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diff --git a/39785-h/39785-h.htm b/39785-h/39785-h.htm new file mode 100644 index 0000000..be5743d --- /dev/null +++ b/39785-h/39785-h.htm @@ -0,0 +1,2892 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> + <head> + <meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1" /> + <meta http-equiv="Content-Style-Type" content="text/css" /> + <title> + The Project Gutenberg eBook of Tunnel Engineering—A Museum Treatment, by Robert M. 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A Museum Treatment, by +Robert M. Vogel + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Tunnel Engineering. A Museum Treatment + +Author: Robert M. Vogel + +Release Date: May 24, 2012 [EBook #39785] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK TUNNEL ENGINEERING *** + + + + +Produced by Chris Curnow, Tom Cosmas, Joseph Cooper and +the Online Distributed Proofreading Team at +http://www.pgdp.net + + + + + + +</pre> + + +<div class="fig_center" style="width: 242px; margin-bottom:2em;"> +<a name="cover" id="cover"></a> +<img src="images/cover.jpg" width="312" height="435" alt="" title="" /> +</div> + +<div class="trans_notes"> +<p>This is Paper 41 from the <i>Smithsonian Institution United States +National Museum Bulletin 240</i>, comprising Papers 34-44, which will +also be available as a complete e-book.</p> + +<p>The front material, introduction and relevant index entries from +the <i>Bulletin</i> are included in each single-paper e-book.</p> + +<p>For most images, clicking on them will open a larger version.</p> +</div> + +<p class="caption1nc tdr">SMITHSONIAN INSTITUTION<br /> +UNITED STATES NATIONAL MUSEUM<br /> +BULLETIN 240</p> + +<div class="fig_right"> + <img src="images/i_002b.png" width="172" height="237" alt="Smithsonian Press Logo" title="" /> +</div> + +<p class="tdr pmb4" style="clear: both;">SMITHSONIAN PRESS</p> + +<div class="center" style="font-size:150%;"> +MUSEUM OF HISTORY AND TECHNOLOGY<br /> + +<div class="tdl p0 pmt4 pmb4" style="padding-left:2em; line-height:150%; margin-left:20%"> +<span class="smcap pmb2" style="font-size:150%;">Contributions<br /> +From the<br /> +Museum<br /> +of History and<br /> +Technology</span><br /> +<br /> +<i>Papers 34-44<br /> +On Science and Technology</i> +</div> + +<span class="p0 pmt2">SMITHSONIAN INSTITUTION · WASHINGTON, D.C. 1966</span> +</div> + +<hr class="chap" /> + +<p class="center larger"><i>Publications of the United States National Museum</i></p> + +<p>The scholarly and scientific publications of the United States National Museum +include two series, <i>Proceedings of the United States National Museum</i> and <i>United States +National Museum Bulletin</i>.</p> + +<p>In these series, the Museum publishes original articles and monographs dealing +with the collections and work of its constituent museums—The Museum of Natural +History and the Museum of History and Technology—setting forth newly acquired +facts in the fields of anthropology, biology, history, geology, and technology. Copies +of each publication are distributed to libraries, to cultural and scientific organizations, +and to specialists and others interested in the different subjects.</p> + +<p>The <i>Proceedings</i>, begun in 1878, are intended for the publication, in separate +form, of shorter papers from the Museum of Natural History. These are gathered +in volumes, octavo in size, with the publication date of each paper recorded in the +table of contents of the volume.</p> + +<p>In the <i>Bulletin</i> series, the first of which was issued in 1875, appear longer, separate +publications consisting of monographs (occasionally in several parts) and volumes +in which are collected works on related subjects. <i>Bulletins</i> are either octavo or +quarto in size, depending on the needs of the presentation. Since 1902 papers relating +to the botanical collections of the Museum of Natural History have been +published in the <i>Bulletin</i> series under the heading <i>Contributions from the United States +National Herbarium</i>, and since 1959, in <i>Bulletins</i> titled “Contributions from the Museum +of History and Technology,” have been gathered shorter papers relating to the collections +and research of that Museum.</p> + +<p>The present collection of Contributions, Papers 34-44, comprises Bulletin 240. +Each of these papers has been previously published in separate form. The year of +publication is shown on the last page of each paper.</p> + +<p class="tdr"><span class="smcap">Frank A. Taylor</span><br /> +<em>Director, United States National Museum</em></p> + +<hr class="full" /> + +<p><span class="pagenum"><a name="Page_201" id="Page_201">[201]</a></span><br /> +<a name="Paper_41" id="Paper_41"></a></p> + +<p class="tdr" style="font-size:1.5em; line-height:150%;"> +<span class="smcap">Contributions from <br /> +The Museum of History and Technology.</span><br /> +<span class="smcap">Paper</span> 41<br /> +<br /> +<br /> +<span class="smcap">Tunnel Engineering—A Museum Treatment</span></p> + +<p class="tdr" style="font-size:1.5em;;"><i>Robert M. Vogel</i></p> + +<table class="pmt4 pmb4" style="width:100%;" summary="ToC"> +<tr> + <td class="tdr" style="padding-bottom:2em;"><a href="#Introduction">INTRODUCTION</a></td> + <td class="tdr vtop">203</td> +</tr> +<tr> + <td class="tdr" style="padding-bottom:2em;"><a href="#Rock_Tunneling">ROCK TUNNELING</a></td> + <td class="tdr vtop" style="width:3em">206</td> +</tr> +<tr> + <td class="tdr" style="padding-bottom:2em;"><a href="#Soft-Ground_Tunneling">SOFT-GROUND TUNNELING</a></td> + <td class="tdr vtop">215</td> +</tr> +<tr> + <td class="tdr" style="padding-bottom:2em;"><a href="#BIBLIOGRAPHY">BIBLIOGRAPHY</a></td> + <td class="tdr vtop">239</td> +</tr> +<tr> + <td class="tdr" style="padding-bottom:2em;"><a href="#FOOTNOTES">FOOTNOTES</a></td> + <td></td> +</tr> +<tr> + <td class="tdr" style="padding-bottom:2em;"><a href="#INDEX">INDEX</a></td> + <td></td> +</tr> +</table> + +<p><span class="pagenum"><a name="Page_202" id="Page_202">[202]</a></span></p> +<div class="fig_center" style="width: 537px;"> +<a name="Fig_41_1" id="Fig_41_1"></a> +<a href="images/fig_41_1_lrg.png"><img src="images/fig_41_1.png" width="537" height="610" alt="" /></a> +<p class="fig_caption pmb4">Figure 1.—<span class="smcap">Mining by early European civilizations</span>, +using fire setting and hand chiseling to break out ore and rock. +MHT model—¾" scale. (Smithsonian photo 49260-H.)</p> +</div> + +<p><span class="pagenum"><a name="Page_203" id="Page_203">[203]</a></span></p> +<p class="caption2nc tdr pmb2"><i>Robert M. Vogel</i></p> + +<p class="caption1"><a name="TUNNEL_ENGINEERING_A" id="TUNNEL_ENGINEERING_A"></a> +TUNNEL ENGINEERING—A MUSEUM TREATMENT</p> + +<blockquote><p><i>During the years from 1830 to 1900, extensive developments took +place in the field of tunneling, which today is an important, +firmly established branch of civil engineering. This paper offers +a picture of its growth from the historical standpoint, based on +a series of models constructed for the Hall of Civil Engineering +in the new Museum of History and Technology. The eight +models described highlight the fundamental advances which have +occurred between primitive man’s first systematic use of fire for +excavating rock in mining, and the use in combination of compressed +air, an iron lining, and a movable shield in a subaqueous +tunnel at the end of the 19th century.</i></p> + +<p><span class="smcap">The Author</span>: <i>Robert M. Vogel is curator of heavy machinery +and civil engineering, in the Smithsonian Institution’s Museum +of History and Technology.</i></p></blockquote> + +<p class="caption2"><a name="Introduction" +id="Introduction"></a>Introduction</p> + +<div class="dropcap">W</div> +<p class="p0">ith few exceptions, civil engineering is a field +in which the ultimate goal is the assemblage of +materials into a useful structural form according to a +scientifically derived plan which is based on various +natural and man-imposed conditions. This is true +whether the result be, for example, a dam, a building, +a bridge, or even the fixed plant of a railroad. However, +one principal branch of the field is based upon +an entirely different concept. In the engineering of +tunnels the utility of the “structure” is derived not +from the bringing together of elements but from the +separation of one portion of naturally existing material +from another to permit passage through a former +barrier.</p> + +<p>In tunneling hard, firm rock, this is practically +the entire compass of the work: breaking away the +rock from the mother mass, and, coincidently, removing +it from the workings. The opposite extreme +in conditions is met in the soft-ground tunnel, driven +through material incapable of supporting itself above +<span class="pagenum"><a name="Page_204" id="Page_204">[204]</a></span> +the tunnel opening. Here, the excavation of the +tunneled substance is of relatively small concern, +eclipsed by the problem of preventing the surrounding +material from collapsing into the bore.</p> + +<div class="fig_center" style="width: 547px;"> +<a name="Fig_41_2" id="Fig_41_2"></a> +<a href="images/fig_41_2_lrg.png"> +<img src="images/fig_41_2.png" width="547" height="155" alt="" /></a> +<p class="fig_caption">Figure 2.—<span class="smcap">Hoosac Tunnel. Method of working early sections</span> +of the project; blast holes drilled by hand jacking. MHT +model—½" scale. (Smithsonian photo 49260-L.)</p> +</div> + +<p>In one other principal respect does tunnel engineering +differ widely from its collateral branches of +civil engineering. Few other physical undertakings +are approached with anything like the uncertainty +attending a tunnel work. This is even more true in +mountain tunnels, for which test borings frequently +cannot be made to determine the nature of the +material and the geologic conditions which will be +encountered.</p> + +<p>The course of tunnel work is not subject to an overall +preliminary survey; the engineer is faced with not +only the inability to anticipate general contingencies +common to all engineering work, but with the peculiar +and often overwhelming unpredictability of the +very basis of his work.</p> + +<p>Subaqueous and soft-ground work on the other +hand, while still subject to many indeterminates, is +now far more predictable than during its early history, +simply because the nature of the adverse condition +prevailing eventually was understood to be quite +predictable. The steady pressures of earth and water +to refill the excavated area are today overcome with +relative ease and consistency by the tunneler.</p> + +<p>In tunneling as in no other branch of civil engineering +did empiricism so long resist the advance of scientific +theory; in no other did the “practical engineer” +remain to such an extent the key figure in establishing +the success or failure of a project. The Hoosac Tunnel, +after 25 years of legislative, financial, and technical +difficulties, in 1875 was finally driven to successful +completion only by the efforts of a group who, while +in the majority were trained civil engineers, were to +an even greater extent men of vast practical ability, +more at home in field than office.</p> + +<p>DeWitt C. Haskin (see <a href="#Haskin">p. 234</a>), during the inquest +that followed the death of a number of men in a +blowout of his pneumatically driven Hudson River +Tunnel in 1880, stated in his own defense: “I am not +a scientific engineer, but a practical one ... I know +nothing of mathematics; in my experience I have +grasped such matters as a whole; I believe that the +study of mathematics in that kind of work [tunneling] +has a tendency to dwarf the mind rather than enlighten +it....” An extreme attitude perhaps, and +one which by no means adds to Haskin’s stature, but +a not unusual one in tunnel work at the time. It +would not of course be fair to imply that such men +as Herman Haupt, Brunel the elder, and Greathead +were not accomplished theoretical engineers. But it +was their innate ability to evaluate and control the +overlying physical conditions of the site and work that +made possible their significant contributions to the +development of tunnel engineering.</p> + +<p>Tunneling remained largely independent of the +realm of mathematical analysis long after the time +when all but the most insignificant engineering works +were designed by that means. Thus, as structural +engineering has advanced as the result of a flow of +new theoretical concepts, new, improved, and strengthened +materials, and new methods of fastening, the +progress of tunnel engineering has been due more to +the continual refinement of constructional techniques.</p> + +<p class="caption3">A NEW HALL OF CIVIL ENGINEERING</p> + +<p>In the Museum of History and Technology has +recently been established a Hall of Civil Engineering +<span class="pagenum"><a name="Page_205" id="Page_205">[205]</a></span> +in which the engineering of tunnels is comprehensively +treated from the historical standpoint—something +not previously done in an American museum. +The guiding precept of the exhibit has not been to +outline exhaustively the entire history of tunneling, +but rather to show the fundamental advances which +have occurred between primitive man’s first systematic +use of fire for excavating rock in mining, and the use +in combination of compressed air, iron lining, and a +movable shield in a subaqueous tunnel at the end of +the 19th century. This termination date was selected +because it was during the period from about 1830 to +1900 that the most concentrated development took +place, and during which tunneling became a firmly +established and important branch of civil engineering +and indeed, of modern civilization. The techniques +of present-day tunneling are so fully related in current +writing that it was deemed far more useful to +devote the exhibit entirely to a segment of the field’s +history which is less commonly treated.</p> + +<div class="fig_center" style="width: 534px;"> +<a name="Fig_41_3" id="Fig_41_3"></a> +<a href="images/fig_41_3_lrg.png"> +<img src="images/fig_41_3.png" width="534" height="139" alt="" /></a> +<p class="fig_caption">Figure 3.