -manufacture all lamps for an exact predetermined voltage. The popular -voltage was 110, so lighting companies were requested in a number of -instances to adjust their service to some voltage other than 110. They -were thus able to utilize the odd voltage lamps manufactured, and this -produced a demand for lamps of various voltages from 100 to 130. Arc -lamps had a resistance (reactance on alternating current) that was -adjustable for voltages between 100 and 130. - -Similarly a demand was created for lamps of individual voltages of -from 200 to 260. The 200- to 260-volt range has simmered down to -220, 230, 240 and 250 volts. These lamps are not as efficient as the -110-volt type and their demand is considerably less, as the 110-volt -class of service for lighting is, with the exception of England, -almost universal. Thus 110-volt service means 100 to 130 volts in -contra-distinction to 200 to 260 volts, etc. The drawn tungsten wire -filament made it possible to accurately predetermine the voltage of -the lamp, so now that the carbon incandescent lamp is a thing of the -past, there is no need for so many different voltages. Several years -ago standard voltages of 110, 115 and 120 were recommended for adoption -by all the electrical societies in the United States, and practically -all central stations have now changed their service to one of these -voltages. - - - - -COST OF INCANDESCENT ELECTRIC LIGHT - - -In the early ’80’s current was expensive, costing a consumer on the -average about twenty cents per kilowatt hour. The cost has gradually -come down and the general average rate for which current is sold for -lighting purposes is now about 4½ cents. During the period 1880 to 1905 -the average efficiency of carbon lamps throughout their life increased -from about one to over 2¾ lumens per watt and their list price -decreased from one dollar to twenty cents. The average amount of light -obtained for one cent at first was about five candlepower hours and in -1904 it was increased to over thirty-six at the average rate then in -effect. The next year with the more efficient Gem lamp 44 candle-hours -could be had for one cent. In 1906 the amount was increased to 50 with -the tantalum lamp and with the tungsten lamp in 1907, even at its high -price of $1.50, the amount was further increased to 63. Since then -the average cost of current has been reduced but slightly, but the -efficiency of the tungsten lamp has materially increased and its cost -reduced so that it is now possible to obtain, with the ordinary 40-watt -lamp 170 candle-hours for a cent. If the gas-filled tungsten lamp were -used the amount of light now obtained for a cent would depend upon the -size, which, for the 1000-watt lamp, would be 382 candle-hours. - - - - -STATISTICS REGARDING THE PRESENT DEMAND FOR LAMPS - - -In the United States there are about 350 million incandescent and -about two hundred thousand magnetite arc lamps now (1923) in use. -They are increasing about 10 per cent each year. The annual demand -for incandescent lamps for renewals and new installations is over 200 -millions, exclusive of miniature lamps. The use of incandescent lamps -in all other countries put together is about equal that in the U. S. - -The average candlepower of standard lighting lamps has increased from -16, which prevailed during the period prior to 1905, to over 60. The -average wattage has not varied much during the past twenty-odd years, -the average lamp now consuming about 55 watts. This indicates that the -public is utilizing the improvement in lamp efficiency by increased -illumination. The present most popular lamp is the 40-watt size which -represents 20 per cent of the total demand. Second in demand is the -25-watt at 18 per cent and third, the 50-watt at 15 per cent of the -total in numbers. While the aggregate demand of all the gas-filled -tungsten lamps is a little over 20 per cent in numbers, they represent, -on account of their greater efficiency and wattage, over half the -amount of total candlepower used. In the United States about 85 per -cent of all lamps are for the 110-volt range. About 5 per cent for 220 -volts, 2 per cent for street series lighting, 3 per cent for street -railway and 5 per cent for trainlighting and miscellaneous classes of -service. - - - - -SELECTED BIBLIOGRAPHY - - - ALGLAVE AND BOULARD, “The Electric Light,” translated by T. - O’Connor Sloane, edited by C. M. Lungren, D. Appleton & Co., - New York, 1884. - - BARHAM, G. BASIL, “The Development of the Incandescent Electric - Lamp,” Scott Greenwood & Son, London, 1912. - - DREDGE, JAMES, “Electric Illumination,” 2 vols., John Wiley & Sons, - New York, 1882. - - DURGIN, WILLIAM A., “Electricity--Its History and Development,” - A. C. McClurg & Co., Chicago, 1912. - - DYER & MARTIN, “Edison, His Life and Inventions,” 2 vols., Harper & - Bros., New York, 1910. - - GUILLEMIN, AMEDEE, “Electricity and Magnetism,” edited by Silvanus - P. Thompson, McMillan & Co., London, 1891. - - HOUSTON, EDWIN J., “Electricity One Hundred Years ago and To-day,” - The W. J. Johnston Co., New York, 1894. - - HOUSTON AND KENNELLY, “Electric Arc Lighting,” McGraw Publishing - Co., New York, 1906. - - HUTCHINSON, ROLLIN W., JR., “High Efficiency Electrical Illuminants - and Illumination,” John Wiley & Sons, New York, 1911. - - MAIER, JULIUS, “Arc and Glow Lamps,” Whittaker & Co., London, 1886. - - POPE, FRANKLIN LEONARD, “Evolution of the Electric Incandescent - Lamp,” Boschen & Wefer, New York, 1894. - - SOLOMON, MAURICE, “Electric Lamps,” D. Van Nostrand Co., New York, - 1908. - - - - -Transcriber’s Notes - - -Punctuation, hyphenation, and spelling were made consistent when a -predominant preference was found in the original book; otherwise they -were not changed. - -Simple typographical errors were corrected; unbalanced quotation -marks were remedied when the change was obvious, and otherwise left -unbalanced. - -Illustrations in this eBook have been positioned between paragraphs. 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