TIMBER-SLIDES. 



329 



The middle space is filled with boulders, and the outer frame-work is 

 also packed with dry stone-masonry to give solidity to the piles. 



The largest log sent down was 48 feet long and it descended for 

 2,500 feet, at the rate of 20 miles an hour. {Vide Plate III.)— Tr.] 



(b) Plank- slides. — In plank-slides, as shown in fig. 173, the 

 base and wiills are made of planks, which are let into the block 

 sleepers, and firmly nailed to them. 



[In the Lambatatch Forest in Tihri-Garhwal in the north-west 

 Himalayas, a slide of this kind, 2| miles long, was made by simply 

 wedging together two vertical and one horizontal planks, each 

 measuring 13 feet x 12 inches x 5 inches, into block-sleepers. It 

 was used for broad-gauge railway -sleepers. This slide was 1 mile 



1,052 feet long and the fall 2,087 feet. Breaks formed of 2 and 3 

 inch planks placed 15 feet apart were used to stop the velocity of the 

 sleepers, but this proved of nu avail and the slide was then divided 

 into two sections, the steeper part being covered in with planks. A 

 little water was admitted to prevent the wood from taking fire, which 

 eventually happened to the lower part of the slide, down which the 

 sleepers went at 3 miles a minute. — Tr.] 



Plank-slides are extensively used in the Black Forest. 

 If plank- slides are to be used for the export of large quantities 

 of timber they must be strongly constructed, but when only for 

 temporary use, the sections are lightly built, and transportable as 

 shown in fig. 173. In this case the ends of the planks are 

 sloped-off and fastened by screws to those of the next section. 

 These portable slides are largely used for firewood in the Sihlwald, 

 near Zurich. 