—<span class="smcap">Hoosac Tunnel. Working of later stages</span> +with Burleigh pneumatic drills mounted on carriages. The bottom heading +is being drilled in preparation for blasting out with nitroglycerine. +MHT model—½" scale. (Smithsonian photo 49260-M.)</p> +</div> + +<p>The major advances, which have already been +spoken of as being ones of technique rather than +theory, devolve quite naturally into two basic classifications: +the one of supporting a mass of loose, +unstable, pressure-exerting material—soft-ground tunneling; +and the diametrically opposite problem of +separating rock from the basic mass when it is so +firm and solid that it can support its own overbearing +weight as an opening is forced through it—rock, or +hard-ground tunneling.</p> + +<p>To exhibit the sequence in a thorough manner, +inviting and capable of easy and correct interpretation +by the nonprofessional viewer, models offered +the only logical means of presentation. Six tunnels +were selected, all driven in the 19th century. Each +represents either a fundamental, new concept of +tunneling technique, or an important, early application +of one. Models of these works form the basis of +the exhibit. No effort was made to restrict the work +to projects on American soil. This would, in fact, have +been quite impossible if an accurate picture of tunnel +technology was to be drawn; for as in virtually all +other areas of technology, the overall development in +this field has been international. The art of mining +was first developed highly in the Middle Ages in the +Germanic states; the tunnel shield was invented by +a Frenchman residing in England, and the use of +compressed air to exclude the water from subaqueous +tunnels was first introduced on a major work by an +American. In addition, the two main subdivisions, +rock and soft-ground tunneling, are each introduced +by a model not of an actual working, but of one +typifying early classical methods which were in use +for centuries until the comparatively recent development +of more efficient systems of earth support and +rock breaking. Particular attention is given to accuracy +of detail throughout the series of eight models; +original sources of descriptive and graphic information +were used in their construction wherever possible. In +all cases except the introductory model in the rock-tunneling +series, representing copper mining by early +civilizations, these sources were contemporary +accounts.</p> + +<p>The plan to use a uniform scale of reduction +throughout, in order to facilitate the viewers’ interpretation, +unfortunately proved impractical, due to +the great difference in the amount of area to be +encompassed in different models, and the necessity +that the cases holding them be of uniform height. The +related models of the Broadway and Tower Subways +represent short sections of tunnels only 8 feet or so in +diameter enabling a relatively large scale, 1½ inches +to the foot, to be used. Conversely, in order that the +model of Brunel’s Thames Tunnel be most effective, +<span class="pagenum"><a name="Page_206" id="Page_206">[206]</a></span> +it was necessary to include one of the vertical terminal +shafts used in its construction. These were about 60 +feet in depth, and thus the much smaller scale of +¼ inch to the foot was used. This variation is not +as confusing as might be thought, for the human +figures in each model provide an immediate and +positive sense of proportion and scale.</p> + +<p>Careful thought was devoted to the internal lighting +of the models, as this was one of the critical factors in +establishing, so far as is possible in a model, an +atmosphere convincingly representative of work +conducted solely by artificial light. Remarkable +realism was achieved by use of plastic rods to conduct +light to the tiny sources of tunnel illumination, such +as the candles on the miners’ hats in the Hoosac +Tunnel, and the gas lights in the Thames Tunnel. +No overscaled miniature bulbs, generally applied in +such cases, were used. At several points where the +general lighting within the tunnel proper has been +kept at a low level to simulate the natural atmosphere +of the work, hidden lamps can be operated by push-button +in order to bring out detail which otherwise +would be unseen.</p> + +<p>The remainder of the material in the Museum’s +tunneling section further extends the two major aspects +of tunneling. Space limitations did not permit +treatment of the many interesting ancillary matters +vital to tunnel engineering, such as the unique problems +of subterranean surveying, and the extreme +accuracy required in the triangulation and subsequent +guidance of the boring in long mountain tunnels; +nor the difficult problems of ventilating long workings, +both during driving and in service; nor the several +major methods developed through the years for +driving or constructing tunnels in other than the +conventional manner.<a name="FNanchor_1_1" id="FNanchor_1_1"></a> +<a href="#Footnote_1_1" class="fnanchor">[1]</a></p> + + +<p class="caption2"><a name="Rock_Tunneling" +id="Rock_Tunneling"></a>Rock Tunneling</p> + +<p>While the art of tunneling soft ground is of relatively +recent origin, that of rock tunneling is deeply +rooted in antiquity. However, the line of its development +is not absolutely direct, but is more +logically followed through a closely related branch +of technology—mining. The development of mining +techniques is a practically unbroken one, whereas +there appears little continuity or relationship between +the few works undertaken before about the 18th +century for passage through the earth.</p> + +<p>The Egyptians were the first people in recorded +history to have driven openings, often of considerable +magnitude, through solid rock. As is true of all +major works of that nation, the capability of such +grand proportion was due solely to the inexhaustible +supply of human power and the casual evaluation of +life. The tombs and temples won from the rock +masses of the Nile Valley are monuments of perseverance +rather than technical skill. Neither the +Egyptians nor any other peoples before the Middle +Ages have left any consistent evidence that they were +able to pierce ground that would not support itself +above the opening as would firm rock. In Egypt +were established the methods of rock breaking that +were to remain classical until the first use of gun-powder +blasting in the 17th century which formed the +basis of the ensuing technology of mining.</p> + +<p>Notwithstanding the religious motives which inspired +the earliest rock excavations, more constant and +universal throughout history has been the incentive +to obtain the useful and decorative minerals hidden +beneath the earth’s surface. It was the miner who +developed the methods introduced by the early civilizations +to break rock away from the primary mass, +and who added the refinements of subterranean surveying +and ventilating, all of which were later to be +assimilated into the new art of driving tunnels of large +diameter. The connection is the more evident from +the fact that tunnelmen are still known as miners.</p> + + +<p class="caption3">COPPER MINING, B.C.</p> + +<p>Therefore, the first model of the sequence, reflecting +elemental rock-breaking techniques, depicts a hard-rock +copper mine (<a href="#Fig_41_1">fig. 1</a>). Due to the absence of +specific information about such works during the +pre-Christian eras, this model is based on no particular +period or locale, but represents in a general way, +a mine in the Rio Tinto area of Spain where copper +<span class="pagenum"><a name="Page_207" id="Page_207">[207]</a></span> +has been extracted since at least 1000 B.C. Similar +workings existed in the Tirol as early as about 1600 +B.C. Two means of breaking away the rock are +shown: to the left is the most primitive of all methods, +the hammer and chisel, which require no further +description. At the right side, the two figures are +shown utilizing the first rock-breaking method in +which a force beyond that of human muscles was +employed, the age-old “fire-setting” method. The +rock was thoroughly heated by a fierce fire built +against its face and then suddenly cooled by dashing +water against it. The thermal shock disintegrated the +rock or ore into bits easily removable by hand.</p> + +<div class="fig_center" style="width: 551px;"> +<a name="Fig_41_4" id="Fig_41_4"></a> +<a href="images/fig_41_4_lrg.png"> +<img src="images/fig_41_4.png" width="551" height="380" alt="" /></a> +<p class="fig_caption">Figure 4.—<span class="smcap">Hoosac Tunnel.</span> Bottom of the +central shaft showing elevator car and rock +skip; pumps at far right. In the center, the +top bench is being drilled by a single column-mounted +Burleigh drill. MHT model—½" +scale. (Smithsonian photo 49260-N.)</p> +</div> + +<p>The practice of this method below ground, of +course, produced a fearfully vitiated atmosphere. It +is difficult to imagine whether the smoke, the steam, +or the toxic fumes from the roasting ore was the more +distressing to the miners. Even when performed by +labor considered more or less expendable, the method +could be employed only where there was ventilation +of some sort: natural chimneys and convection currents +were the chief sources of air circulation. Despite +the drawbacks of the fire system, its simplicity and +efficacy weighed so heavily in its favor that its history +of use is unbroken almost to the present day. Fire +setting was of greatest importance during the years of +intensive mining in Europe before the advent of +explosive blasting, but its use in many remote areas +hardly slackened until the early 20th century because +of its low cost when compared to powder. For this +same reason, it did have limited application in actual +tunnel work until about 1900.</p> + +<p>Direct handwork with pick, chisel and hammer, and +fire setting were the principal means of rock removal +for centuries. Although various wedging systems +were also in favor in some situations, their importance +was so slight that they were not shown in the +model.</p> + +<p><span class="pagenum"><a name="Page_208" id="Page_208">[208]</a></span></p> +<p class="caption3">HOOSAC TUNNEL</p> + +<p>It was possible in the model series, without neglecting +any major advancement in the art of rock +tunneling, to complete the sequence of development +with only a single additional model. Many of the +greatest works of civil engineering have been those +concerned directly with transport, and hence are the +product of the present era, beginning in the early +19th century. The development of the ancient arts of +route location, bridge construction, and tunnel +driving received a powerful stimulation after 1800 +under the impetus of the modern canal, highway, and, +especially, the railroad.</p> + +<p>The Hoosac Tunnel, driven through Hoosac +Mountain in the very northwest corner of Massachusetts +between 1851 and 1875, was the first major +tunneling work in the United States. Its importance +is due not so much to this as to its being literally +the fountainhead of modern rock-tunneling technology. +The remarkable thing is that the work was +begun using methods of driving almost unchanged +during centuries previous, and was completed twenty +years later by techniques which were, for the day, +almost totally mechanized. The basic pattern of +operation set at Hoosac, using pneumatic rock drills +and efficient explosives, remains practically unchanged +today.</p> + +<p>The general history of the Hoosac project is so +thoroughly recorded that the briefest outline of its +political aspects will suffice here. Hoosac Mountain +was the chief obstacle in the path of a railroad projected +between Greenfield, Massachusetts, and Troy, +New York. The line was launched by a group of +Boston merchants to provide a direct route to the +rapidly developing West, in competition with the +coastal routes via New York. The only route +economically reasonable included a tunnel of nearly +five miles through the mountain—a length absolutely +without precedent, and an immense undertaking in +view of the relatively primitive rock-working methods +then available.</p> + +<div class="fig_right" style="width: 262px;"> +<a name="Fig_41_5" id="Fig_41_5"></a> +<a href="images/fig_41_5_lrg.png"> +<img src="images/fig_41_5.png" width="273" height="439" alt="" title="" /></a> +<p class="fig_caption">Figure 5.—<span class="smcap">Burleigh rock drill</span>, improved model +of about 1870, mounted on frame for surface work. (Catalog and price list: +The Burleigh Rock Drill Company, 1876.)</p> +</div> + +<p>The bore’s great length and the desire for rapid +exploitation inspired innovation from the outset of +the work. The earliest attempts at mechanization, +although ineffectual and without influence on tunnel +engineering until many years later, are of interest. +These took the form of several experimental machines +of the “full area” type, intended to excavate the entire +face of the work in a single operation by cutting one +or more concentric grooves in the rock. The rock +remaining between the grooves was to be blasted out. +The first such machine tested succeeded in boring a +24-foot diameter opening for 10 feet before its total +failure. Several later machines proved of equal +merit.<a name="FNanchor_2_2" id="FNanchor_2_2"></a> +<a href="#Footnote_2_2" class="fnanchor">[2]</a> +It was the Baltimore and Ohio’s eminent +chief engineer, Benjamin H. Latrobe, who in his +<i>Report on the Hoosac Tunnel</i> (Baltimore, Oct. 1, 1862, +p. 125) stated that such apparatus contained in its +own structure the elements of failure, “ ... as they +require the machines to do too much and the powder +too little of the work, thus contradicting the fundamental +principles upon which all labor-saving +machinery is framed ... I could only look upon it +as a misapplication of mechanical genius.”</p> + +<p><span class="pagenum"><a name="Page_209" id="Page_209">[209]</a></span></p> +<div class="fig_left" style="width: 450px;"> +<a name="Fig_41_6" id="Fig_41_6"></a> +<img src="images/fig_41_6.png" width="450" height="406" alt="" /> +<p class="fig_caption">Figure 6.