432 Mr. Francis Fox [May 25, 



between the arch of the tunnel, and the gauge of maximum 

 construction (see Fig. 6). The results are remarkable ; the volumes 

 of air thrown into the tunnel per minute being as follows : — 



cub. ft. 



Direct from the fan 161,860 



Induced draught through open tunnel mouth 48,140 



Total 210,000 



Or 100 cubic metres per second. 



The temperature of the tunnel air before the fan was started was 

 107° F., with 97 per cent, of moisture, whereas, after the fan had been 

 running a few minutes the temperature was 81° F., or a lowering of 

 26° F.j and the tunnel was cool and free from smoke and vapour. 



One can travel through with both windows open and feel no in- 

 convenience, the only remark of the brakesman riding on the top of 

 the wagons and carriages being that he finds it almost too cold. 



This application is without doubt the solution of the difficult 

 problem of tunnel ventilation under high mountains, and elsewhere 

 where shafts are not available, and where electric traction is not 

 applicable. 



This system has within the last twelve months been brought into 

 operation on the St. Gothard, with the most satisfactory results. 

 Careful experiments are being made, but there is no doubt that the 

 problem has been solved. 



In addition to these tunnels, the Saccardo system has been 

 applied to the Giovi Tunnel near Genoa — 3300 metres in length — 

 and is being installed on the Giovi Tunnel on the Genoa-Eonco 

 Railway, 8303 metres in length, besides on some seven other tunnels 

 in Italy ; and plans are being prepared for the Mont Cenis. 



The Simplon Tunnel. 



This tunnel is now in rapid course of construction, the total length 

 of gallery driven up to end of April being as follows : — 



yards. 



On the north or Brigue side of the Alps 3228 



On the south or Iselle „ „ 2350 



Or oyer three miles in little more than 18 months, including the 

 necessarily slow progress at the commencement. 



The total distance between the two portals will be 21,564 yards, 

 or 12-26 miles. A gallery of direction has been driven at both 

 ends until the actual tunnels are reached, so as to form a directly 

 straight line for the accurate alignment of the work, from end to end. 



This great undertaking will consist of two single-line tunnels 

 running parallel one to the other, at a distance apart from centre 



