354 
PROCEEDINGS, 1871 — 1877. 
into several beds, which become thinner still towards the north-west, 
and in this part no attempt has been made to work it. Still farther 
northwards there is a workable coal known as the Blocking coal, which 
holds a position in the measures exactly corresponding to that of the 
Silkstone coal, and which Mr. Green considers to be its equivalent. 
The Barnsley coal is distinguished by the occurrence in it of a band 
of hard or steam coal, lying in the middle of the seam, in the neigh- 
bourhood of Sheffield. The coal ranges from 4 feet to 4 feet 6 inches 
in thickness ; its thickness increases northwards, and at Rotherham 
reaches 7 feet or 8 feet ; whilst about Barnsley, where it is at its best, 
the thickness is between 9 feet and 10 feet. At Darton, a parting of 
dirt set in, and still further northwards at Crigglestone, it becomes split 
up into so many small seams by dirt partings as to be quite worthless. 
Beyond this point w^as unexplored ground, but on approaching Wake- 
field, the coal called the Warren House, probably corresponds with 
the Barnsley. It is for the most part a mixture of thin bands of coal 
and dirt, whilst, north-west, a coal called the Gawtliorpe, a seam 
from 2 feet to 3 ft. in thickness, is probably the equivalent of the 
Barnsley coal. The author gave detailed sections of the coals in 
several parts of the district, and explained the method by which the 
coal becomes divided into thin beds by intercallations of dirt and 
shale during its formation. 
Professor Green also contributed a paper on the Geology of the 
central portion of the Yorkshire Coal-field, lying between Pontefract 
and Bolton-on-Dearne. This is one of the least known portions of 
the Yorkshire Coal-field. Its edges are pierced by workings to a 
small extent, but the larger part of the tract remains unpierced by a 
single shaft or bore-hole. The south-western boundary of the dis- 
trict is formed by the outcrop of the seam of coal known as the 
Shafton, Billingiey, Denaby or Nostell Top Coal, which lies some 430 
yards above the Barnsley Bed. A line of fault, ranging from Royston 
Station to Pontefract, bounds it on the north-west ; on the up-cast 
or north-western side of this fault, collieries are plentiful, but on the 
down-cast there is no information from actual exploration beyond a 
few unimportant bore-holes. The country for some distance is flat 
and tame, but two tracts, one extending from Clayton-in-the-Clay 
