spencer: the yoredale and millstone grit rocks. 381 
the crown of the tunnel being carried through the bottom bed of 
the series. From the west end of the tunnel the line runs in the 
same bed of shale as far as Mill House, where a lower bed of 
grit — the top bed of Kinder — makes its appearance in the cutting. 
A short distance further up the line a fault crosses it, which throws 
down the Kinder so that the top beds of the rock abut against the 
lowest bed. In these upper beds — composed of shale, rag, and 
stone — is the usual thin seam of coal, here about six inches in 
thickness. About half-a-mile further up, at Rough Hirst, a cutting 
shows the coal running along on the east side of the line for some 
distance, nearly on a level with the rails. At Little Haven, another 
fault crosses the line diagonally in a north and south direction, 
which throws the rock up to the east about 50 feet. Near 
Ripponden, a fault throws the rock down out of sight, but it soon 
begins to rise again and occupies the bed and sides of the brook, up 
as far as the bottom of Butts Clough, where it is throw^n up to the 
soutli by another fault. At Slitheroe Bridge the top beds of the 
Kinder, with the usual bed of coal, are exposed. The Kinder Grit 
occupies a large area in Booth Dean, where it rises with the slope of 
the ground up to the top of Blackstone Edge. 
Third Grit Rocks. 
The Third Grits occupy an extensive area on each side of the 
river Calder. " These middle grits " were divided by the Geological 
Surveyors into four divisions, and named A, B, C, and D, D being 
the lowest and A the highest bed."^ 
In their memoir on the " Geology of the neighbourhood of 
Dewsbury, Huddersfield, and Halifax " the order of the letters is 
reversed, A being applied to the lowest of the Third Grits and D 
to the highest. It is of little consequence which order is adopted 
so long as the reader knows to which rock each letter is applied. 
Being accustomed to the use of the first method, that method 
will be adhered to in this paper. The D grit is a most variable 
rock both in quality and thickness. 
Geology of the Burnley Coal Field. 
