ch in FIXATION OF UNSTABLE SOILS 293 



A simple method of giving a check to the movement 

 of the surface particles of the soil is in pegging down, 

 on the slopes, branches of trees, the butt-end being- 

 placed down the slope ; or, if small trees or bushes are 

 already growing on it, a method similar to that adopted 

 in hedgerows in parts of England can be employed. 

 The tree is partly cut through and bent flat up the 

 slope and pegged clown (Fig. 92). Some trees, when 

 thus pegged down, have the faculty of giving out 

 adventitious roots at the points of contact with the 

 soil, and of thus holding it in other words, layers are 

 formed. The assistance of cuttings can also be obtained, 

 not only put in all over the surface, as is done with 

 Robinia in railway cuttings in Europe, but by using 



^3U= 



Fig. 93. 



them as the uprights for wattle - fences constructed 

 across the face of the slope. There must, of course, 

 be sufficient moisture in the soil to make these cuttings 

 a success. Where there is not, fences are made with 

 posts of strong lasting timber, any long flexible branches 

 serving for the purpose of binding them together 

 (Fig. 93). These fences are put up horizontally along 

 the contours, the distance between the rows of fences 

 varying with the gradient and with the stability of the 

 slope surface. Logs of timber may also be laid hori- 

 zontally across the slope and made firm by means of 

 strong posts. Where the slope is very steep and the 

 surface very unstable, it will become necessary to have 

 revetment walls of dry masonry. If these have to be 

 made of any considerable height they may be set up in 

 steps, the flat surfaces between the steps being planted 

 up with suitable trees or with cuttings (Fig. 94). 



