108 TUNNELING 



cartridge and its explosion. The liquid oxygen, with which 

 the cartridge, containing kieselguhr (silicious earth) and 

 paraffin, is saturated, evaporates very readily, losing power 

 every moment ; hence the effect of each cartridge cannot be 

 guaranteed, and though it is an exceedingly powerful explosive 

 when used immediately after manufacture, no practical result 

 has yet been obtained. 



Power Station. Water is abundant at either end, and there- 

 fore hydraulic power is the motive force employed. On the 

 Italian side, a darn 5 ft. high has been thrown across the Diveria 

 at a point near the Swiss frontier, about 3 miles above the site 

 of the installations. A portion of the water thus held back 

 enters, through regulating doors and gratings, a masonry 

 channel leading to two parallel settling tanks, each 111 ft. by 

 16 ft., whence, after dropping all its sand and solid matter, the 

 now pure water passes into the water-house, and, after flowing 

 over a dam, through a grating and past the admission doors, 

 enters a metallic conduit of 3-ft. pipes. Each of the settling 

 tanks and the approach canal are provided with doors at the 

 lower end leading direct to the river, through which all the 

 sand and solid matter deposited can be scoured naturally by 

 allowing the river-water to rush freely through. For this pur- 

 pose the floor of the basins is on an average gradient of 1 in 30. 

 For a similar reason the river-bed just outside the entrance to 

 the approach canal is lined with wooden planks, from which 

 the stones collecting behind the dam can be scoured by allow- 

 ing an iron flap, hinged at the bottom, to change its position 

 from the vertical to the horizontal in a gap left purposely in the 

 dam, so causing a rushing torrent to sweep it clean. 



The chief levels are : 



Level of water at dam 794.00 meters above sea level. 



" in water-house 703.70 " " " " 



" at turbines 618.50 " " " " 



giving a total fall of 175.20 ms. or 570 ft., and a pressure of 

 17.52 atmospheres. 