—<span class="smcap">Hoosac Tunnel.</span> Flash-powder +photograph of Burleigh drills +at the working face. (<i>Photo courtesy of +State Library, Commonwealth of Massachusetts.</i>)</p> +</div> + +<p>Latrobe stated the basic philosophy of rock-tunnel +work. No mechanical agent has ever been able to +improve upon the efficiency of explosives for the shattering +of rock. For this reason, the logical application +of machinery to tunneling was not in replacing or +altering the fundamental process itself, but in enabling +it to be conducted with greater speed by mechanically +drilling the blasting holes to receive the explosive.</p> + +<p>Actual work on the Hoosac Tunnel began at both +ends of the tunnel in about 1854, but without much +useful effect until 1858 when a contract was let to +the renowned civil engineer and railroad builder, +Herman Haupt of Philadelphia. Haupt immediately +resumed investigations of improved tunneling methods, +both full-area machines and mechanical rock +drills. At this time mechanical rock-drill technology +was in a state beyond, but not far beyond, initial +experimentation. There existed one workable American +machine, the Fowle drill, invented in 1851. It +was steam-driven, and had been used in quarry work, +although apparently not to any commercial extent. +However, it was far too large and cumbersome to +find any possible application in tunneling. Nevertheless, +it contained in its operating principle, the +seed of a practical rock drill in that the drill rod was +attached directly to and reciprocated by a double-acting +steam piston. A point of great importance +was the independence of its operation on gravity, +permitting drilling in any direction.</p> + +<p>While experimenting, Haupt drove the work onward +by the classical methods, shown in the left-hand +section of the model (<a href="#Fig_41_2">fig. 2</a>). At the far right an +advance heading or adit is being formed by pick and +hammer work; this is then deepened into a top +heading with enough height to permit hammer +drilling, actually the basic tunneling operation. A +team is shown “double jacking,” i.e., using two-handed +hammers, the steel held by a third man. +This was the most efficient of the several hand-drilling +methods. The top-heading plan was followed so +that the bulk of the rock could be removed in the +form of a bottom bench, and the majority of drilling +would be downward, obviously the most effective +direction. Blasting was with black powder and its +commercial variants. Some liberty was taken in depicting +these steps so that both operations might be +shown within the scope of the model: in practice +<span class="pagenum"><a name="Page_210" id="Page_210">[210]</a></span> +the heading was kept between 400 and 600 feet in +advance of the bench so that heading blasts would +not interfere with the bench work. The bench +carriage simply facilitated handling of the blasted +rock. It was rolled back during blasts.</p> + +<div class="fig_left" style="width: 337px;"> +<a name="Fig_41_7" id="Fig_41_7"></a> +<img src="images/fig_41_7.png" width="337" height="424" alt="" /> +<p class="fig_caption">Figure 7.—<span class="smcap">Hoosac Tunnel. Group of miners</span> +descending the west shaft with a Burleigh drill. +(<i>Photo courtesy of State Library, Commonwealth of +Massachusetts.</i>)</p> +</div> + +<p>The experiments conducted by Haupt with machine +drills produced no immediate useful results. A drill +designed by Haupt and his associate, Stuart Gwynn, +in 1858 bored hard granite at the rate of <sup>5</sup>/<sub>8</sub> inch per +minute, but was not substantial enough to bear up +in service. Haupt left the work in 1861, victim of +intense political pressures and totally unjust accusations +of corruption and mismanagement. The work +was suspended until taken over by a state commission +in 1862. Despite frightful ineptitude and very real +corruption, this period was exceedingly important +in the long history both of Hoosac Tunnel and of rock +tunneling in general.</p> + +<p>The merely routine criticism of the project had by +this time become violent due to the inordinate length +of time already elapsed and the immense cost, compared +to the small portion of work completed. This +served to generate in the commission a strong sense +of urgency to hurry the project along. Charles S. +Storrow, a competent engineer, was sent to Europe +to report on the progress of tunneling there, and in +particular on mechanization at the Mont Cenis Tunnel +then under construction between France and Italy. +Germain Sommeiller, its chief engineer, had, after +experimentation similar to Haupt’s, invented a +reasonably efficient drilling machine which had gone +into service at Mont Cenis in March 1861. It was +a distinct improvement over hand drilling, almost +doubling the drilling rate, but was complex and highly +unreliable. Two hundred drills were required to keep +16 drills at work. But the vital point in this was the +fact that Sommeiller drove his drills not with steam, +but air, compressed at the tunnel portals and piped +to the work face. It was this single factor, one of +application rather than invention, that made the +mechanical drill feasible for tunneling.</p> + +<p>All previous effort in the field of machine drilling, on +both sides of the Atlantic, had been directed toward +steam as the motive power. In deep tunnels, with +ventilation already an inherent problem, the exhaust +of a steam drill into the atmosphere was inadmissible. +Further, steam could not be piped over great distances +due to serious losses of energy from radiation of heat, +and condensation. Steam generation within the +tunnel itself was obviously out of the question. It +was the combination of a practical drill, and the +parallel invention by Sommeiller of a practical air +compressor that resulted in the first workable application +of machine rock drilling to tunneling.</p> + +<p><span class="pagenum"><a name="Page_211" id="Page_211">[211]</a></span></p> +<div class="fig_center" style="width: 480px;"> +<a name="Fig_41_8" id="Fig_41_8"></a> +<a name="Fig_41_9" id="Fig_41_9"></a> +<img src="images/fig_41_8.png" width="478" height="299" alt="" /> +<img src="images/fig_41_9.png" width="480" height="315" alt="" /> +<p class="fig_caption">Figures 8 & 9.—<span class="smcap">Hoosac Tunnel. Contemporary engravings.</span> As such large general areas could not be sufficiently +illuminated for photography, the Museum model was based primarily on +artists' versions of the work. (<i>Science Record</i>, 1872; +<i>Leslie's Weekly</i>, 1873.)</p> +</div> + +<p><span class="pagenum"><a name="Page_212" id="Page_212">[212]</a></span></p> +<p>The Sommeiller drills greatly impressed Storrow, +and his report of November 1862 strongly favored +their adoption at Hoosac. It is curious however, that +not a single one was brought to the U.S., even on +trial. Storrow does speak of Sommeiller’s intent to +keep the details of the machine to himself until it had +been further improved, with a view to its eventual +exploitation. The fact is, that although workable, the +Sommeiller drill proved to be a dead end in rock-drill +development because of its many basic deficiencies. +It did exert the indirect influence of inspiration which, +coupled with a pressing need for haste, led to renewed +trials of drilling machinery at Hoosac. Thomas +Doane, chief engineer under the state commission, +carried this program forth with intensity, seeking and +encouraging inventors, and himself working on the +problem. The pattern of the Sommeiller drill was +generally followed; that is, the drill was designed as +a separate, relatively light mechanical element, +adapted for transportation by several miners, and +attachable to a movable frame or carriage during +operation. Air was of course the presumed power. +To be effective, it was necessary that a drill automatically +feed the drill rod as the hole deepened, and +also rotate the rod automatically to maintain a round, +smooth hole. Extreme durability was essential, and +usually proved the source of a machine’s failure. +The combination of these characteristics into a +machine capable of driving the drill rod into the rock +with great force, perhaps five times per second, was a +severe test of ingenuity and materials. Doane in 1864 +had three different experimental drills in hand, as +well as various steam and water-powered compressors.</p> + +<p>Success finally came in 1865 with the invention of +a drill by Charles Burleigh, a mechanical engineer +at the well-known Putnam Machine Works of Fitchburg, +Massachusetts. The drills were first applied +in the east heading in June of 1866. Although +working well, their initial success was limited by +lack of reliability and a resulting high expense for +repairs. They were described as having “several +weakest points.” In November, these drills were +replaced by an improved Burleigh drill which was +used with total success to the end of the work. The +era of modern rock tunneling was thus launched by +Sommeiller’s insight in initially applying pneumatic +power to a machine drill, by Doane’s persistence in +searching for a thoroughly practical drill, and by +Burleigh’s mechanical talent in producing one. The +desperate need to complete the Hoosac Tunnel may +reasonably be considered the greatest single spur to +the development of a successful drill.</p> + +<p>The significance of this invention was far reaching. +Burleigh’s was the first practical mechanical rock +drill in America and, in view of its dependability, +efficiency, and simplicity when compared to the +Sommeiller drill, perhaps in the world. The Burleigh +drill achieved success almost immediately. It was +placed in production by Putnam for the Burleigh +Rock Drill Company before completion of Hoosac in +1876, and its use spread throughout the western +mining regions and other tunnel works. For a major +invention, its adoption was, in relative terms, instantaneous. +It was the prototype of all succeeding +piston-type drills, which came to be known generically +as “burleighs,” regardless of manufacture. Walter +Shanley, the Canadian contractor who ultimately +completed the Hoosac, reported in 1870, after the +drills had been in service for a sufficient time that +the techniques for their most efficient use were fully +understood and effectively applied, that the Burleigh +drills saved about half the drilling costs over hand +drilling. The per-inch cost of machine drilling +averaged 5.5 cents, all inclusive, vs. 11.2 cents for +handwork. The more important point, that of +speed, is shown by the reports of average monthly +progress of the tunnel itself, before and after use of +the air drills.</p> + +<table style="width:15em;" summary="Tunnel data"> +<tr> + <td><i>Year</i></td> + <td class="center"><i>Average monthly<br />progress in feet</i></td> +</tr> +<tr> + <td>1865</td> + <td class="tdr" style="padding-right:5em">55</td> +</tr> +<tr> + <td>1866</td> + <td class="tdr" style="padding-right:5em">48</td> +</tr> +<tr> + <td>1867</td> + <td class="tdr" style="padding-right:5em">99</td> +</tr> +<tr> + <td>1868</td> + <td class="tdr" style="padding-right:5em">— +</td> +</tr> +<tr> + <td>1869</td> + <td class="tdr" style="padding-right:5em">138</td> +</tr> +<tr> + <td>1870</td> + <td class="tdr" style="padding-right:5em">126</td> +</tr> +<tr> + <td>1871</td> + <td class="tdr" style="padding-right:5em">145</td> +</tr> +<tr> + <td>1872</td> + <td class="tdr" style="padding-right:5em">124</td> +</tr> +</table> + +<div class="fig_right" style="width: 305px;"> +<a name="Fig_41_10" id="Fig_41_10"></a> +<a href="images/fig_41_10_lrg.png"><img src="images/fig_41_10.png" width="305" height="345" alt="" /></a> +<p class="fig_caption">Figure 10.—<span class="smcap">Trinitroglycerine blast</span> at Hoosac +Tunnel. (<i>Leslie's Weekly</i>, 1873.)</p> +</div> + +<p>The right portion of the model (<a href="#Fig_41_3">fig. 3</a>) represents +the workings during the final period. The bottom +heading system was generally used after the Burleigh +drills had been introduced. Four to six drills were +<span class="pagenum"><a name="Page_213" id="Page_213">[213]</a></span> +mounted on a carriage designed by Doane. These +drove the holes for the first blast in the center of the +heading in about six hours. The full width of the +heading, the 24-foot width of the tunnel, was then +drilled and blasted out in two more stages. As in +the early section, the benches to the rear were later +removed to the full-tunnel height of about 20 feet. +This operation is shown by a single drill (<a href="#Fig_41_4">fig. 4</a>) +mounted on a screw column. Three 8-hour shifts carried +the work forward: drilling occupied half the +time and half was spent in running the carriage back, +blasting, and mucking (clearing the broken rock).</p> + +<p>The tunnel’s 1028-foot central shaft, completed +under the Shanley contract in 1870 to provide two +additional work faces as well as a ventilation shaft is +shown at the far right side of this half of the model. +Completed so near the end of the project, only 15 +percent of the tunnel was driven from the shaft.</p> + +<p>The enormous increase in rate of progress was not +due entirely to machine drilling. From the outset +of his jurisdiction, Doane undertook experiments with +explosives as well as drills, seeking an agent more +effective than black powder. In this case, the need +for speed was not the sole stimulus. As the east and +west headings advanced further and further from the +portals, the problem of ventilation grew more acute, +and it became increasingly difficult to exhaust the +toxic fumes produced by the black powder blasts.</p> + +<p>In 1866, Doane imported from Europe a sample +of trinitroglycerine, the liquid explosive newly introduced +by Nobel, known in Europe as “glonoïn oil” +and in the United States as “nitroglycerine.” It +already had acquired a fearsome reputation from its +tendency to decompose with heat and age and to +explode with or without the slightest provocation. +Nevertheless, its tremendous power and characteristic +of almost complete smokelessness led Doane to +employ the chemist George W. Mowbray, who had +blasted for Drake in the Pennsylvania oil fields, to +develop techniques for the bulk manufacture of the +new agent and for its safe employment in the tunnel.