TIMBER-SLIDES. 



:3-25 



massive to preserve their own stability cau these props he dis- 

 pensed with. The lowest section of a slide is very strongly made 

 to resist shocks, and is either horizontal or inclined upwards, 

 in order to moderate the fall of the wood as it slides-down. It 

 should rest on strong blocks of wood driven into the ground, and 

 the effect is to shoot the descending piece of wood upwards in a 

 curve, so that it may fall without any great shock (fig. l(jO). 



As a rule (fig. 166), each section consists of six poles, two 

 {a a) forming its base, two {h h) the sides, and two (c r) the edges 

 of the slide. In curves, one of the pieces <: may be omitted on 

 the inner side. Where the gradients are very steep a second 

 pair of poles {d d) may be added. The wood on the inside of 

 the slide is all barked. 



The different sections of the slide are joined together as 



shown in fig. 167. The pieces {a a) tit into the groove of the 

 block-sleeper (fig. 168), the pieces {h J>) rest between the former 

 and pegs driven into the block- sleeper, and (e c) on these pegs 

 and two others similarly fixed ; they^are also kept in place by 

 props [w), (d d) when used are similarly supported. 



The construction of slides in the Black Forest is somewhat 

 different, as shown in fig. 169, where all the poles, except the 

 two lowest, are bored by augers, and kept in position by strong 

 beech trenails. In some cases a plank is used for the bottom of 

 the slide. 



The trestles which support the block- sleepers vary in height, 

 according to the nature of the ground, or the block-sleepers may 

 rest directly on the ground. 



In the Black Forest and the Tyrol, the block-sleepers tisually 

 rest on round billets. 



