382 SPENCER : THE YOREDALE AND MILLSTONE GRIT ROCKS. 
On Erringdon Moor, south of the Calder, it is upwards of 
300 feet in thickness " and faces westwards with a splendid 
escarpment of conglomerate, passing upwards into flagstone." A 
large bay has been scooped out of this massive"^ grit rock, in 
Crag valley, called Broad head Clough, which is strewn with large 
blocks of grit, " which is here of so coarse and massive a character 
as to resemble the typical Kinder Scout Grit."* 
This D grit occupies an extensive range along the sides of 
the Calder valley and its tributaries. It has generally a strong 
grit on the top, and a thick bed of galliard rock at bottom, 
with intermediate beds of shale and stone, and two thin seams 
of coal. 
Hathershelf Scout, near Mytholmroyd, is formed of this rock, 
which is there nearly 200 feet thick, with a bed of shale 20 feet 
in the middle, and two thin seams of coal. It occurs also in 
great thickness at Sowerby Bridge Station, and in the cutting 
to the east, where it gradually sinks below the surface. 
A bed of shale, varying in places from 40 to 100 feet in 
thickness, overlies the D rock, and upon the shale lies the 
C rock, which is usually a flag rock of varying thickness, and 
has been worked in various places in the district. This rock is also 
overlaid by a bed of shale of about 80 to 100 feet in thickness. 
We next come to the B grit, which is a very important 
rock in some places, but, like the C rock, it is liable to thin 
away in places and then come in again. On Wadsworth and 
Midgley Moors, and also at Deep Clough and other places in the 
Luddenden valley, it has been worked for flags and building 
stone. 
This B rock is at Deep Clough, opposite Castle Carr, about 
60 feet thick, and is overlaid with a rough grit rock. It 
yields good building stones and flags. It is interesting to the 
geologist on account of the large number of fossil plants which 
Burnley Coal Field, p. 117. 
