148 THE POPULAR SCIENCE MONTHLY. 



rock, so that blasting was necessary. The use of explosives vitiated 

 the air, Avhile the lengtli of the passage and the impossibility of sink- 

 ing shafts made the ventilation question a vital one. Had the drills 

 been run by steam, the presence of steam-engines constantly generat- 

 ing smoke and gas would have heated and vitiated the air still further. 

 By the new invention the difficulty was met. The air was compressed 

 outside the tunnel, and conveyed into it by pipes. Here a double pur- 

 pose was served : by its expansion and liberation the air ran the drills, 

 and ventilated the tunnel. The invention which makes this practicable 

 is called the Sommeiller machine, from the name of the chief inventor. 



In an address delivered before the American Geographical Society 

 in December, 1879, Major S. F. Shelbourne referred to the manner in 

 which the work in the Alpine tunnels was accelerated by inventions. 

 The subject of the address was the San Bias route for an interoceanic 

 canal. To construct a canal at this point, it would be necessary to 

 cut a ship-tunuel seven miles long ; and it was the purpose of Major 

 Shelbourne to show that the advances made in the mechanical arts 

 during the building of the Alpine tunnels, made a ship-tunnel much 

 more practicable than Avas supposed. It may be added that, at the 

 time referred to (1879), three competent American authorities — Major 

 Shelbourne, Walton W. Evans, and Frederick M. Kelley — advocated 

 the San Bias route. Of all the routes proposed, it was the shortest, 

 the distance being thirty-three miles from sea to sea, against forty- 

 six at Panama. After the work had been begun at Panama, how- 

 ever, Mr. Kelley, whose interest in the subject was so great that he 

 spent out of his private fortune $120,000 for surveys upon the Isthmus, 

 became an advocate of that undertaking. 



Major Shelbourne said : 



In 1803 tlie progress made in the Mont Cenis Tunnel with hand-drilling, and 

 powder as an explosive, was an average of a foot and a half a day. After they 

 had commenced to introduce power-drilling and the Sommeiller machine, the 

 progress they made was three times greater — that is, four and a half feet per day. 



Major Shelbourne next adduced the testimony of Mr. Shanly, the 

 contractor of the Iloosac Tunnel, after observing that in 1872 the 

 Hoosac Tunnel was " in the rush of its progress " under him. Mr. 

 Shanly stated, in 1874 : "The use of the machine-drills saved about 

 two thirds of the expense of drilling. The expense of labor would 

 have been, I think, fully three times the cost of machine-drilling." 

 Major Shelbourne next cited the progress effected at St. Gothard, the 

 contract for which was taken in 1872 by Louis Favre, of Geneva : 



In the St. Gothard Tunnel, from 1875 to 1877, with the greater perfection 

 of exjdosives — for they had come to use nitro-glycerine — and hy means of im- 

 proved drills,* tliey made a progress of five to one, that is to say, they excavated 



* An account of the drills used in the St. Gothard Tunnel may bo found in Simnis's 

 " Tunneling," pp. 305-320. 