</p> + +<div class="fig_center" style="width: 407px;"> +<a name="Fig_41_11" id="Fig_41_11"></a> +<img src="images/fig_41_11.png" width="407" height="295" alt="" /> +<p class="fig_caption">Figure 11.—<span class="smcap">Hoosac Tunnel</span> survey +crew at engineering office. The highest +accuracy of the aboveground and +underground survey work was required +to insure proper vertical and horizontal +alignment and meeting of the several +separately driven sections. (<i>Photo courtesy +of State Library, Commonwealth of +Massachusetts.</i>)</p> +</div> + +<p>Mowbray established a works on the mountain and +shortly developed a completely new blasting practice +based on the explosive. Its stability was greatly increased +by maintaining absolute purity in the manufacturing +process. Freezing the liquid to reduce its +sensitivity during transport to the headings, and +extreme caution in its handling further reduced the +hazard of its use. At the heading, the liquid was +poured into cylindrical cartridges for placement in +the holes. As with the Burleigh drill, the general +adoption of nitroglycerine was immediate once its +qualities had been demonstrated. The effect on the +work was notable. Its explosive characteristics permitted +fewer blast holes over a given frontal area of +working face, and at the same time it was capable +of effectively blowing from a deeper drill hole, 42 +inches against 30 inches for black powder, so that +under ideal conditions 40 percent more tunnel length +was advanced per cycle of operations. A new fuse +and a system of electric ignition were developed which +permitted simultaneous detonation and resulted in +a degree of effectiveness impossible with the powder +train and cord fusing used with the black powder. +Over a million pounds of nitroglycerine were produced +by Mowbray between 1866 and completion of +the tunnel.</p> + +<p><span class="pagenum"><a name="Page_214" id="Page_214">[214]</a></span></p> +<div class="fig_center" style="width: 656px;"> +<a name="Fig_41_12" id="Fig_41_12"></a> +<img src="images/fig_41_12.png" width="656" height="286" alt="" title="" /> +<p class="fig_caption">Figure 12.—<span class="smcap">Works at the central shaft, Hoosac Tunnel</span>, +for hoisting, pumping and air compressing machinery, +and general repair, 1871. (<i>Photo courtesy of State Library, +Commonwealth of Massachusetts.</i>)</p> +</div> + +<p><span class="pagenum"><a name="Page_215" id="Page_215">[215]</a></span></p> +<div class="fig_center" style="width: 659px;"> +<a name="Fig_41_13" id="Fig_41_13"></a> +<img src="images/fig_41_13.png" width="659" height="418" alt="" /> +<p class="fig_caption">Figure 13.—<span class="smcap">Hoosac Tunnel. Air-compressor building</span> +on Hoosac River near North Adams. The compressors were driven partially by +waterpower, derived from the river. (<i>Photo courtesy of State Library, +Commonwealth of Massachusetts.</i>)</p> +</div> + +<div class="fig_left" style="width: 313px;"> +<a name="Fig_41_14" id="Fig_41_14"></a> +<img src="images/fig_41_14.png" width="313" height="351" alt="" title="" /> +<p class="fig_caption">Figure 14.—<span class="smcap">West portal of Hoosac Tunnel</span> before +completion, 1868, showing six rings of lining brick. +(<i>Photo courtesy of State Library, Commonwealth of Massachusetts.</i>)</p> +</div> + +<p>When the Shanleys took the work over in 1868, +following political difficulties attending operation by +the State, the period of experimentation was over. +The tunnel was being advanced by totally modern +methods, and to the present day the overall concepts +have remained fundamentally unaltered: the Burleigh +piston drill has been replaced by the lighter +hammer drill; the Doane drill carriage by the more +flexible “jumbo”;nitroglycerine by its more stable +descendant dynamite and its alternatives; and static-electric +blasting machines by more dependable +magnetoelectric. But these are all in the nature of +improvements, not innovations.</p> + +<p>Unlike the preceding model, there was good documentation +for this one. Also, the Hoosac was apparently +the first American tunnel to be well recorded +photographically. Early flashlight views exist of the +drills working at the heading (<a href="#Fig_41_6">fig. 6</a>) as well as of the +portals, the winding and pumping works at the central +shaft, and much of the machinery and associated +aspects of the project. These and copies of drawings +of much of Doane’s experimental apparatus, a rare +technological record, are preserved at the Massachusetts +State Library.</p> + + +<p class="caption2"><a name="Soft-Ground_Tunneling" id="Soft-Ground_Tunneling"></a> +Soft-Ground Tunneling</p> + +<p>So great is the difference between hard-rock and +soft-ground tunneling that they constitute two almost +separate branches of the field. In penetrating ground +lacking the firmness or cohesion to support itself above +an opening, the miner’s chief concern is not that of +removing the material, but of preventing its collapse +into his excavation. The primitive methods depending +upon brute strength and direct application of fire +and human force were suitable for assault on rock, +but lacked the artifice needed for delving into less +stable material. Roman engineers were accomplished +in spanning subterranean ways with masonry arches, +but apparently most of their work was done by cut-and-cover +methods rather than by actual mining.</p> + +<p>Not until the Middle Ages did the skill of effectively +working openings in soft ground develop, and not +until the Renaissance was this development so consistently +successful that it could be considered a +science.</p> + +<p class="caption3">RENAISSANCE MINING</p> + +<p>From the earliest periods of rock working, the quest +for minerals and metals was the primary force that +drove men underground. It was the technology of +mining, the product of slow evolution over the +centuries, that became the technology of the early +tunnel, with no significant modification except in +size of workings.</p> + +<p>Every aspect of 16th century mining is definitively +detailed in Georgius Agricola’s remarkable <i>De re +Metallica</i>, first published in Basel in 1556. During +its time of active influence, which extended for two +centuries, it served as the authoritative work on the +subject. It remains today an unparalleled early record +of an entire branch of technology. The superb +woodcuts of mine workings and tools in themselves +constitute a precise description of the techniques of +the period, and provided an ideal source of information +upon which to base the first model in the soft-ground +series.</p> + +<p><span class="pagenum"><a name="Page_216" id="Page_216">[216]</a></span></p> +<div class="fig_center" style="width: 663px;"> +<a name="Fig_41_15" id="Fig_41_15"></a> +<a href="images/fig_41_15_lrg.png"> +<img src="images/fig_41_15.png" width="663" height="478" alt="" /></a> +<p class="fig_caption">Figure 15.—<span class="smcap">Centering for placement of finished stonework</span> +at west portal, 1874. At top-right are the sheds where +the lining brick was produced. (<i>Photo courtesy of State Library, +Commonwealth of Massachusetts.</i>)</p> +</div> + +<p>The model, representing a typical European mine, +demonstrates the early use of timber frames or +“sets” to support the soft material of the walls and roof. +In areas of only moderate instability, the sets alone +were sufficient to counteract the earth pressure, and +were spaced according to the degree of support +required. In more extreme conditions, a solid lagging +of small poles or boards was set outside the +frames, as shown in the model, to provide absolute +support of the ground. Details of the framing, the +windlass, and all tools and appliances were supplied +by Agricola, with no need for interpretation or +interpolation.</p> + +<p>The basic framing pattern of sill, side posts and cap +piece, all morticed together, with lagging used where +needed, was translated unaltered into tunneling practice, +particularly in small exploratory drifts. It +remained in this application until well into the 20th +century.</p> + +<p>The pressure exerted upon tunnels of large area +was countered during construction by timbering +systems of greater elaboration, evolved from the basic +one. By the time that tunnels of section large +enough to accommodate canals and railways were +being undertaken as matter-of-course civil engineering +works, a series of nationally distinguishable +systems had emerged, each possessing characteristic +points of favor and fault. As might be suspected, the +English system of tunnel timbering, for instance, was +rarely applied on the Continent, nor were the German, +Austrian or Belgian systems normally seen in Great +Britain. All were used at one time or another in +this country, until the American system was introduced +in about 1855. While the timbering commonly +remained in place in mines, it would be followed up +by permanent masonry arching and lining in tunnel +work.</p> + +<p>Overhead in the museum Hall of Civil Engineering +<span class="pagenum"><a name="Page_217" id="Page_217">[217]</a></span> +are frames representing the English, Austrian and +American systems. Nearby, a series of small relief +models (<a href="#Fig_41_19">fig. 19</a>) is used to show the sequence of enlargement +in a soft-ground railroad tunnel of about +1855, using the Austrian system. Temporary timber +support of tunnels fell from use gradually after the +advent of shield tunneling in conjunction with cast-iron +lining. This formed a perfect support immediately +behind the shield, as well as the permanent +lining of the tunnel.</p> + +<div class="fig_right" style="width: 294px;"> +<a name="Fig_41_16" id="Fig_41_16"></a> +<a href="images/fig_41_16_co.png"> +<img src="images/fig_41_16.png" width="294" height="401" alt="" title="" /></a> +<p class="fig_caption">Figure 16.—<span class="smcap">West portal upon completion</span>, 1876. +(<i>Photo courtesy of New-York Historical Society.</i>) + Click on image for a color version of poster.</p> +</div> + +<p class="caption3">BRUNEL’S THAMES TUNNEL</p> + +<p>The interior surfaces of tunnels through ground +merely unstable are amenable to support by various +systems of timbering and arching. This becomes less +true as the fluidity of the ground increases. The +soft material which normally comprises the beds of +rivers can approach an almost liquid condition +resulting in a hydraulic head from the overbearing +water sufficient to prevent the driving of even the +most carefully worked drift, supported by simple +timbering. The basic defect of the timbering systems +used in mining and tunneling was that there was +inevitably a certain amount of the face or ceiling +unsupported just previous to setting a frame, or +placing over it the necessary section of lagging. In +mine work, runny soil could, and did, break through +such gaps, filling the working. For this reason, +there were no serious attempts made before 1825 to +drive subaqueous tunnels.</p> + +<p>In that year, work was started on a tunnel under the +Thames between the Rotherhithe and Wapping +sections of London, under guidance of the already +famous engineer Marc Isambard Brunel (1769-1849), +father of I. K. Brunel. The undertaking is of great +interest in that Brunel employed an entirely novel +apparatus of his own invention to provide continuous +and reliable support of the soft water-bearing clay +which formed the riverbed. By means of this +“shield,” Brunel was able to drive the world’s first +subaqueous tunnel.<a name="FNanchor_3_3" id="FNanchor_3_3"></a> +<a href="#Footnote_3_3" class="fnanchor">[3]</a></p> + +<p>The shield was of cast-iron, rectangular in elevation, +and was propelled forward by jackscrews. Shelves at +top, bottom, and sides supported the tunnel roof, +floor, and walls until the permanent brick lining was +placed. The working face, the critical area, was +supported by a large number of small “breasting +boards,” held against the ground by small individual +screws bearing against the shield framework. The +shield itself was formed of 12 separate frames, each +of which could be advanced independently of the +others. The height was 22 feet 3 inches: the width +37 feet 6 inches.</p> + +<p>The progress was piecemeal. In operation the +miners would remove one breasting board at a time, +excavate in front of it, and then replace it in the +advanced position—about 6 inches forward. This +was repeated with the next board above or below, and +the sequence continued until the ground for the +entire height of one of the 12 sections had been +removed. The board screws for that section were +shifted to bear on the adjacent frames, relieving the +<span class="pagenum"><a name="Page_218" id="Page_218">[218]</a></span> +frame of longitudinal pressure. It could then be +screwed forward by the amount of advance, the +screws bearing to the rear on the completed masonry. +Thus, step by step the tunnel progressed slowly, the +greatest weekly advance being 14 feet.</p> + +<div class="fig_right" style="width: 242px;"> +<a name="Fig_41_17" id="Fig_41_17"></a> +<a href="images/fig_41_17_lrg.png"> +<img src="images/fig_41_17.png" width="242" height="389" alt="" title="" /></a> +<p class="fig_caption">Figure 17.—<span class="smcap">Soft-ground tunneling.</span> The support +of walls and roof of mine shaft by simple +timbering; 16th century. MHT model—¾" scale. +(Smithsonian photo 49260-J.)</p> +</div> + +<p>In the left-hand portion of the model is the shaft +sunk to begin operations; here also is shown the bucket +hoist for removing the spoil. The V-type steam engine +powering the hoist was designed by Brunel. At the +right of the main model is an enlarged detail of the +shield, actually an improved version built in 1835.