620 



PROTECTION AOAINST AVALANCHES. 



rock}' slope, which may afterwards ])e sown with grass, or 

 planted with trees or shrubs. 



((■) ]]'(iUs. — On stony ground, walls of dry masonry may be 

 erected instead of wattle-fences; their mode of construction is 

 shown in Fig. 282. On steep rocky slopes, the rock must be cut 

 to admit the foundation of these walls, but this need only be 

 deep enough to prevent the walls from falling, owing to their 

 own weight. Such w-alls have proved effective in the Swiss 

 cantons, Uri, GraubUnden and Wallis, and cost 3s. to 6.s. per 

 cubic meter. Confidence in them was greatly disturl)ed by 

 the damage since 1867, done in 1887-88. 



I'ii;. 



