136 Alpine Plants. 
pieces of stone into each mound in the course ot 
construction, to form a skeleton or hidden structural 
framework. The placing of one stone vertically 
upon another in direct contact is to be avoided, as 
they do not then “bind” with the settlement of the 
mass, but remain unstable. 
Should such an arrangement be unavoidable, as 
it is sometimes, a layer of earth should be interposed 
between the stones. It ought to be possible to step 
anywhere on the rockery without displacing the 
stones in the slightest degree. 
Unless precautions are taken to ensure this, the 
loosening of soil about the roots of the plants, even 
apart from their possible exposure, is very injurious. 
No less care should be taken in making the rockery 
to avoid leaving any cavities or lightly-packed 
spaces between stones, behind or below them, as this 
is sure to involve a serious amount of after-sinkage 
of the soil. Such care is especially necessary when 
the rockery is planted immediately or soon after 
erection, and is not left. fallow for a while to settle, 
which is much the wiser and preferable course. 
Before beginning the rockery, the bed of its 
shallower portions, if it is of any size, or the whole 
of its bed if it is very small, should be excavated 
to a depth of from rft. to 14ft. below the ground- 
level, and the bottom qin. or Gin. filled in with any 
kind of rough drainage. The soil of which a small 
rockery is to be composed should consist in the 
main of about one-third loam, one-third well-rotted 
leaf-mould, and one-third sand, the loam being 
slightly in excess. 