</p> + +<p>The work continued despite setbacks of every sort. +The financial ones need no recounting here. Technically, +although the shield principle proved workable, +the support afforded was not infallible. Four or five +times the river broke through the thin cover of silt +and flooded the workings, despite the utmost caution +in excavating. When this occurred, masses of clay, +sandbags, and mats were dumped over the opening +in the riverbed to seal it, and the tunnel pumped out. +I. K. Brunel acted as superintendent and nearly lost +his life on a number of occasions. After several suspensions +of work resulting from withdrawal or +exhaustion of support, one lasting seven years, the +work was completed in 1843.</p> + +<p>Despite the fact that Brunel had, for the first time, +demonstrated a practical method for tunneling in firm +and water-bearing ground, the enormous cost of the +work and the almost overwhelming problems encountered +had a discouraging effect rather than otherwise. +Not for another quarter of a century was a similar +project undertaken.</p> + +<p>The Thames Tunnel was used for foot and light +highway traffic until about 1870 when it was incorporated +into the London Underground railway +system, which it continues to serve today. The +roofed-over top sections of the two shafts may still be +seen from the river.</p> + +<p>A number of contemporary popular accounts of the +tunnel exist, but one of the most thorough and +interesting expositions on a single tunnel work of any +period is Henry Law’s <i>A Memoir of the Thames Tunnel</i>, +published in 1845-1846 by John Weale. Law, an +eminent civil engineer, covers the work in incredible +detail from its inception until the major suspension +in late 1828 when slightly more than half completed. +The most valuable aspect of his record is a series of +plates of engineering drawings of the shield and its +components, which, so far as is known, exist nowhere +else. These formed the basis of the enlarged section +of the shield, shown to the right of the model of the +tunnel itself. A vertical section through the shield +is reproduced here from Law for comparison with +the model (figs. 21 and 23).</p> + +<p><span class="pagenum"><a name="Page_219" id="Page_219">[219]</a></span></p> +<div class="fig_center" style="width: 599px;"> +<a name="Fig_41_18" id="Fig_41_18"></a> +<a href="images/fig_41_18_lrg.png"> +<img src="images/fig_41_18.png" width="599" height="654" alt="" /></a> +<p class="fig_caption">Figure 18.—<span class="smcap">Soft-ground tunneling.</span> The model of +a 16th century mine in the Museum of History and Technology was +constructed from illustrations in such works as G. E. von Löhneyss' +<i>Bericht vom Bergwerck</i>, 1690, as well as the better known ones from +<i>De re Metallica</i>.</p> +</div> + +<p><span class="pagenum"><a name="Page_220" id="Page_220">[220]</a></span></p> +<div class="fig_center" style="width: 646px;"> +<a name="Fig_41_19" id="Fig_41_19"></a> +<a href="images/fig_41_19_lrg.png"> +<img src="images/fig_41_19.png" width="646" height="429" alt="" /></a> +<p class="center fig_caption">Figure 19.—<span class="smcap">The successive stages</span> in the +enlargement of a mid-19th century railroad tunnel, using the Austrian +system of timbering.<br />MHT model.</p> +</div> + +<p><span class="pagenum"><a name="Page_221" id="Page_221">[221]</a></span></p> +<div class="fig_center" style="width: 598px;"> +<a name="Fig_41_20" id="Fig_41_20"></a> +<a href="images/fig_41_20_lrg.png"> +<img src="images/fig_41_20.png" width="598" height="321" alt="" /></a> +<p class="center fig_caption">Figure 20.—<span class="smcap">M. I. Brunel's Thames Tunnel</span>, +1825-1843, the first driven beneath a body of water.<br />MHT model—¼" +scale. (Smithsonian photo 49260-F.)</p> +</div> + +<p class="caption3">THE TOWER SUBWAY</p> + +<div class="fig_right" style="width: 277px;"> +<a name="Fig_41_21" id="Fig_41_21"></a> +<a href="images/fig_41_21_lrg.png"> +<img src="images/fig_41_21.png" width="277" height="424" alt="" title="" /></a> +<p class="fig_caption">Figure 21.—<span class="smcap">Enlarged detail</span> of Brunel's +tunneling shield, vertical section. The +first two and part of the third of the +twelve frames are shown. To the left is +the tunnel's completed brick lining and to +the right, the individual breasting boards +and screws for supporting the face. The +propelling screws are seen at top and +bottom, bearing against the lining. +Three miners worked in each frame, one +above the other. MHT model—¾" scale. +(Smithsonian photo 49260-G.)</p> +</div> + +<p>Various inventors attempted to improve upon the +Brunel shield, aware of the fundamental soundness +of the shield principle. Almost all bypassed the +rectangular sectional construction used in the Thames +Tunnel, and took as a starting point a sectional +shield of circular cross section, advanced by Brunel +in his original patent of 1818. James Henry Greathead +(1844-1896), rightfully called the father of modern +subaqueous tunneling, surmised in later years that +Brunel had chosen a rectangular configuration for +actual use, as one better adapted to the sectional +type of shield. The English civil engineer, Peter W. +Barlow, in 1864 and 1868 patented a circular shield, +of one piece, which was the basis of one used by him in +constructing a small subway of 1350 feet beneath the +Thames in 1869, the first work to follow the lead of +Brunel. Greathead, acting as Barlow’s contractor, +was the designer of the shield actually used in the +work, but it was obviously inspired by Barlow’s +patents.</p> + +<p>The reduction of the multiplicity of parts in the +Brunel shield to a single rigid unit was of immense +advantage and an advance perhaps equal to the +shield concept of tunneling itself. The Barlow-Greathead +shield was like the cap of a telescope with +a sharpened circular ring on the front to assist in +penetrating the ground. The diaphragm functioned, +as did Brunel’s breasting boards, to resist the longitudinal +earth pressure of the face, and the cylindrical +portion behind the diaphragm bore the radial pressure +of roof and walls. Here also for the first time, a +permanent lining formed of cast-iron segments was +used, a second major advancement in soft-ground +tunneling practice. Not only could the segments be +placed and bolted together far more rapidly than +masonry lining could be laid up, but unlike the +green masonry, they could immediately bear the full +force of the shield-propelling screws.</p> + +<p>Barlow, capitalizing on Brunel’s error in burrowing +so close to the riverbed, maintained an average cover +of 30 feet over the tunnel, driving through a solid +stratum of firm London clay which was virtually +impervious to water. As the result of this, combined +with the advantages of the solid shield and the +rapidly placed iron lining, the work moved forward +at a pace and with a facility in startling contrast to +that of the Thames Tunnel, although in fairness it +must be recalled that the face area was far less.</p> + +<p>The clay was found sufficiently sound that it could +be readily excavated without the support of the diaphragm, +and normally three miners worked in front +of the shield, digging out the clay and passing it +back through a doorway in the plate. This could be +closed in case of a sudden settlement or break in. +Following excavation, the shield was advanced 18 +inches into the excavated area by means of 6 screws, +and a ring of lining segments 18 inches in length +bolted to the previous ring under cover of the overlapping +rear skirt of the shield. The small annular +space left between the outside of the lining and the +clay by the thickness and clearance of the skirt—about +an inch—was filled with thin cement grout. The +tunnel was advanced 18 inches during each 8-hour +shift. The work continued around the clock, and the +900-foot river section was completed in only 14 weeks. +<a name="FNanchor_4_4" id="FNanchor_4_4"></a> +<a href="#Footnote_4_4" class="fnanchor">[4]</a> +The entire work was completed almost without +incident in just under a year, a remarkable performance +for the world’s second subaqueous tunnel.</p> + +<p><span class="pagenum" style="clear:both;"> +<a name="Page_222" id="Page_222">[222]</a></span></p> +<div class="fig_center" style="width: 594px; clear:both;"> +<a name="Fig_41_22" id="Fig_41_22"></a> +<a href="images/fig_41_22_lrg.png"> +<img src="images/fig_41_22.png" width="594" height="648" alt="" /></a> +<p class="fig_caption center">Figure 22.—<span class="smcap">Broadside published after commencement of work</span> +on the Thames Tunnel, 1827.<br />(MHT collections.) +<a href="#Transcription">Transcription</a> of the text is +presented in the Transcriber's Notes below.</p> +</div> + +<p><span class="pagenum"><a name="Page_223" id="Page_223">[223]</a></span></p> +<div class="fig_center" style="width: 477px;"> +<a name="Fig_41_23" id="Fig_41_23"></a> +<a href="images/fig_41_23_lrg.png"> +<img src="images/fig_41_23.png" width="477" height="625" alt="" /></a> +<p class="fig_caption">Figure 23.—<span class="smcap">Vertical section through Brunel's shield.</span> The long lever, x, supported the wood centering for turning +the masonry arches of the lining. (<span class="smcap">Law</span>, +<i>A Memoir of the Thames Tunnel.</i>)</p> +</div> + +<p><span class="pagenum"><a name="Page_224" id="Page_224">[224]</a></span></p> +<div class="fig_left" style="width: 283px;"> +<a name="Fig_41_24" id="Fig_41_24"></a> +<a href="images/fig_41_24_lrg.png"> +<img src="images/fig_41_24.png" width="283" height="460" alt="" /></a> +<p class="fig_caption">Figure 24.—<span class="smcap">Thames Tunnel. Section through</span> +riverbed and tunnel following one of the break-throughs +of the river. Inspection of the damage +with a diving bell. (<span class="smcap">Beamish</span>, <i>A Memoir of the +Life of Sir Marc Isambard Brunel</i>.)</p> +</div> + +<p>The Tower Subway at first operated with cylindrical +cars that nearly filled the 7-foot bore; the cars +were drawn by cables powered by small steam +engines in the shafts. This mode of power had previously +been used in passenger service only on the +Greenwich Street elevated railway in New York. +Later the cars were abandoned as unprofitable and +the tunnel turned into a footway (<a href="#Fig_41_32">fig. 32</a>). This small +tunnel, the successful driving due entirely to Greathead’s +skill, was the forerunner of the modern subaqueous +tunnel. In it, two of the three elements +essential to such work thereafter were first applied: +the one-piece movable shield of circular section, and +the segmental cast-iron lining.</p> + +<p>The documentation of this work is far thinner than +for the Thames Tunnel. The most accurate source of +technical information is a brief historical account in +Copperthwaite’s classic <i>Tunnel Shields and the Use of +Compressed Air in Subaqueous Works</i>, published in 1906. +Copperthwaite, a successful tunnel engineer, laments +the fact that he was able to turn up no drawing or +original data on this first shield of Greathead’s, but +he presents a sketch of it prepared in the Greathead +office in 1895, which is presumably a fair representation +(<a href="#Fig_41_33">fig. 33</a>). The Tower Subway model was built +on the basis of this and several woodcuts of the working +area that appeared contemporaneously in the +illustrated press. In this and the adjacent model of +Beach’s Broadway Subway, the tunnel axis has been +placed on an angle to the viewer, projecting the bore +into the case so that the complete circle of the working +face is included for a more suggestive effect. This +was possible because of the short length of the work +included.</p> + +<p>Henry S. Drinker, also a tunnel engineer and author +of the most comprehensive work on tunneling ever +published, treats rock tunneling in exhaustive detail +up to 1878. His notice of what he terms “submarine +tunneling” is extremely brief. He does, however, +draw a most interesting comparison between the first +Thames Tunnel, built by Brunel, and the second, +built by Greathead 26 years later:</p> + +<div class="tdtb"> +<table summary="Thames Tunnel Costs"> +<tr> + <td class="vtop center" style="width:45%">FIRST THAMES TUNNEL</td> + <td class="center" style="width:45%">SECOND THAMES TUNNEL<br />(TOWER SUBWAY)</td> +</tr> +<tr> + <td>Brickwork lining, 38 feet wide by 22½ feet high.</td> + <td class="vtop">Cast-iron lining of 8 feet outside diameter.</td> +</tr> +<tr> + <td class="vtop">120-ton cast-iron shield, accommodating 36 miners.</td> + <td>2½-ton, wrought-iron shield, accommodating at most 3 men.</td> +</tr> +<tr> + <td class="vtop">Workings filled by irruption of river five times.</td> + <td>“Water encountered at almost any time could have + been gathered in a stable pail.”</td> +</tr> +<tr> + <td>Eighteen years elapsed between start and finish of work.</td> + <td class="vtop">Work completed in about eleven months.</td> +</tr> +<tr> + <td>Cost: $3,000,000.</td> + <td>Cost: $100,000.</td> +</tr> +</table> +</div> + +<p><span class="pagenum"><a name="Page_225" id="Page_225">[225]</a></span></p> +<div class="fig_center" style="width: 597px;"> +<a name="Fig_41_25" id="Fig_41_25"></a> +<a href="images/fig_41_25_lrg.png"> +<img src="images/fig_41_25.png" width="597" height="613" alt="" /></a> +<p class="fig_caption">Figure 25.—<span class="smcap">Transverse section through shield</span>, +after inundation. Such disasters, as well as the inconsistency of the +riverbed's composition, seriously disturbed the alignment of the +shield's individual sections. (<span class="smcap">Law</span>, <i>A Memoir of the Thames +Tunnel</i>.)</p> +</div> + +<p><span class="pagenum"><a name="Page_226" id="Page_226">[226]</a></span></p> +<div class="fig_center" style="width: 644px;"> +<a name="Fig_41_26" id="Fig_41_26"></a> +<a href="images/fig_41_26_lrg.png"> +<img src="images/fig_41_26.png" width="644" height="332" alt="" /></a> +<p class="fig_caption">Figure 26.—<span class="smcap">Longitudinal section through Thames Tunnel</span> +after sandbagging to close a break in the riverbed. The tunnel +is filled with silt and water. (<span class="smcap">Law</span>, <i>A Memoir of the Thames +Tunnel</i>.)</p> +</div> + +<div class="fig_center" style="width: 639px;"> +<a name="Fig_41_27" id="Fig_41_27"></a> +<a href="images/fig_41_27_lrg.png"> +<img src="images/fig_41_27.png" width="639" height="443" alt="" title="" /></a> +<p class="fig_caption">Figure 27.