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 is 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. 



