TUNNELS. 

 Comparative Table of some of tJie largest Tunnels. 



129 



A tunnel has been projected at Mt. Cenis, on the line of the Lyons and Turin railway, of the 

 length of 7.6 miles; the gradient in the tunnel to be 105 feet to the mile; the section of the 

 tunnel to be 19 by 25 feet; no shafts to be used. By the aid of machinery it was expected to 

 complete this work in five years, at an expense of $2,615,000. 



The inventor of the machine and the engineer of the road is the Chevalier Mause. His plans 

 and estimates were submitted to, and approved by, a board of eminent engineers and geologists, 

 among whom was the celebrated Mr. Robert Stevenson. 



The tunnel projected through the Hoesack mountain was to have been 4 miles long, 23 feet 

 by 22 feet ; two shafts about 850 feet and 750 feet deep, 10 feet in diameter. The cost variously 

 estimated at from $2,000,000 to $3,000,000. Time estimated by different engineers at from 

 four to ten years. The machinery designed for boring did not succeed, and the project has not 

 as yet been commenced seriously. 



At the crossing of the Blue Ridge by the Virginia Central railroad there are four tunnels. The 

 main tunnel is 4,280 feet in length ; has been four years under construction, and is estimated to 

 require two years more to complete it. No shafts are used. It is ventilated by machinery. 

 A portion of it is lined. It is for a single track, and is in the clear 21 feet high by 15 feet in width. 

 Where lined, the abutments of the lining are 4 feet thick ; the arches 3 feet thick. The excavation 

 in these places is 26 feet high by 23 feet wide. 



A portion of one of the small tunnels is through a very difficult formation of loose rock and 

 earth. In the main tunnel much trouble is experienced from the water. 



The main tunnel is 700 feet below the crest of the mountain through which it passes. The 



workmen are arranged in three reliefs, and work night and day. No machinery is used for boring 



or excavating. It is the opinion of the engineer that no machinery can be applied when the tunnel 



requires lining, for want of space. He states that no excavating machine has yet been successful. 



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