94 rastall : the ingletonian series of w. yorkshire. 
The Slates. 
The rocks described in the preceding paragraphs show 
comparatively few signs of crushing, but many of the finer 
sediments have taken on a very perfect cleavage, so that they 
have been extensively worked for roofing-slates. However, 
the quarries are now abandoned. The slates of the bands in 
the gorge, though not identical in appearance, are so similar that 
one general description will suffice for all. They are all well- 
cleaved slates, which split readily into thin slabs in a direction 
parallel to the original bedding, and other less perfect cleavages 
or joints divide them up into blocks of moderate size. The 
colour is either a bluish-grey or more commonly some shade of 
green, usually with a slightly olive tinge and somewhat silvery 
lustre. Some specimens show blackish dendritic markings on 
the cleavage faces. Under the microscope these slates are seen 
to consist of exactly the same minerals as the grits, but in a 
much finer state of division. Where heavy minerals occur 
they are often arranged in parallel layers, due to a process of 
sorting by current action. Here the evidence of rearrangement 
under pressure is more distinct, and the flakes of mica are usually 
seen to be bent round the grains or quartz and felspar. 
The above descriptions apply to the great majority of the 
beds, both slates and grits, and other intermediate types, which 
are exposed both in the valley of ChapeMe-Dale and in the 
neighbourhood of Horton. But there are a few special rock- 
types which need separate discussion, since they are the most 
significant of all, though forming but a small proportion of 
the total mass. The most important of these are the coarse 
grit or conglomerate, which is worked at the Ingleton " Granite " 
Quarry, and the conglomerate of Row End, Horton. 
The Conglomerate of Twisletox Dale House axd the 
Granite Quarry. 
The manner of occurrence of this rock, which is known 
commercially as the " Ingleton Granite," has already been 
mentioned. It is well exposed in the large quarry of the Ingleton 
Granite Company on the eastern side of the vaUey. It is difficult 