—<span class="smcap">Interior of the Thames Tunnel</span> shortly +after completion in 1843. (<i>Photo courtesy of New York Public Library +Picture Collection.</i>)</p> +</div> + +<p><span class="pagenum"><a name="Page_227" id="Page_227">[227]</a></span></p> +<div class="fig_center" style="width: 644px;"> +<a name="Fig_41_28" id="Fig_41_28"></a> +<a href="images/fig_41_28_lrg.png"> +<img src="images/fig_41_28.png" width="644" height="372" alt="" /></a> +<p class="fig_caption">Figure 28.—<span class="smcap">Thames Tunnel</span> in use by London +Underground railway. (<i>Illustrated London News</i>, 1869?)</p> +</div> + +<div class="fig_left" style="width: 341px;"> +<a name="Fig_41_29" id="Fig_41_29"></a> +<a href="images/fig_41_29_lrg.png"> +<img src="images/fig_41_29.png" width="341" height="273" alt="" title="" /></a> +<p class="fig_caption">Figure 29.—<span class="smcap">Placing a</span> segment of cast-iron lining +in Greathead's Tower Subway, 1869. To the rear is the shield's diaphragm +or bulkhead. MHT model—1½" scale. (Smithsonian photo 49260-B.)</p> +</div> + +<p class="caption3">BEACH’S BROADWAY SUBWAY</p> + +<p>Almost simultaneously with the construction of the +Tower Subway, the first American shield tunnel was +driven by Alfred Ely Beach (1826-1896). Beach, as +editor of the <i>Scientific American</i> and inventor of, among +other things, a successful typewriter as early as 1856, +was well known and respected in technical circles. +He was not a civil engineer, but had become concerned +with New York’s pressing traffic problem +(even then) and as a solution, developed plans for a +rapid-transit subway to extend the length of Broadway. +He invented a shield as an adjunct to this system, +solely to permit driving of the tunnel without disturbing +the overlying streets.</p> + +<p>An active patent attorney as well, Beach must +certainly have known of and studied the existing +patents for tunneling shields, which were, without +exception, British. In certain aspects his shield +resembled the one patented by Barlow in 1864, but +never built. However, work on the Beach tunnel +started in 1869, so close in time to that on the Tower +<span class="pagenum"><a name="Page_228" id="Page_228">[228]</a></span> +Subway, that it is unlikely that there was any influence +from that source. Beach had himself patented +a shield, in June 1869, a two-piece, sectional design +that bore no resemblance to the one used. His +subway plan had been first introduced at the 1867 +fair of the American Institute in the form of a short +plywood tube through which a small, close-fitting +car was blown by a fan. The car carried 12 passengers. +Sensing opposition to the subway scheme +from Tammany, in 1868 Beach obtained a charter +to place a small tube beneath Broadway for transporting +mail and small packages pneumatically, a +plan he advocated independently of the passenger +subway.</p> +<div style="clear: both;"></div> + +<div class="center"> +<table summary="Tower Subway Illustrations"> +<tr> + <td colspan="2"><a name="Fig_41_30" id="Fig_41_30"></a> + <a href="images/fig_41_30_lrg.png"> + <img src="images/fig_41_30.png" width="627" height="336" alt="" /></a> + </td> +</tr> +<tr> + <td class="fig_caption">ADVANCING THE SHIELD.</td> + <td class="fig_caption">FITTING THE CASTINGS.</td> +</tr> +<tr> + <td class="fig_caption" colspan="2">Figure 30.— <span class="smcap">Contemporary illustrations</span> of Tower Subway works used + as basis of the model in the Museum of History and Technology. + (<i>Illustrated London News</i>, 1869.) + </td> +</tr> +</table> +</div> + +<div class="fig_left" style="width: 311px;"> +<a name="Fig_41_31" id="Fig_41_31"></a> +<img src="images/fig_41_31.png" width="311" height="443" alt="" title="" /> +<p class="fig_caption">Figure 31.—<span class="smcap">Excavation in front of shield</span>, +Tower Subway. This was possible because of the +stiffness of the clay encountered. MHT model—front +of model shown in <a href="#Fig_41_29">fig. 29</a>. (Smithsonian +photo 49260-A.)</p> +</div> + +<p>Under this thin pretense of legal authorization, the +sub-rosa excavation began from the basement of a +clothing store on Warren Street near Broadway. The +8-foot-diameter tunnel ran eastward a short distance, +made a 90-degree turn, and thence southward under +<span class="pagenum"><a name="Page_229" id="Page_229">[229]</a></span> +Broadway to stop a block away under the south side +of Murray Street. The total distance was about 312 +feet. Work was carried on at night in total secrecy, +the actual tunneling taking 58 nights. At the Warren +Street terminal, a waiting room was excavated and a +large Roots blower installed for propulsion of the single +passenger car. The plan was similar to that used +with the model in 1867: the cylindrical car fitted the +circular tunnel with only slight circumferential clearance. +The blower created a plenum within the waiting +room and tunnel area behind the car of about +0.25 pounds per square inch, resulting in a thrust on +the car of almost a ton, not accounting for blowby. +The car was thus blown along its course, and was +returned by reversing the blower’s suction and discharge +ducts to produce an equivalent vacuum within +the tunnel.</p> + +<div class="fig_right" style="width: 292px;"> +<a name="Fig_41_33" id="Fig_41_33"></a> +<img src="images/fig_41_33.png" width="292" height="449" alt="" title="" /> +<p class="fig_caption">Figure 33.—<span class="smcap">Vertical section</span> through the Greathead +shield used at the Tower Subway, 1869. The +first one-piece shield of circular section. +(<span class="smcap">Copperthwaite</span>, +<i>Tunnel Shields and the Use of Compressed +Air in Subaqueous Works</i>.)</p> +</div> + + +<p>The system opened in February of 1870 and remained +in operation for about a year. Beach was +ultimately subdued by the hostile influences of Boss +Tweed, and the project was completely abandoned. +Within a very few more years the first commercially +operated elevated line was built, but the subway did +not achieve legitimate status in New York until the +opening of the Interborough line in 1904. Ironically, +its route traversed Broadway for almost the length of +the island.</p> + + +<div class="fig_left" style="width: 353px;"> +<a name="Fig_41_32" id="Fig_41_32"></a> +<a href="images/fig_41_32_lrg.png"> +<img src="images/fig_41_32.png" width="353" height="351" alt="" title="" /></a> +<p class="fig_caption">Figure 32.—<span class="smcap">Interior of completed Tower Subway.</span> +(<span class="smcap">Thornbury</span>, <i>Old and New London, 1887, +vol. 1, p. 126</i>.)</p> +</div> + + +<p>The Beach shield operated with perfect success in +this brief trial, although the loose sandy soil encountered +was admittedly not a severe test of its qualities. +No diaphragm was used; instead a series of 8 horizontal +shelves with sharpened leading edges extended +across the front opening of the shield. The outstanding +feature of the machine was the substitution +for the propelling screws used by Brunel and +Greathead of 18 hydraulic rams, set around its +circumference. These were fed by a single hand-operated +pump, seen in the center of figure 34. By +this means the course of the shield’s forward movement +could be controlled with a convenience and +<span class="pagenum"><a name="Page_230" id="Page_230">[230]</a></span> +precision not attainable with screws. Vertical and +horizontal deflection was achieved by throttling the +supply of water to certain of the rams, which could +be individually controlled, causing greater pressure +on one portion of the shield than another. This +system has not changed in the ensuing time, except, +of course, in the substitution of mechanically produced +hydraulic pressure for hand.</p> + +<div class="fig_right" style="width: 400px;"> +<a name="Fig_41_34" id="Fig_41_34"></a> +<a href="images/fig_41_34_lrg.png"> +<img src="images/fig_41_34.png" width="400" height="358" alt="" title="" /></a> +<p class="fig_caption">Figure 34.—<span class="smcap">Beach's</span> Broadway Subway. +Advancing the shield by +hydraulic rams, 1869. MHT +model—1½" scale. (Smithsonian +photo 49260-E.)</p> +</div> + +<p>Unlike the driving of the Tower Subway, no excavation +was done in front of the shield. Rather, +the shield was forced by the rams into the soil for +the length of their stroke, the material which entered +being supported by the shelves. This was removed +from the shelves and hauled off. The ram plungers +then were withdrawn and a 16-inch length of the +permanent lining built up within the shelter of the +shield’s tail ring. Against this, the rams bore for the +next advance. Masonry lining was used in the +straight section; cast-iron in the curved. The juncture +is shown in the model.</p> + +<p><span class="pagenum"><a name="Page_231" id="Page_231">[231]</a></span></p> +<div class="fig_right" style="width: 354px;"> +<a name="Fig_41_36" id="Fig_41_36"></a> +<a href="images/fig_41_36_lrg.png"> +<img src="images/fig_41_36.png" width="354" height="366" alt="" title="" /></a> +<p class="fig_caption">Figure 36.—<span class="smcap">Interior</span> of Beach Subway showing iron +lining on curved section and the pneumatically powered passenger car. +View from waiting room. (<i>Scientific American</i>, March 5, 1870.)</p> +</div> + + +<div class="fig_left" style="width: 298px;"> +<a name="Fig_41_35" id="Fig_41_35"></a> +<a href="images/fig_41_35_lrg.png"> +<img src="images/fig_41_35.png" width="298" height="419" alt="" title="" /></a> +<p class="fig_caption">Figure 35.—<span class="smcap">Vertical section</span> through the Beach +shield used on the Broadway Subway, showing the +horizontal shelves (C), iron cutting ring (B), +hydraulic rams (D), hydraulic pump (F), and rear +protective skirt (H). (<i>Scientific American</i>, March 5, +1870.)</p> +</div> + + +<p>Enlarged versions of the Beach shield were used in a +few tunnels in the Midwest in the early 1870’s, but +from then until 1886 the shield method, for no clear +reason, again entered a period of disuse finding no +application on either side of the Atlantic despite its +virtually unqualified proof at the hands of Greathead +and Beach. Little precise information remains on +this work. The Beach system of pneumatic transit is +described fully in a well-illustrated booklet published +by him in January 1868, in which the American Institute +model is shown, and many projected systems +of pneumatic propulsion as well as of subterranean +and subaqueous tunneling described. Beach again +(presumably) is author of the sole contemporary account +of the Broadway Subway, which appeared in +<i>Scientific American</i> following its opening early in 1870. +Included are good views of the tunnel and car, of the +shield in operation, and, most important, a vertical +sectional view through the shield (<a href="#Fig_41_35">fig. 35</a>).</p> + +<p>It is interesting to note that optical surveys for +maintenance of the course apparently were not used. +The article illustrated and described the driving each +night of a jointed iron rod up through the tunnel +roof to the street, twenty or so feet above, for “testing +the position.”</p> + + +<p class="caption3" style="clear:both;">THE FIRST HUDSON RIVER TUNNEL</p> + +<p>Despite the ultimate success of Brunel’s Thames +Tunnel in 1843, the shield in that case afforded only +moderately reliable protection because of the fluidity +of the soil driven through, and its tendency to enter +the works through the smallest opening in the shield’s +defense. An English doctor who had made physiological +studies of the effects on workmen of the high +air pressure within diving bells is said to have recommended +to Brunel in 1828 that he introduce an +atmosphere of compressed air into the tunnel to exclude +the water and support the work face.</p> + +<p>This plan was first formally described by Sir Thomas +Cochrane (1775-1860) in a British patent of 1830. +Conscious of Brunel’s problems, he proposed a system +of shaft sinking, mining, and tunneling in water-bearing +materials by filling the excavated area with +<span class="pagenum"><a name="Page_232" id="Page_232">[232]</a></span> +air sufficiently above atmospheric pressure to prevent +the water from entering and to support the earth. In +this, and his description of air locks for passage of men +and materials between the atmosphere and the pressurized +area, Cochrane fully outlined the essential +features of pneumatic excavation as developed since.</p> + +<table summary="tunnel details"> +<tr> + <td style="width:267px; padding:15px;"><a name="Fig_41_37" id="Fig_41_37"></a> + <a href="images/fig_41_37_lrg.png"> + <img src="images/fig_41_37.png" width="267" height="377" alt="" title="" /></a> + </td> + <td style="width:250px; padding:15px;"><a name="Fig_41_38" id="Fig_41_38"></a> + <a href="images/fig_41_38_lrg.png"> + <img src="images/fig_41_38.png" width="250" height="448" alt="" title="" /></a> + </td> +</tr> +<tr> + <td class="vtop" style="padding:15px;"><p class="fig_caption">Figure 37.— <span class="smcap">The giant Roots lobe-type blower</span> + used for propelling the car.</p> + </td> + <td style="padding:15px;"><p class="fig_caption">Figure 38.— <span class="smcap">Testing alignment</span> of the Broadway + Subway at night by driving a jointed rod up to + street level. (<i>Scientific American</i>, March 5, 1870.)</p> + </td> +</tr> +</table> + +<p style="clear:both;">In 1839, a French engineer first used the system in +sinking a mine shaft through a watery stratum. From +then on, the sinking of shafts, and somewhat later the +construction of bridge pier foundations, by the pneumatic +method became almost commonplace engineering +practice in Europe and America. Not until 1879 +however, was the system tried in tunneling work, and +then, as with the shield ten years earlier, almost +simultaneously here and abroad. The first application +was in a small river tunnel in Antwerp, only +5 feet in height. This project was successfully completed +relying on compressed air alone to support the +earth, no shield being used. The importance of the +work cannot be considered great due to its lack of +scope.