110 FORESTS, WOODS, AND TREES 
part of which is mixed with dark humus, passing at the surface 
into a very thin layer of acid dry peat. In most heaths a hard 
‘pan’ forms at some distance below the surface of the soil. 
In north-east Yorkshire there are heaths at a high 
elevation, between 800 and 1250 feet, which are developed 
on a few inches of humous sand, covered by two or three 
inches of sandy peat, and passing down into sand. These 
heaths, inasmuch as the dominant vegetation is heather, are 
popularly called moors, and are used for preserving grouse ; 
but they differ from the heather moors of the Pennines and 
of the Dublin Mountains, which rest on pure peat of a 
considerable depth. 
Similarly in the central and eastern Highlands of 
Scotland, namely, in the basins of the Tay, Dee, and Spey, 
there are immense heaths, between 500 and 2000 feet 
elevation, which are colloquially termed moors and are used 
for grouse shooting. These heaths are somewhat inter- 
mediate in character, as the heather grows in a greater 
depth of surface peat, four to eight inches, than occurs in 
the English heaths, but, like the latter, they are developed 
on sandy or gravelly soil, in which acid peaty humus has 
accumulated. At a depth of one to two feet there is 
often a layer of moor-pan. 
Heaths are much drier than heather moors, e for 
purposes of afforestation must be considered quite distinct 
from the latter. Extensive wild and cultivated forests of 
Scots pine occur on the heaths of the Scottish Highlands ; 
and this species, if unchecked by man, would speedily 
colonise the heaths of the south of England. Heaths are 
thus very suitable for plantations of conifers, especially 
of pine and larch, the only hindrance being exposure to the 
wind where the land is at a considerable altitude and not 
protected by surrounding high mountains. Heather moors 
are not so favourable for afforestation on account of the 
depth and wetness of the peat, on which trees will rarely 
grow big enough to yield commercial timber, unless the 
situation is sheltered and the peat is drained. 
Above the zone of heather moor, the peat usually 
