The Work of Construction 19 



as before, until the desired height is 

 reached. The height is entirely arbitrary, 

 but some points should be at least as high 

 as the line of vision, as one of the great 

 advantages of a rock garden is the pleas- 

 ure of enjoying some of the typical rock 

 plants without stooping. The rocks used 

 as fillers should overlap here and there 

 to give strength, but care must be taken 

 to contrive plenty of long soil runs. 

 Eighteen inches should be the very least, 

 A plant like the alpine androsace is a tiny 

 rosette, seemingly requiring no more than 

 an inch or two of soil, but its roots are 

 likely to be found following an earth- 

 filled crevice in the rocks to the depth of 

 a yard or so. It is because of this deep 

 penetration of roots that the soil should 

 be packed so very firm ; the roots must be, 

 in no danger of loose soil or of striking 

 a hidden hollow. 



