ing the large area, no subaqueous tunnel had ever 

 been driven with such speed. The average monthly 

 progress for the American and I .im.hIi.ih headings 

 totaled 455 feet, and al top efficiency 1" rings or a 

 length ill 15.3 feet could be set in .i 2 Idiom da) in 

 '■i< h heading. I he 6,000 feel of tunnel was driven in 

 just .i year; the two shields met vis-a-vis in August of 

 1890. 



The transition was complete. The work had been 

 closel) followed by the technical journals and the 

 reports of its successful accomplishment thus were 

 broughl to the attention "l the entire civil engineering 

 profession. As the first major subaqueous tunnel 

 completed in Ameria and the first in the world of 



.i M/e able i date full-scale rail traffic, the 



Si < lair Tunnel served to dispel the doubts surround- 

 ing such work, and established the pattern for a mode 

 of tunneling which has since changed only in matters 



of det.nl. 



< M the eight models, only this one was buil! und< i 



the positive guidance ol original documents. In the 

 possession ol the Canadian National Railways are 

 drawings not only ol all elements ol the shield and 

 lining, but of much of the auxiliary apparatus used 

 in construction. Such materials rarel) survive, and 

 do so in tins c ase onl) be< ause ol the foresighl ol 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 draw 



While the engineering ol tunnels has been compre- 

 hensive!) treated in this papei from the historical 



standpoint, it is well in still reflet t that the ail 



made- in tunneling have not perceptibl) removed the 

 elements of uncertainly but have onl) provided more 

 positive and effective means hi countering their 

 forces. Still to be faced are the surprises ol hidden 



. lmuIu'jm faults, shifts ill strata, unstable ma- 

 terials, and areas nl extreme piessine and temperature. 



BIBLIOGRAPHY 



Vgrh i 'i \. icn s, /> n Metall . a, [English 



transl. II. C. and L. H. Hoover i The Mining Maga- 

 zine, London. l')12).| Basel: Froben, 1556. 



Beach, Alfred Ely. /•• I (patch. New 



York: The American News Company, 1868. 



Beamish, Richard. .1 memoir of the life of Sir Man 

 Isambard Brunei. London: Longmans, Green. Long- 

 mans and Roberts, 1 862. 



Burr, S. I). V. Tunneling undei tfu II 

 New York: John Wiley and Sons, 1885. 



COPPERTHWAITE, WlLLIAM CHARLES. 'runnel shields 

 and I lie use of compressed air in subaqueous works. New 

 York: I). Van Nostrand Company, 1906. 



Drinker, Henry Sturgess. Tunnel t com- 



jiounds and rock drills. .New York : John Wiley and 

 Sons, 1878. 



Latrobe, Benjamin II. Report on the Hoosac 

 I unnel (.Baltimore, October 1, 1862). Pp. 125-139, 



app. 2. in Report oj i 



and Gi Boston, 



1863. 

 Law, Henry. A memoir of the Thames Tunnel. 



H tle'i Quarterly Papers n> ng (London, 



1845 46), vol. 3, pp. 1-25 and vol. 5, pp. 1 86. 

 The pneumatic tunnel under Broadwav. N.Y. 



& ' I in (March 5. l<S~o). pp. 151 156. 



tnfield 



Railroad and Hoosac Tunnel to his excellency the governor 



and the honorable the ex incil of the state of 



Massa Boston, 1863. 



Storrow. Charles S. Report on European tunnels 



(Boston, November 28, 1862). Pp.5 122, app. 1, in 



.'.'/ Greenfield 



Railroad and Hoosac Tunnel. . . . Boston. 1863. 

 The St. (lair Tunnel. Eng i series 



running < )ctober 4 to December 27, 1890). 



PAPER 41: TUNNEL ENGINEERING A MUSEUM TREATMEN1 



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