8 VEGETATION OF THE PEAK DISTRICT [CH. 
district only contain from 0:02 to 0:04 per cent. of lime. The 
soil is usually rich in humus, and therefore retentive of water. 
Over such soils, if left uncultivated and undisturbed, peat 
inevitably develops in course of time. 
The sandstones and shales are usually regarded as having 
been originally formed from the waste and denuded material 
of a great tract of granite. The resulting soils are of a siliceous 
nature, very deficient in soluble mineral salts, whilst in texture 
they are intermediate between loam and clay. The soils are 
shallow, as in the case of practically all siliceous soils derived 
from the Palaeozoic rocks; and the most typical vegetation 
consists of grassland dominated by the mat-grass (Nardus 
stricta) and the silver hair-grass (Deschampsia flexuosa). 
There is a popular but quite erroneous impression that the 
soils over the rocks of the Pendleside (or Yoredale) series of 
the southern Pennines are calcareous ; and, in Linton’s Flora of 
Derbyshire (1903), the plant records are partly arranged on this 
assumption. The error may perhaps be accounted for by the 
fact that the true Yoredale rocks of the northern Pennines are 
frequently calcareous, and by the additional fact that, on the 
existing Ordnance maps of the Geological Survey on the scale 
of a quarter of an inch to the mile (1: 253,440), the rocks of 
the Pendleside series and those of the Carboniferous Limestone 
are indicated by the same colour. It is true that the Pendle- 
side rocks of the southern Pennines occasionally show thin 
bands of calcareous nodules; but these bring about little or 
no change in the vegetation. 
The soil over the Carboniferous or Mountain Limestone is. in 
general, strongly calcareous, as this rock 1s composed very largely 
of molluscan shells, encrinites, and corals ; but it agrees with that 
over the sandstones and shales in often being highly ferruginous, 
and in giving, from place to place, a great range of variation in 
water content. The highest percentages of calcium carbonate 
occur on the steep hill slopes; and this is no doubt due to the 
continuous exposures of new surfaces by denudation. The 
lowest percentages occur on the flatter plateaux; and this is 
doubtless caused by the leaching of the upper layers of the soil, 
the lime being carried away in solution to the subterranean or 
telluric waters, which find a ready means of escape to lower 
levels by means of the open joints of the limestone. 
