386 SPENCER : THE YOREDALE AND MILLSTONE GRIT ROCKS. 
that great upheaval. It is only when we get a little further 
away from the Pennine Chain that the dip assumes a general 
north-west and south-east direction. 
The Character and Thickness of the Strata Shown in 
Section I. 
The Rough Rock and flagstone and intermediate shales under 
Ovenden and Halifax, IS'orland and Greetland Moors have a 
thickness of about 150 feet, and the shales below are about 150 
to 200 feet. In these shales is a bed of marine fossil shells 
containing Aviculopecten, Posidonomya, and Goniatites, these being 
the most common fossils in all the Millstone Grit shales, besides 
many other shells and fish remains. This fossiliferous bed has 
been exposed in several places in the district, and has yielded 
to the writer between 20 and 30 species. Towards the base of 
the shales is a bed of coal about six inches in thickness, having 
under it a bed of seat-earth. 
On the summit of Crow Hill in Sowerby is an outlier of 
these shales, crowned by about 12 feet of flagstone. 
The Third Grits may be regarded as intermediate beds or "middle 
grits," which occur in the great mass of shales between the Rough 
Rock and the Kinder Grits. The beds A and T> are fairly persistent 
over a large part of our district, but the bed A, which is a typical 
grit under Cold Edge, becomes deteriorated in AYheatley valley 
and other places into raggy shale. The beds B and C are of 
a lenticular character, and seem to thin away into rag and shale 
now and then and come in again, but often at diff'erent horizons, 
in the shale, rendering it a difficult task to correlate them in 
different localities. The total thickness of the Third Grits in Calder- 
dale in the line of the section is about 600 to 700 feet, but 
further west the lower beds seem to increase in thickness. 
The average thickness of the Third Grits of the Section. 
A 40 feet, shales 100 feet = 140 feet. 
B 60 „ „ 100 „ =160 „ 
C 50 „ „ 100 „ =150 „ 
D 80 „ „ 150 „ =230 „ 