</p> + +<p>In 1871 Dewitt C. Haskin (1822-1900), a west +coast mine and railroad builder, became interested +in the pneumatic caissons then being used to found +the river piers of Eads’ Mississippi River bridge at +St. Louis. In apparent total ignorance of the Cochrane +patent, he evolved a similar system for tunneling +water-bearing media, and in 1873 proposed construction +of a tunnel through the silt beneath the Hudson +to provide rail connection between New Jersey and +New York City.</p> + +<p><span class="pagenum"><a name="Page_233" id="Page_233">[233]</a></span></p> +<div class="fig_center" style="width: 631px;"> +<a name="Fig_41_39" id="Fig_41_39"></a> +<a href="images/fig_41_39_lrg.png"> +<img src="images/fig_41_39.png" width="631" height="291" alt="" /></a> +<p class="fig_caption">Figure 39.—<span class="smcap">Haskin's</span> pneumatically driven tunnel +under the Hudson River, 1880. In the engine room at top left was the +machinery for hoisting, generating electricity for lighting, and air +compressing. The air lock is seen in the wall of the brick shaft. +MHT model—0.3" scale. (Smithsonian photo 49260.)</p> +</div> + +<div class="fig_center" style="width: 626px;"> +<a name="Fig_41_40" id="Fig_41_40"></a> +<img src="images/fig_41_40.png" width="626" height="470" alt="" /> +<p class="fig_caption">Figure 40.—<span class="smcap">Artist's conception of miners</span> escaping +into the air lock during the blowout in Haskin's tunnel.</p> +</div> + +<p><span class="pagenum"><a name="Page_234" id="Page_234">[234]</a></span></p> +<p>It would be difficult to imagine a site more in need +of such communication. All lines from the south +terminated along the west shore of the river and the +immense traffic—cars, freight and passengers—was +carried across to Manhattan Island by ferry and +barge with staggering inconvenience and at enormous +cost. A bridge would have been, and still is, almost +out of the question due not only to the width of the +crossing, but to the flatness of both banks. To provide +sufficient navigational clearance (without a drawspan), +impracticably long approaches would have +been necessary to obtain a permissibly gentle grade.</p> + +<p><a name="Haskin" id="Haskin"></a> +Haskin formed a tunneling company and began +work with the sinking of a shaft in Hoboken on the +New Jersey side. In a month it was halted because +of an injunction by, curiously, the D L & W Railroad, +who feared for their vast investment in terminal and +marine facilities. Not until November of 1879 was +the injunction lifted and work again commenced. +The shaft was completed and an air lock located in +one wall from which the tunnel proper was to be +carried forward. It was Haskin’s plan to use no +shield, relying solely on the pressure of compressed +air to maintain the work faces and prevent the entry +of water. The air was admitted in late December, +and the first large-scale pneumatic tunneling operation +launched. A single 26-foot, double-track bore +was at first undertaken, but a work face of such +diameter proved unmanageable and two oval tubes +18 feet high by 16 feet wide were substituted, each +to carry a single track. Work went forward with +reasonable facility, considering the lack of precedent. +A temporary entrance was formed of sheet-iron rings +from the air lock down to the tunnel grade, at which +point the permanent work of the north tube was +started. Immediately behind the excavation at the +face, a lining of thin wrought-iron plates was built up, +to provide form for the 2-foot, permanent brick lining +that followed. The three stages are shown in the +model in about their proper relationship of progress. +The work is shown passing beneath an old timber-crib +bulkhead, used for stabilizing the shoreline.</p> + +<p>The silt of the riverbed was about the consistency of +putty and under good conditions formed a secure +barrier between the excavation and the river above. +It was easily excavated, and for removal was mixed +with water and blown out through a pipe into the +shaft by the higher pressure in the tunnel. About +half was left in the bore for removal later. The basic +scheme was workable, but in operation an extreme +precision was required in regulating the air pressure +in the work area.<a name="FNanchor_5_5" id="FNanchor_5_5"></a> +<a href="#Footnote_5_5" class="fnanchor">[5]</a> It was soon found that there +existed an 11-psi difference between the pressure of +water on the top and the bottom of the working face, +due to the 22-foot height of the unlined opening. +Thus, it was impossible to maintain perfect pneumatic +balance of the external pressure over the entire face. +It was necessary to strike an average with the result +that some water entered at the bottom of the face +where the water pressure was greatest, and some air +leaked out at the top where the water pressure was +below the air pressure. Constant attention was essential: +several men did nothing but watch the behavior +of the leaks and adjusted the pressure as the +ground density changed with advance. Air was supplied +by several steam-driven compressors at the +surface.</p> + +<p>The air lock permitted passage back and forth of men +and supplies between the atmosphere and the work +area, without disturbing the pressure differential. +This principle is demonstrated by an animated model +set into the main model, to the left of the shaft +(<a href="#Fig_41_39">fig. 39</a>). The variation of +pressure within the lock chamber +to match the atmosphere or the pressurized area, +depending on the direction of passage, is clearly +shown by simplified valves and gauges, and by the +use of light in varying color density. In the Haskin +tunnel, 5 to 10 minutes were taken to pass the miners +through the lock so as to avoid too abrupt a physiological +change.</p> + +<p><span class="pagenum"><a name="Page_235" id="Page_235">[235]</a></span></p> +<p>Despite caution, a blowout occurred in July 1880 +due to air leakage not at the face, but around the +temporary entrance. One door of the air lock jammed +and twenty men drowned, resulting in an inquiry +which brought forth much of the distrust with which +Haskin was regarded by the engineering profession. +His ability and qualifications were subjected to the +bitterest attack in and by the technical press. There +is some indication that, although the project began +with a staff of competent engineers, they were +alienated by Haskin in the course of work and at least +one withdrew. Haskin’s remarks in his own defense +indicate that some of the denunciation was undoubtedly +justified. And yet, despite this reaction, the +fundamental merit of the pneumatic tunneling method +had been demonstrated by Haskin and was immediately +recognized and freely acknowledged. It was +apparent at the same time, however, that air by itself +did not provide a sufficiently reliable support for +large-area tunnel works in unstable ground, and this +remains the only major subaqueous tunnel work +driven with air alone.</p> + +<div class="fig_center" style="width: 626px;"> +<a name="Fig_41_41" id="Fig_41_41"></a> +<img src="images/fig_41_41.png" width="626" height="611" alt="" /> +<p class="fig_caption">Figure 41.—<span class="smcap">Location of Hudson River Tunnel.</span> +(<i>Leslie's Weekly</i>, 1879.)</p> +</div> + +<p>After the accident, work continued under Haskin +until 1882 when funds ran out. About 1600 feet of +the north tube and 600 feet of the south tube had been +completed. Greathead resumed operations with a +shield for a British company in 1889, but exhaustion +of funds again caused stoppage in 1891. The tunnel +<span class="pagenum"><a name="Page_236" id="Page_236">[236]</a></span> +was finally completed in 1904, and is now in use as part +of the Hudson and Manhattan rapid-transit system, +never providing the sought-after rail link. A splendid +document of the Haskin portion of the work is S. D. V. +Burr’s <i>Tunneling Under the Hudson River</i> published in +1885. It is based entirely upon firsthand material and +contains drawings of most of the work, including the +auxiliary apparatus. It is interesting to note that +electric illumination (arc, not incandescent, lights) and +telephones were used, unquestionably the first employment +of either in tunnel work.</p> + +<div class="fig_center" style="width: 630px;"> +<a name="Fig_41_42" id="Fig_41_42"></a> +<a href="images/fig_41_42_lrg.png"> +<img src="images/fig_41_42.png" width="630" height="372" alt="" /></a> +<p class="fig_caption">Figure 42.—<span class="smcap">St. Clair Tunnel.</span> View of front of +shield showing method of excavation in firm strata. Incandescent electric +illumination was used. 1889-90. MHT model—1" scale. (Smithsonian photo +49260-D.)</p> +</div> + + +<p class="caption3">THE ST. CLAIR TUNNEL</p> + +<p>The final model of the soft-ground series reflects, as +did the Hoosac Tunnel model for hard-rock tunneling, +final emergence into the modern period. Although +the St. Clair Tunnel was completed over 70 years ago, +it typifies in its method of construction, the basic +procedures of subaqueous work in the present day. +The Thames Tunnel of Brunel, and Haskin’s efforts +beneath the Hudson, had clearly shown that by +themselves, both the shield and pneumatic systems of +driving through fluid ground were defective in practice +for tunnels of large area. Note that the earliest +successful works by each method had been of very +small area, so that the influence of adverse conditions +was greatly diminished.</p> + +<p>The first man to perceive and seize upon the benefits +to be gained by combining the two systems was, +most fittingly, Greathead. Although he had projected +the technique earlier, in driving the underground City +and South London Railway in 1886, he brought +together for the first time the three fundamental elements +essential for the practical tunneling of soft, +water-bearing ground: compressed-air support of the +work during construction, the movable shield, and cast-iron, +permanent lining. The marriage was a happy +one indeed; the limitations of each system were almost +perfectly overcome by the qualities of the others.</p> + +<p>The conditions prevailing in 1882 at the Sarnia, +Ontario, terminal of the Grand Trunk Railway, both +operational and physical, were almost precisely the +same as those which inspired the undertaking of the +<span class="pagenum"><a name="Page_237" id="Page_237">[237]</a></span> +Hudson River Tunnel. The heavy traffic at this +vital U.S.—Canada rail interchange was ferried inconveniently +across the wide St. Clair River, and the +bank and river conditions precluded construction of a +bridge. A tunnel was projected by the railway in +that year, the time when Haskin’s tribulations were +at their height. Perhaps because of this lack of precedent +for a work of such size, nothing was done +immediately. In 1884 the railway organized a tunnel +company; in 1886 test borings were made in the riverbed +and small exploratory drifts were started across +from both banks by normal methods of mine timbering. +The natural gas, quicksand, and water +encountered soon stopped the work.</p> + +<div class="fig_center" style="width: 642px;"> +<a name="Fig_41_43" id="Fig_41_43"></a> +<a href="images/fig_41_43_lrg.png"> +<img src="images/fig_41_43.png" width="642" height="359" alt="" /></a> +<p class="fig_caption">Figure 43.—<span class="smcap">Rear view of St. Clair shield</span> showing +the erector arm placing a cast-iron lining segment. The three motions of +the arm—axial, radial, and rotational, were manually powered. +(Smithsonian photo 49260-C.)</p> +</div> + +<p>It was at this time that the railway’s president +visited Greathead’s City and South London workings. +The obvious answer to the St. Clair problem lay in +the successful conduct of this subway. Joseph +Hobson, chief engineer of the Grand Trunk and of +the tunnel project, in designing a shield, is said to +have searched for drawings of the shields used in +the Broadway and Tower Subways of 1868-9, but +unable to locate any, he relied to a limited extent +on the small drawings of those in Drinker’s volume. +There is no explanation as to why he did not have +drawings of the City and South London shield at that +moment in use, unless one considers the rather unlikely +possibility that Greathead maintained its +design in secrecy.</p> + +<div class="fig_center" style="width: 606px;"> +<a name="Fig_41_44" id="Fig_41_44"></a> +<a href="images/fig_41_44_lrg.png"> +<img src="images/fig_41_44.png" width="606" height="460" alt="" /></a> +<p class="fig_caption">Figure 44.—<span class="smcap">Opening of the St. Clair Tunnel, 1891.</span> +(<i>Photo courtesy of Detroit Library, Burton Historical Collection.</i>)</p> +</div> + +<p>The Hobson shield followed Greathead’s as closely +as any other, in having a diaphragm with closable +doors, but a modification of Beach’s sharpened +horizontal shelves was also used. However, these +functioned more as working platforms than supports +for the earth. The machine was 21½ feet in diameter, +an unprecedented size and almost twice that of +Greathead’s current one. It was driven by 24 +hydraulic rams. Throughout the entire preliminary +consideration of the project there was a marked sense +of caution that amounted to what seems an almost +total lack of confidence in success. Commencement +of the work from vertical shafts was planned so that +if the tunnel itself failed, no expenditure would have +been made for approach work. In April 1888, the +<span class="pagenum"><a name="Page_238" id="Page_238">[238]</a></span> +shafts were started near both riverbanks, but before +reaching proper depth the almost fluid clay and silt +flowed up faster than it could be excavated and this +plan was abandoned. After this second inauspicious +start, long open approach cuts were made and the +work finally began. The portals were established in +the cuts, several thousand feet back from each bank +and there the tunneling itself began. The portions +under the shore were driven without air. When the +banks were reached, brick bulkheads containing air +locks were built across the opening and the section +beneath the river, about 3,710 feet long, driven under +air pressure of 10 to 28 pounds above atmosphere. +For most of the way, the clay was firm and there was +little air leakage. It was found that horses could not +survive in the compressed air, and so mules were +used under the river.