66 Geological Society: Mr. Logan on the 
the first ten being sunk in sand and the debris of pumice; and the 
remainder in pumice and scoriz intermixed with obsidian. At the 
depth at which water was obtained the pumice assumed a more 
compact structure. 
March 23, 1842.—A paper was first read, “On theCoal-fields of 
Pennsylvania and Nova Scotia,” by William Edmond Logan, Esq., 
F.G.S. 
The objects of this paper are to give, 1st, a few particulars con- 
nected with the extent and character of the carboniferous deposits 
of Pennsylvania, and to point out the extension to the coal-fields of 
America of some facts bearing on the origin of coal, advanced by 
the author in a previous memoir on South Wales; and, 2ndly, to 
detail the results of his observations in Nova Scotia. 
1, Pennsylvania.—The whole of the Pennsylvanian coal-fields 
have been carefully examined, the author says, by the corps of 
State Geological Surveyors, under the able direction of Prof. Rogers, 
to whose admirable reports he bears testimony; but he Jaments 
their not being accompanied by a general map. In the construc- 
tion of a small plan to accompany his memoir, and compiled from 
different sources, the author says, he is solely indebted for the con- 
tour of the bituminous district to Mr. Leslie and Mr. McKinnaly, 
attached to the State Survey; and that in the delineation of the 
complicated anthracitic regions he has taken advantage of a manu- 
script map which he obtained from Mr, Fisher, a coal-surveyor of 
Pottsville. 
The Pennsylvanian carboniferous district is only a portion of that 
great coal region which extends into Maryland, Virginia and Ohic. 
The greatest breadth of the main coal-field of Pennsylvania is from 
the Alleghany mountains to within a dozen leagues of the southern 
shore of Lake Erie; and its length from Coudersport on the north 
to the southern angle of the State is about 200 miles. There are, 
however, also four or five important detached carboniferous regions 
on the Atlantic side of the Alleghanies, besides numerous small 
ones. The coal-measures consist of micaceous sandstones, arena- 
ceous, argillaceous and carbonaceous shales, and valuable bands of 
limestone. In the bituminous district, under 800 feet of unproduc- 
tive strata, are about 10seams of coal, having an aggregate thickness 
of 50 feet, the whole resting upon a hard, coarse conglomerate, which 
is from 800 to 1200 feet thick at its south-eastern development, but 
is considerably thinner to the north-west. Beneath the conglome- 
rate is a deposit of red shale which varies in thickness from 3000 
to less than 100 feet, and disappears, it is believed, to the south- 
west. The next formation in descending order, with the exception 
of an interposed bed of fossiliferous limestone, consists of massive 
sandstones, conglomerates and shales, and it possesses a more uni- 
form thickness than the two next superior deposits. All these for- 
mations are considered by Prof. Rogers to constitute a carboniferous 
system, though no profitable coal exists below the uppermost de- 
posit; the remains of plants however occur throughout, and one or 
more seams of coal about a foot thick exist in the red shales. This 
