172 
PHYSICAL GEOGRAPHY 
are caused by gritstone layers ; the same is the case in Aldstone 
moor; the finest in Wensleydale are in the Hardrow limestone, or 
scar limestone of Aldstone moor. 
Millstone grit series — The great extent of surface occupied by this 
thick mass of arenaceous and argillaceous deposits renders it an impor- 
tant element in the scenery of the mountain districts of Yorkshire. 
Usually seen on high ground, where the coldness and humidity of the 
atmosphere favours the growth of heath, sedgy grass, and mosses, and 
almost extirpates other vegetation, these rocks commonly form a sur- 
face of dreary moorlands, far less serviceable to the agriculturist than 
much loftier hills in the slate district of the lakes. Under this brown 
covering, the grits and shales are equally concealed, except where some 
torrent or waterspout has ploughed deeper than usual. But the edges 
of these dreary surfaces commonly shew at least the coarser grit rocks, 
in bold broken craggy edges, easily known at great distances from the 
continuous vertical ‘ scars’ of limestone. Thus the millstone grit of 
Arkendale and the Ingleborough grit are seen and recognized in the 
brows and sides of many western mountains. The upper grit of 
Brimham appears in the east usually on the summits and at the pro- 
minent points of lower hills, much as in Derbyshire. 
y 
The waterfalls in the grit rocks are not numerous yet sometimes (in 
Arkendale and Swaledale) pleasing, though deficient in wood. The 
wasting power of the atmosphere is very conspicuous in these rocks: 
seaiching out their secret lamination ; working perpendicular furrows 
and horizontal cavities, wearing away the bases, and thus bringing a 
slow but sure destruction on the whole of the exposed masses. The 
rocks of Brimham are in this respect very remarkable, for they are truly 
in a state of ruin, those that remain are but perishing monuments 
of what have been destroyed ; and it is difficult to conceive circum- 
stances of inanimate nature more affecting to the contemplative mind 
than the strange forms and unaccountable combinations of these gigantic 
masses. In their decay the works of nature have an instructive simili- 
tude to the ruins of human constructions, and suggest inquiries of the 