</p> + +<p>In the firm clay, excavation was carried on several +feet in front of the shield, as shown in the model +(<a href="#Fig_41_42">fig. 42</a>). About twelve +miners worked at the face. However, +in certain strata the clay encountered was so +fluid that the shield could be simply driven forward by +the rams, causing the muck to flow in at the door +openings without excavation. After each advance, +the rams were retracted and a ring of iron lining +segments built up, as in the Tower Subway. Here, +for the first time, an “erector arm” was used for +placing the segments, which weighed about half a ton. +In all respects, the work advanced with wonderful +facility and lack of operational difficulty. Considering +<span class="pagenum"><a name="Page_239" id="Page_239">[239]</a></span> +the large area, no subaqueous tunnel had ever +been driven with such speed. The average monthly +progress for the American and Canadian headings +totaled 455 feet, and at top efficiency 10 rings or a +length of 15.3 feet could be set in a 24-hour day in +each heading. The 6,000 feet of tunnel was driven in +just a year; the two shields met vis-a-vis in August of +1890.</p> + +<p>The transition was complete. The work had been +closely followed by the technical journals and the +reports of its successful accomplishment thus were +brought to the attention of the entire civil engineering +profession. As the first major subaqueous tunnel +completed in America and the first in the world of +a size able to accommodate full-scale rail traffic, the +St. Clair Tunnel served to dispel the doubts surrounding +such work, and established the pattern for a mode +of tunneling which has since changed only in matters +of detail.</p> + +<p>Of the eight models, only this one was built under +the positive guidance of original documents. In the +possession of the Canadian National Railways are +drawings not only of all elements of the shield and +lining, but of much of the auxiliary apparatus used +in construction. Such materials rarely survive, and +do so in this case only because of the foresight of the +railway which, to avoid paying a high profit margin +to a private contractor as compensation for the risk +and uncertainty involved, carried the contract itself +and, therefore, preserved all original drawing records.</p> + +<p>While the engineering of tunnels has been comprehensively +treated in this paper from the historical +standpoint, it is well to still reflect that the advances +made in tunneling have not perceptibly removed the +elements of uncertainty but have only provided more +positive and effective means of countering their +forces. Still to be faced are the surprises of hidden +streams, geologic faults, shifts of strata, unstable materials, +and areas of extreme pressure and temperature.</p> + + +<p class="caption2"><a name="BIBLIOGRAPHY" id="BIBLIOGRAPHY"></a>BIBLIOGRAPHY</p> + +<p class="references"><span class="smcap">Agricola, Georgius.</span> <i>De re Metallica.</i> [English +transl. H. C. and L. H. Hoover (<i>The Mining Magazine</i>, +London, 1912).] Basel: Froben, 1556.</p> + +<p class="references"><span class="smcap">Beach, Alfred Ely.</span> <i>The pneumatic dispatch.</i> New +York: The American News Company, 1868.</p> + +<p class="references"><span class="smcap">Beamish, Richard.</span> <i>A memoir of the life of Sir Marc +Isambard Brunel.</i> London: Longmans, Green, Longmans +and Roberts, 1862.</p> + +<p class="references"><span class="smcap">Burr, S. D. V.</span> <i>Tunneling under the Hudson River.</i> +New York: John Wiley and Sons, 1885.</p> + +<p class="references"><span class="smcap">Copperthwaite, William Charles.</span> <i>Tunnel shields +and the use of compressed air in subaqueous works.</i> New +York: D. Van Nostrand Company, 1906.</p> + +<p class="references"><span class="smcap">Drinker, Henry Sturgess.</span> <i>Tunneling, explosive compounds +and rock drills.</i> New York: John Wiley and +Sons, 1878.</p> + +<p class="references"><span class="smcap">Latrobe, Benjamin H.</span> Report on the Hoosac +Tunnel (Baltimore, October 1, 1862). Pp. 125-139, +app. 2, in <i>Report of the commissioners upon the Troy +and Greenfield Railroad and Hoosac Tunnel</i>. Boston, +1863.</p> + +<p class="references"><span class="smcap">Law, Henry.</span> A memoir of the Thames Tunnel. +<i>Weale’s Quarterly Papers on Engineering</i> (London, +1845-46), vol. 3, pp. 1-25 and vol. 5, pp. 1-86.</p> + +<p class="references">The pneumatic tunnel under Broadway, N.Y. +<i>Scientific American</i> (March 5, 1870), pp. 154-156.</p> + +<p class="references"><i>Report of the commissioners upon the Troy and Greenfield +Railroad and Hoosac Tunnel to his excellency the governor +and the honorable the executive council of the state of +Massachusetts, February 28, 1863.</i> Boston, 1863.</p> + +<p class="references"><span class="smcap">Storrow, Charles S.</span> Report on European tunnels +(Boston, November 28, 1862). Pp. 5-122, app. 1, in +<i>Report of the commissioners upon the Troy and Greenfield +Railroad and Hoosac Tunnel....</i> Boston, 1863.</p> + +<p class="references pmb4">The St. Clair Tunnel. <i>Engineering News</i> (in series +running October 4 to December 27, 1890).</p> + + +<p class="caption2"><a name="FOOTNOTES" id="FOOTNOTES"></a>FOOTNOTES:</p> + +<div class="footnote"><p><a name="Footnote_1_1" id="Footnote_1_1"></a><a href="#FNanchor_1_1"><span class="label">[1]</span></a> There are two important secondary techniques for opening +subterranean and subaqueous ways, neither a method truly of +tunneling. One of these, of ancient origin, used mainly in the +construction of shallow subways and utility ways, is the “cut +and cover” system, whereby an open trench is excavated and +then roofed over. The result is, in effect, a tunnel. The concept +of the other method was propounded in the early 19th +century but only used practically in recent years. This is the +“trench” method, a sort of subaqueous equivalent of cut and +cover. A trench is dredged in the bed of a body of water, +into which prefabricated sections of large diameter tube are +lowered, in a continuous line. The joints are then sealed by +divers, the trench is backfilled over the tube, the ends are +brought up to dryland portals, the water is pumped out, and a +subterranean passage results. The Chesapeake Bay Bridge +Tunnel (1960-1964) is a recent major work of this character.</p></div> + +<div class="footnote"><p><a name="Footnote_2_2" id="Footnote_2_2"></a><a href="#FNanchor_2_2"><span class="label">[2]</span></a> In 1952 a successful machine was developed on this plan, +with hardened rollers on a revolving cutting head for disintegrating +the rock. The idea is basically sound, possessing advantages +in certain situations over conventional drilling and +blasting systems.</p></div> + +<div class="footnote"><p><a name="Footnote_3_3" id="Footnote_3_3"></a><a href="#FNanchor_3_3"><span class="label">[3]</span></a> In 1807 the noted Cornish engineer Trevithick commenced +a small timbered drift beneath the Thames, 5 feet by 3 feet, as +an exploratory passage for a larger vehicular tunnel. Due to +the small frontal area, he was able to successfully probe about +1000 feet, but the river then broke in and halted the work. +Mine tunnels had also reached beneath the Irish Sea and various +rivers in the coal regions of Newcastle, but these were so far +below the surface as to be in perfectly solid ground and can +hardly be considered subaqueous workings.</p></div> + +<div class="footnote"><p><a name="Footnote_4_4" id="Footnote_4_4"></a><a href="#FNanchor_4_4"><span class="label">[4]</span></a> Unlike the Brunel tunnel, this was driven from both ends +simultaneously, the total overall progress thus being 3 feet per +shift rather than 18 inches. A top speed of 9 feet per day could +be advanced by each shield under ideal conditions.</p></div> + +<div class="footnote"><p><a name="Footnote_5_5" id="Footnote_5_5"></a><a href="#FNanchor_5_5"><span class="label">[5]</span></a> Ideally, the pressure of air within the work area of a +pneumatically driven tunnel should just balance the hydrostatic head of +the water without, which is a function of its total height above the +opening. If the air pressure is not high enough, water will, of course, +enter, and if very low, there is danger of complete collapse of the +unsupported ground areas. If too high, the air pressure will overcome +that due to the water and the air will force its way out through the +ground, through increasingly larger openings, until it all rushes out +suddenly in a “blowout.” The pressurized atmosphere gone, the water then +is able to pour in through the same opening, flooding the workings.</p></div> + + +<p class="caption2"><a name="INDEX" id="Index"></a><i>Index</i></p> + +<p style="text-indent:0"> +Agricola, Georgius, <a href="#Page_215">215</a>,<a href="#Page_216">216</a><br /> +<br /> +Barlow, Peter W., <a href="#Page_221">221</a>, <a href="#Page_227">227</a><br /> +Beach, Alfred Ely, <a href="#Page_224">224</a>, + <a href="#Page_227">227</a>-<a href="#Page_229">229</a>, + <a href="#Page_231">231</a>, <a href="#Page_237">237</a><br /> +Brunel, Marc Isambard (the elder), <a href="#Page_204">204</a>, + <a href="#Page_205">205</a>, <a href="#Page_217">217</a>, + <a href="#Page_218">218</a>, <a href="#Page_221">221</a>, + <a href="#Page_224">224</a>, <a href="#Page_229">229</a>, + <a href="#Page_231">231</a>, <a href="#Page_236">236</a><br /> +Burleigh, Charles, <a href="#Page_212">212</a>, <a href="#Page_213">213</a><br /> +Burleigh Rock Drill Company, <a href="#Page_212">212</a><br /> +Burr, S. D. V., <a href="#Page_236">236</a><br /> +<br /> +Cochrane, Sir Thomas, <a href="#Page_231">231</a>, <a href="#Page_232">232</a><br /> +Copperthwaite, William Charles, <a href="#Page_224">224</a><br /> +<br /> +Doane, Thomas, <a href="#Page_210">210</a>, <a href="#Page_212">212</a>, + <a href="#Page_213">213</a>, <a href="#Page_215">215</a><br /> +Drinker, Henry S., <a href="#Page_224">224</a>, <a href="#Page_237">237</a><br /> +<br /> +Greathead, James Henry, <a href="#Page_204">204</a>, <a href="#Page_218">218</a>, + <a href="#Page_221">221</a>, <a href="#Page_224">224</a>, + <a href="#Page_229">229</a>, <a href="#Page_231">231</a>, + <a href="#Page_235">235</a>-<a href="#Page_237">237</a><br /> +Gwynn, Stuart, <a href="#Page_210">210</a><br /> +<br /> +Haskin, DeWitt C., <a href="#Page_204">204</a>, <a href="#Page_232">232</a>, + <a href="#Page_234">234</a>-<a href="#Page_236">236</a><br /> +Haupt, Herman, <a href="#Page_204">204</a>, <a href="#Page_209">209</a>, + <a href="#Page_210">210</a><br /> +Hobson, Joseph, <a href="#Page_237">237</a><br /> +<br /> +Latrobe, Benjamin H., <a href="#Page_208">208</a>, <a href="#Page_209">209</a><br /> +Law, Henry, <a href="#Page_218">218</a><br /> +<br /> +Mowbray, George W., <a href="#Page_213">213</a>, <a href="#Page_215">215</a><br /> +<br /> +Nobel, Alfred B., <a href="#Page_213">213</a><br /> +<br /> +Putnam Machine Works, <a href="#Page_212">212</a><br /> +<br /> +Shanley, Walter, <a href="#Page_212">212</a><br /> +Shanley Bros., <a href="#Page_215">215</a><br /> +Sommeiller, Germain, <a href="#Page_210">210</a><br /> +Storrow, Charles S., <a href="#Page_210">210</a><br /> +<br /> +Tweed, William Marcy (Boss), <a href="#Page_229">229</a><br /> +<br /> +Weale, John, <a href="#Page_218">218</a><br /> +</p> + +<div class="trans_notes"> + + +<p class="caption2">Transcriber’s Notes</p> + +<p>All obvious typographical errors corrected. Formatting inconsistancies +and spelling were standardized. Paragraphs split by illustrations were +rejoined. The <a href="#INDEX">Index</a> was extracted from the full publication Index.</p> + + +<div style="width:60%; background-color:#f0f080;padding:7px; margin-left:auto; margin-right:auto;"> +<a name="Transcription" id="Transcription"></a> +<p class="center caption3 pmb2">Transcription of the text in <a href="#Fig_41_22">Figure 22</a>. The text +was transcribed with a slight modification to the figure description portion.</p> + +<p class="center"><b>OPEN TO THE PUBLIC EVERY DAY</b> <i>(Sundays excepted)<br /> +from Seven in the Morning, until Eight in the Evening</i>,</p> + +<p class="caption2">THE THAMES TUNNEL.</p> + +<p class="references">Fig. 1 shows a transverse section of the Thames, and beneath it a +longitudinal section of the Tunnel, as it will be when completed; +with the ascents in the inclinations in which they will be +finished.</p> + +<p class="references">Fig. 2 shows the two arched entrances of the Tunnel from the shaft.</p> + +<p class="references">Fig. 3 is a representation of the iron shield, and shows a workman +in each of the compartments.</p> + +<p>The Entrance to the Tunnel is near to Rotherhithe Church, and nearly +opposite to the London-Docks. The nearest landing place from the river +is Church Stairs. The Greenwich and Deptford coaches which go the lower +road, start hourly from Charing-cross, and Gracechurch-street, and pass +close by the works at Rotherhithe.</p> + +<p>Books relative to the Tunnel may be had at the works.</p> + +<p>The Public may view the Tunnel every day (Sundays excepted) from Seven +in the morning until Eight in the Evening, upon payment of One Shilling +each Person.</p> + +<p>The extreme northern end of the Tunnel is for the present secured by a +strong wall; but visitors will find a dry, warm, and gravelled +promenade, as far as to almost the centre of the river, and brilliantly +lighted with oil gas.</p> + +<p>The entrance is from Rotherhithe Street, and by a safe, commodious, and +easy stair case.</p> + +<p class="center">H. Teape & Son, Printers, Tower-hill, London.</p> +</div> + +</div> + + + + + + + + +<pre> + + + + + +End of the Project Gutenberg EBook of Tunnel Engineering. A Museum Treatment, by +Robert M. 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