120 ROCK GARDENS 



ing wall is very similar to that used in the 

 construction of the division wall, I think it 

 would be better to deal with each separately, 

 and afterwards I will show what can be done 

 to metamorphose the old wall. 



The main principle underlying the construc- 

 tion of retaining walls made for the purpose 

 of growing rock plants is to place the stones 

 in such a way that all available moisture be 

 directed back towards their roots. For this 

 reason, and also because additional strength 

 will be obtained, the walls should not be built 

 perpendicular, but should rather slope back 

 from the foot at say an angle of 60 degrees. 

 Fairly flat stones may be used, and it will 

 simplify the building if they be of much the 

 same thickness, for then the " courses '' will 

 work in evenly. These stones should be firmly 

 fixed and should all slope down towards the 

 back. The lower stone should slightly 

 protrude beyond that immediately above it, in 

 order to catch the rain falling from it. No 

 mortar should be used, but soil only, and not 

 very much of that — just a sprinkling between 

 each course of from ^ to ^ inch thick ; if 



