THE GREAT ALPINE TUNNP^LS, 627 



Mont Cenis, and 1,986 feet lower than that of tlie Arll^erg-. This i.s a 

 matter of great importance in the ((ue.stion of hauhige of all the tratiic. 



The tunnel enters the mountain at the present level of the railway 

 at Brigue, so that no costly approaches are requisite on this side; but 

 on the Iselle side, the connecting line with the existing railwa}' at 

 Domo d'Ossola necessitates heavy work with one helical tunnel. The 

 gradient on the northern portion of the tunnel will only be that sutfi- 

 cient for drainage, viz, 1 in 500, but on the southern portion the 

 gradient will be 7 per 1,000, or 1 in 142. 



Admirable arrangements have been made for the welfare of the 

 men, to avoid the heavy death rate which occurred on the St. Gothard, 

 and it ma}^ be interesting to state what some of these are. For every 

 cubic foot of air sent into the latter tunnel, fifty times as much will be 

 delivered into the Simplon. Special arrangements are made for cool- 

 ing the air by means of fine jets of water and spray. 



The men on emerging from their work, wet through and fatigued, 

 are not allowed to go from the warm headings into the cold Alpine air 

 outside, but pass into a large building which is suitably warmed, and 

 where they change their mining clothes and are provided with hot 

 and cold douche baths. They put on warm dry clothes, and can 

 obtain excellent food at a moderate cost before returning to their 

 homes. Their wet and dirty mining clothes are taken charge of ])y 

 appointed custodians, who dry and clean them ready for the morrow's 

 work. These and other precautions are expected to reduce the death 

 rate to a very great extent. 



With a view to the rapid advancement of the work, the late M. 

 Brandt, whose death is greatly to be deplored, devised after his long 

 experience on the St. Gothard his now well-known drill. As details 

 of this have been published, and as they would be too technical for 

 this evening's discourse, it will only be necessary to refer to them 

 briefly. This drill is nonpercussive, nor is it armed with diamond. 

 It is a rotary drill 3 inches in diameter with a pressure on the cutting 

 points of 10 tons moving at slow speed, but capable of being acceler- 

 ated at pleasure, and of being rapidly withdrawn. It is armed with a 

 steel tool with 3 cutters, of which samples are on the table. The car- 

 riage on which it is mounted enables it to work in any direction. The 

 face of the tunnel is attacked by 10 to 12 holes in the case of the 

 hardest rock, those in the cgnter being 3 feet 3 inches in depth, while 

 those round the circumference are 4 feet 7 inches. The drills are 

 driven by hydraulic pressure of 100 atmospheres, or 1,470 pounds, to 

 the inch, and the cutter having a three-quarter-inch hole along its 

 center, all the waste water is discharged right onto the cutting edges, 

 thus keeping them cool and washing out the debris. 



The time taken for each portion of the attack in the hard Antigorio 

 gneiss is as follows: Bringing up and adjustment of drills, twenty 



