CH. Ill 



FIXATION OF UNSTABLE SOILS 295 



trained in the manner described ; it also shows the 

 wattle-fences put up for strengthening the banks, as 

 well as the horizontal, slab-covered paths. 



Where the stability of a slope is endangered by a 

 mountain torrent which is constantly undermining its 

 base, its impetus has to be checked by terracing right 

 up to its source. This terracing is done by means of 

 walls built across the bed of the stream from distance 



Fig. 95. 



to distance according to the gradient, liability to sudden 

 Hoods, and nature of the soil. 



Quite at the top it may be sufficient to substitute 

 live wattle-fences for the walls, but wherever there is 

 sudden strong pressure walls will have to be erected. 

 These walls (Fig. 96) should be put up at carefully 

 selected places, where they can rest against solid bed- 

 rock. Near the top they will be relatively small and 

 simple in construction, but they will gradually become 

 larger as the volume of the stream increases, owing to 



