326 WOOD TRANSPORT BY LAND. 



precipitations affect the surface of the slide, and modify the 

 necessary gradient very considerably. 



However desirable it may be to give to each slide the most 

 suitable gradient, the nature of the ground frequently renders 

 this impossible, and the gradient is thus consequently greatly 

 modified. As a rule, by using the sides of a mountain 

 torrent, these slides run more or less directly down to the 

 lower valleys, at whatever gradient the bed of the torrent may 

 render practicable. Slight changes of gradient over a few 

 sections of the slide must be avoided, however, by levelling the 

 base of the slide, either by cuttings, embankments, or con- 

 structing viaducts, so that the vertical section of a slide may 

 represent a gradual descent, and there should never be any 

 decided angles between two connected sections. [Plate IV. 

 shows a slide crossing a mountain ravine in the Himalayas. 

 -Tr.] 



It is also necessary to secure steeper gradients in the higher 

 portion of the slide than for the lower portion, so that the 

 latter may more and more approach the horizontal direction ; 

 the last few sections of it may even ascend, and the longer 

 the slide and the heavier the pieces to be sent down, the more 

 this must be accentuated. As regards the horizontal plan of 

 a slide, it should be straight or form a steady curve without 

 sharp corners, especially for long logs. 



(e) Collecting-places for Wood. In high mountainous 

 districts the configuration of the ground will not allow always 

 of the construction of a continuous slide from the lofty ridges 

 down to the valleys, and several transport-works may be 

 made, such as sledge-roads, slides, wire-tramways, etc., accord- 

 ing to the nature of the ground in each part. In order to 

 collect the wood coming down from one side to another lower 

 one, a collecting-place may be constructed. It is barred with 

 stout poles with side palisades and has an aperture below, 

 into which the expanded upper end of the next section is 

 inserted to receive the wood for the next stage of the descent. 



(f) Maintenance of Wooden Slides. Wooden slides are 

 either permanent or temporary, the former serving a certain 

 forest tract for a series of years, or connecting a collecting 

 depot high up in the mountains, to which the wood is brought 



