88 rastall : the ingletonian series of w. yorkshire. 
Stratigraphy. 
The Ingletonian rocks in the sense here defined cover a 
considerable area on the floor of the valley of Chapel-le-Dale, 
to the north of the northern branch of the Craven fault : an- 
other considerable exposure occurs in the Ribble valley, in 
the neighbourhood of Horton-in-Ribblesdale, and in the Geo- 
logical Survey map the same series is indicated in the upper 
part of the Crummack valley, though the exposure here is very 
obscure, owing to drift and peat. 
The valley of Chapel-le-Dale possesses several remarkable 
features : in its upper part it is wide, with a very gentle fall, 
but at a point about a mile above Ingleton its character utterly 
changes. The river plunges down suddenly into a most ex- 
traordinary series of deep gorges, with rapids and waterfalls. 
These gorges have obviously been formed for the most part 
by the coalescence of a number of gigantic pot-holes, since the 
peculiar outline thus produced is very clearly seen in some of 
the deeper pools ; this mode of origin often causes the walls 
of the gorge to overhang to a considerable extent, and the whole 
forms a scene of great beauty. 
The geological structure of the Chapel-le-Dale valley above 
the Craven faults is exceedingly simple (see Map, Plate VII.). 
Its whole floor is occupied by pre-Carboniferous rocks, striking 
approximately N.W. and S.E., that is at right angles to the 
course of the stream, and dipping at very high angles, usually 
departing but little from the vertical ; but where the beds are 
inclined, they usually dip to the S.W., in a few cases only to 
the N.E. However, in the walls of the gorge, which are some- 
times 50 feet or more in height, it can often be seen that the 
beds dip alternately to one side or the other of the vertical, 
even in this comparatively small depth, so that observations of 
dip on the surface are obviously of little value. Similar beds 
are also exposed in the lower part of Kingsdale, the valley of 
the Swilla, from Manor Bridge up to Thornton Force. These 
older rocks are overlain by practically horizontal Carboniferous 
Limestone. The unconformity, which is very striking, is clearly 
seen in many places on the sides of both valleys, and it is 
