TIMBER-SLIDES. 323 



As Fig. 201 shows, they are made generally with eight hewn 

 poles, the sides of which fit closely, and the interstices are 

 stopped with moss, or with tarred tow, etc. 



[A wet slide in the Deota Forest in Tihri-Garhwal in the 

 X. W. Himalayas was constructed in 1876-78, heing 12,192 

 feet long with a fall of 1,300 feet, the gradients from 1 in 14 

 to 1 in 2*5, and the best gradient 1 in 4. It consisted of a trough 

 composed of three planks (12 feet X 13 inches X 5 inches) 

 roughly joined and firmly wedged into block-sleepers. Being 

 made of Pinus lonyifolia, the latter only last 3 or 4 years, but 

 should be made of deodar- wood, which is very durable in the hill- 

 districts of India. The slide is worked by means of a good flow 

 of water, which is supplied by troughs at intervals of about a 



Kijr. L'nl. Wet slide. 



quarter of a mile, a good depth of water being required when 

 the gradient is less than 1 in 3. When there is plenty of 

 water, 1,200 railway-sleepers can be passed down in about 10 

 hours, each sleeper taking ten minutes on its journey. Such 

 slides cost about 16rf. a yard in India.* Fig. 202. Tr.] 



For short wet slides, where there is a plentiful supply of 

 water, preference should be given in their construction to merely 

 hewn poles, instead of planks, as repairs are thus facilitated. 

 Water is brought into the slide whenever it passes any stream 

 or spring. In the Salzkammergut, planks are used in a similar 

 way to the Tihri-Garhwal slide. In California, hundreds of 

 miles of wet timber-slides have been constructed as shown in 

 Fig. 203. 



* An account of this slide is given in the working-plan of the Tihri-Garhwal 

 Forests by N. Hearle, published at Allahabad, for the Government of the N. W. 

 Provinces, l.xxs. 



Y 2 



