69 
exactly corresponding to that of the Silkstone coal, and 
which, for this reason, the author considers to be the equiva- 
lent of that seam. The Blocking coal, however, differs 
totally from the Silkstone in character, for it is a single bed 
of coal averaging 1 foot 6 inches in thickness, and reaching 
but rarely an extreme thickness of 2 feet. 
After the above general sketch, the author gave the 
following details of the variations of the Silkstone coal : — 
About nine miles south of Rotherham the seam consists 
of two beds of moderate thickness, with a thin dirt parting. 
The section being 
Ft. In. 
Coal 1 n 
Dirt 0 8 
Coal 1 9 
About six miles north-west of Rotherham, where the 
seam may be said to be about at its best, it consists of the 
following subdivisions : — 
Ft. In. 
Branch Coal 12 
Coal 1 4 
Dirt 0 7 
Coal 3 7 
About three miles to the west of Rotherham the parting 
of dirt has increased to a thickness of from 1 foot 3 inches 
to 4 feet, the top and bottom coals having a little less than 
their ordinary thickness. C, Plate II., Fig. 1. 
Going on towards Chapeltown, the dirt parting continues 
to swell out till it reaches a thickness of ten yards. A little 
further on another singular change comes over the seam, the 
lower bed of coal decreases in thickness and passes into a 
mass of black shale with thin shreds of coal, the top bed 
still retaining its average thickness. D, Plate II., Fig. 1. 
The exact area over which the bottom seam is wanting has 
not been ascertained, but its disappearance is certainly only 
