WIRE-TKAMWAYS. 



353 



of wire closely twisted round a hempen cord and extending without 

 supports from the top to the bottom of a declivity. One serves 

 for the descent of laden cars, and the other for the ascent of the 

 empty ones. The upper ends are fastened to large trees and 

 run over a pair of iron rails, which are curved downwards in front, 

 (fig. 195). The lower ends are wound round horizontal cylinders, 

 which can he turned by means of levers and cog-wheels, so as to 

 stretch the wires (tig. 196). 



The log which is to descend the wire, is suspended from it 

 by chains from t^'o wheels {a a fig. 197) running on the wire 









and kept at a suitable distance apart by a rod (/>). This 

 arrangement is termed a truck. Were the laden truck left to 

 itself, it would descend with constantly increasing velocity down 

 the wire, and smash the wood and itself at the end of its course. 

 In order to prevent this and control the course of the truck, a 

 second and more slender wire (*S' fig. 197) is attached to the rod 

 Qi), and is wound round two rollers at the upper end of the 

 tramway, so that the truck may be let-down and drawu-up again 

 empty. These rollers also serve as a break to regulate the speed 

 of the truck. 



The wire- tramway in the Grindelwald, which is shown in 

 figs. 195, and 196, is 4,300 meters (say 14,000 feet) long, and 



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