82 SEVENTH REPORT—1837. 
the neighbourhood, the former dipping at the rate of about 16° and 
the latter 23°, no gradation consequently existing. At the top 
of the carboniferous strata is a series of limestones, (resembling 
those observed by Mr. Murchison at Lebotwood near Shrewsbury), 
described by Mr. Williamson in the Phil. Mag. of Sept. 1836, In- 
cluding the space occupied by these is an extent of 1400 feet 
of clays, sandstones, &c. forming the top of the series, before reach- 
ing any workable coal, when those of the small isolated coal field of 
Bradford* commence. Mr. Williamson supposes the portion of the car- 
boniferous group represented to be at least 6000 feet thick, whilst about 
400 feet more are wanting to complete the series down to the millstone 
grit of Phillips's Geol. of Yorkshire. The number of workable seams of 
coal averages about 21, having an aggregate thickness of about eighty 
feet. Towards the upper and middle portions of the series, the strata 
chiefly consist of shales, clays and sandstones, the latter often from thirty 
to seventy feet thick, and forming good building-stones, especially the 
‘Peel delph’ rock. At the depth of about 5000 feet flagstones prevail, 
corresponding with the upper flag measures of Yorkshire, and with 
them are two coarse grits, each about eighty feet thick. These re- 
pose upon a series of flags,t and the whole with their shales are based 
on the millstone grit. The remains of plants seem to be irregularly 
distributed ; Neuropteris cordata has only been found at the top. In 
some instances seams of coal appear characterized by an unusual pre- 
valence of plants, but are liable to much variation, Mr. Williamson has 
found remains of fish in connection with most of the coals from the upper- 
most limestone to the lowest coal in the ‘mountain mine.’ They chiefly 
consist of teeth of Diplodus gibbosus ; scales and teeth of Megalichthys 
Holopticus, two or three species ; Palgoniscus and allied genera, three 
or four species ; Coprolites, teeth and scales of singular forms and uncer- 
tain affinities. Unionid@ are generally diffused; but above the flag-series 
is a seam, three inches thick, entirely composed of individuals of a large 
species; and immediately above the mountain mine, is found Goniatites 
Listeri and Looneyi in large nodules, together with Pecten papyraceus. 
Mr. Williamson also exhibited several smaller sections, showing the varia- 
tions of the strata at similar heights above the same coal, and the im- 
possibility therefore of judging from mere isolated sections. The gene- 
ral resemblance, however, seems to show, that the various coal deposits 
are parts of one series, pushed up by the protrusion of the millstone 
grits. 
On the Dislocations of the Coal Strata in Wigan and the Vicinity. 
By Witttam PEACE. 
The district surrounding Wigan is intersected by a great number 
of faults or dislocations running nearly in straight lines, as shown on 
a map produced by the author. These faults, which run nearly pa- 
rallel to the magnetic meridian, and varying only about 10 degrees 
from it to the westward, dislocate the strata to a much greater ex- 
* Near Manchester. + The Haslingden flags. 
