182 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY, 
gradients of the ground, a continuous vegetable covering is 
often impossible. 
The protective influence of forests and turf, and the destructive 
results which follow from their inconsiderate removal, have 
long been recognised. In forest-clad hill-regions the soil-cap is 
covered with a layer of decaying vegetable matter, derived from 
the forests themselves. In the case of very old forests, this 
vegetable layer may vary from a few inches to a foot or even 
more in thickness. As it consists of a matted mass of leaves, 
branches, and fallen trunks, it is not readily removed by rain— 
the latter becoming absorbed and finding its way down into the 
soil-cap and the underlying rocks. After circulating through 
these rocks for a longer or shorter distance, it is again discharged 
as springs of clear water. But should the forest be destroyed, 
the vegetable covering of the ground will soon begin to disappear 
—the waste resulting from its oxidation being no longer made 
good by the supply of fresh materials from above. In time, 
therefore, the bared soil-cap becomes subject to the mechanical 
action of rain, which is no longer entirely absorbed—much at 
once running off and carrying with it a burden of sediment. 
Thus the soil-cap becomes reduced, and may be even entirely 
swept away. Precisely the same kind of destruction attends the 
removal of old turf from steep slopes. No doubt, even in forests 
and turf-clad land, soil is gradually being removed from higher 
to lower levels; but the process is slow, and the loss is. made 
good from the subsoil, while the latter grows at the expense of 
the underlying rocks. But when the protective vegetable cover- 
ing is removed from a steep slope, soil and eventually subsoil 
must vanish—the disintegration of the rocks, however rapid it 
may be, cannot keep pace with the washing away at the 
surface. 
| Vote.—This article will be continued in our next issue. | 
