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LAND-TKAXSPOKT. 



Section III. — Timber-Slides. 



A timber-slide is a more or less permanent channel, either 

 constructed of wood or excavated in the ground, and placed 

 aloncf a mountain slope ; the wood descends in it hy its own 

 weiiiht. Slides may be distinguished as wooden slides, gi-oimd 

 C3lides, or roads used for sliding timber. 



1. ]]'ooi]rtt Sluh'S. 



Wooden slides may be constructed either of butts or poles, or 

 of planks. 



(a) Log or Pole Slides. — These are semi-circular channels, 

 made of closely-nacked poles, or logs, 4 to 12 inches thick, and 

 are used for timber transport. The pieces of timber used in con- 

 structing ordinary slides of this kind should be IG to 26 feet long, 

 and the separate sections of which the slide is made are the same 



Fig. 166. 



length as the pieces. The length of a slide is thus frequently 

 described by the number of sections it contains. The channel 

 has a width of 2i to o feet ; it rests on strong wooden supports, 

 Avhich may be termed block-sleepers, and are made of ditferent 

 shapes. Owing to the great Aveight of the slide, which naturally 

 tends to drag it down-hill, this tendency being increased by 

 the shaking to which it is subject Whilst sliding is in progress, 

 the block-sleepers must be supported by props on both sides to 

 keep them steady. Only when the block-sleepers are sufficiently 



