PROCEEDINaS OF GEOLOGICAL SOCIETIES. 
263 
there is another coal, called the "bassey mine," lying about 30 yards 
above it. 
At Birchinley, near Rochdale, the coals still retain the same names, and 
also at Dearnley and Clegi^swood. Passing on through Whitworth and 
Wardle to Bacup, the 40-yards mine takes the name of the little or top, or 
half-yard mine. At Whitworth, AYardle, etc., portions of the Gannister 
coal, where it originally crop-^ed out all round some of the hills, have been 
entirely worked out, and small workings are commenced on the lower foot- 
mine. The Gannister coal at Bacup is called the 3'ard, or main coal ; the 
lower foot and the sand-rock mines still retaining their names. 
Up to this point there is no difSculty whatever in following the order in 
which these coals He. The strata follow each other with surprising regu- 
larity, seldom varying more than 10 yards in thickness between the same 
coal-seams. 
About a mile and a half to the north-east of Bacup one of the large faults 
passes in a north-westerly direction, causing some alteration, and at the 
opposite side of that the principal coal of the Gannister series is known at 
Cliviger and all round the northern part to Colne as the " mountain four 
feet," and it is there generally accompanied by an unusually large number 
of very fine specimens of Goniatites and other fossil remains. 
Eeturning to the south-west side of the large fault, between Bacup and 
Cliviger, the Gannister coal, which was at Bacup 4 feet thick, becomes much 
thinner in a westerly direction. 
At Over Darwen the Gannister coal is called the "lower," "70 yards," or 
•* half-yard " bed. The principal seam above it is there known as the "yard 
coal," which, together with the " little coal " above it, corresponds with the 
"40-yards " seam. The flag and tile-rock of Darwen lies about 40 yards 
above the " yard coal." The strata, about 10 yards in thickness, which se- 
parate the "little coal " from the " 3'ard coal," at Darwen, gradually thin out 
in the direction of Hoddlesden. At the old Hoddlesden Colliery the two 
seams were found gradually approaching each other until they came so near 
as to be worked together ; and now, where they are being worked, there is 
only a division of black earth between, the rock being entirely nipped out. 
They continue together as one seam for some distance, but ultimately they 
divide out again, and at Belthorn the upper part is called the " half-yard," 
and the lower the "little coal." At Brookside and Duckworth Hall they 
again lie together, and are called the " Poor Eobin " bed. At Chorley, and 
also at Heath Charnock, the corresponding coals are known as the '"little" 
and the " higher mountain." At many of those places this "little" coal has 
a rock floor, which has often been mistaken for the true Gannister. 
The total thickness of the strata between the Gannister coal and the 
Arley mine is, at Oldham, about 3(X) yards. At Simpson Clough it seems 
to be thinner than at an}" other point, being onl}' about 253 yards. At 
Clayton, the distance is about 308 yards from the Arley to the Gannister. 
Adding to this the total thickness of strata in which coal-seams are found 
below the Gannister, namely, 326 yards, as shown at Mossley and Harts- 
head, gives a total thickness of about 625 yards of coal-bearing strata in 
the lower or Gannister series alone. 
The middle scries, from the Arley mine to the Worsley four-feet, is about 
975 yards in thickness. The upper series, above the Worsley four-feet, 
has been proved at Patricroft to a thickness of 390 yards, but this is not 
the whole of it, and including the measures at Clayton, near Manchester, 
it is about 550 yards in thickness. The total thickness of coal-measures 
in the upper, middle, and lower series, to the lowest coal-seam, is therefore 
about 2150 yards, exclusive of the grits and limestone shales below. 
