384 SPENCER : THE YOllEDALE AXD MILLSTONE GRIT ROCKS. 
It is generally a thick, rough, false-bedded grit of from 70 to 
100 feet in thickness, with flagstone and building stones at the base. 
The Flagstone group varies in thickness from 12 to 60 feet, 
and is divided from the Rough Hock by a bed of shale of from 
8 to 20 feet in thickness, but at Halifax this shale is generally 
absent. 
In Derbyshire the Flagstone is divided from the Rough Rock 
by a much thicker bed of shale and is termed by the Geological 
Surveyors their 2nd Grit rock. But the writer has shown in 
a former memoir"" that the Flagstone in our neighbourhood is really 
part of the Rough Rock which gave off Flagstone beds at intervals 
as it was laid down. 
The Rough Rock in many places yields good building stones 
and forms most excellent materials for curbs and setts for our 
istreets, while the underlying Flagrock 3'ields some of our best flags 
and building stones. 
In some places, in the middle of the Flagrock, the flags have 
been laid down at a different angle to the beds above and below. 
A case of this sort occurs in the Moor End Quarries, and other 
cases of a similar character are not infrequent. One of the best 
examples we have seen was taken from a railway cutting on the 
branch line from Xorth Dean to 8tainland. A white grit of from 
20 to 30 feet in thickness was exposed in the cutting ; in the midst 
of the rock a series of flags and thin shales were laid down at an 
angle of about 22^- degrees. The beds extended all through the 
cutting, a distance of about 200 or 300 yards. 
Description of the Strata alon(; the Line of Section I. 
Section 1. proceeds from the Halifax coal strata of Ringby 
Hill, two miles north of Halifax Town Hall, across the Rough 
Rock of Ovenden to Camp End (Warley Edge), thence through 
the Third Grits down to the Calder near Cooper Mill, half 
a mile east of Luddendenfoot. Here it cuts through the Kinder 
Grit which has been brought to the surface by a fault. The section 
* Trans. Manchester Geological Society. 
