32 
DESCRIPTION OF TFlE ROCKS 
4. If now we turn to Coverdale, we shall find the Parkhead lime- 
stone universally exhibited in its whole length, always thinnest on the 
the south-east side i the underset limestone rather unequally developed, 
and the beds below subject to much variation. 
The principles of the variation from the southern to the northern 
type in this region, are thus clearly unfolded. 
1. The great limestone series, which in Greenhow hill is one mass, 
admits between some of its upper members partings which are thin at 
Grassington and Kettlewell, but toward the west, north-west, and north, 
augment in thickness, and assume new characters. 
q There is a new group of limestone beds introduced in the upper 
part of the series, (the Parkhead limestones) which augment in thick- 
ness toward the north-west. 
3. This method of variation may be expressed in a diagram. ( See 
Diagram, No. 9-J 
The northern series. 
Lower Limestone Group. 
The lower part of the limestone formation, subject to less variation 
than the upper, fills Kettlewell dale, from Buckden downwards, turns 
up Litton dale, almost to its source, covers all the wide plateau of 
Hardflask, and forms the general base of Fountain’s fell, Coska and 
Penyghent ; thus uniting Wharfedale and Ribblesdale. The southern 
boundary of this great area passes along a line of dislocation from 
Skythorn to Malham, and, bending to the north round Ryeloaf, is 
continued to Settle. Its lofty escarpments then turn to overhang 
the Ribble, as far as Stainforth, where the slate ranges make a deep 
indentation. Beyond, it again resumes its parallelism to the Ribble, 
and, about two or three miles above Horton, fills the whole valley. 
Its widening surfaces now extend to the south and the west, so as 
