4 VEGETATION OF THE PEAK DISTRICT [CH. 
The hill slopes of the Coal-measures are rarely very steep, 
and are characterized by a number of typical oak (Quercus — 
sessiliflora) woods which are at least semi-primitive in character. 
These woods occasionally spread out for a little distance on to 
the low, flat or gently sloping plateaux. The valley bottoms 
are almost filled up with overgrown, manufacturing villages, 
many of which have a population of twenty thousand people. 
The smoke from the villages and hamlets, for even every 
hamlet has its factory, frequently renders the sky dull and 
the atmosphere thick and heavy. Sandstone walls as a rule, 
hedgerows occasionally, separate the cultivated fields; and the 
stone walls and the tree trunks are permanently blackened with 
soot and smoke which have effectually, destroyed almost all 
traces of mural plants, especially Cryptogams. Only in the 
heart of the woods, some of which retain their original sylvan; 
character, may one, in this Coal-measure country, forget the 
propinquity of coal-mines and mills. 
The higher hills of the central masszf consist of sandstones . 
and shales belonging to the Millstone Grit and to the Yoredale. 
or Pendleside (Hind, 1897, etc.; Hind and Howe, 1901) series of 
rocks. -Here there are fewer factories than on the Coal-measures, 
and no coal-pits. The higher hill summits are unpopulated, 
and covered with peat moors. Here and there, the moorland 
plateaux terminate abruptly in precipitous escarpments, locally 
known as “edges,” formed of massive sandstone rocks. The 
larger and broader valleys are known as “dales,’ the smaller | 
and narrower ones as “cloughs” or “deans,” or, further north, 
as “ghylls.” The upland valleys shelter woods of oak (Quercus, 
sessiliflora), and. rarely of birch (Betula pubescens); but more 
frequently, the slopes of the steep valleys are tenanted by. 
scrub or, grassland. The bracken is a characteristic plant of, 
the drier slopes. The upper portions of the cloughs contain , 
numerous reservoirs (see figure 36) which are fed by the 
streams issuing from the peat moors of the plateaux. The 
lower plateaux and valleys are cultivated, chiefly as perma- 
nent pasture: arable land is decidedly scarce: wheat, in 
particular, is very rarely grown; and even fields of oats are 
uncommon. The fields are usually separated by sandstone 
walls; though, as in the Coal-measure country, hedgerows 
occur where the shales are of great extent. 
