The coal measures or carboniferous formation is divided in two series of lower
and upper, by some 500 feet of barren measures, in Washington and Greene coun-
ties and the central hills of the Pottsville anthracite basin. The total thickness
of the carboniferous strata is unknown, and it is equally uncertain whether or
not if the Permian formation had ever been deposited upon them. Wliat is now
remaining will measure 3,000 feet. The bituminous and semi-bituminous beds
are the same at Ciunberland, Broad Top, Blossburg and Towanda, and are the
same beds as the anthracite beds in Luzerne, Carbon, Schuylkill, Columbia,
Northumberland and Dauphin. The character of the different coal may be traced
to the facility of the escape of the volatile hydrocarbon ous form of the coal beds
by the disturbed condition of the stratas. Where the gas is pent up the coal re-
tains its bitumen quality ; this being the case it renders it very remarkable.
Near Mauch Chunk the coal contains from 2 to 5 per cent, of gas ; at Potts-
town from 7 to 10 per cent. ; Lykens Valley, Shamokin and Trevorton from 10 to
12 per cent. ; on Broad Top from 16 to 17 per cent. ; at Altoona 20 per cent. ; at
Mount Pleasant and Clearfield 22 to 25 per cent.; and further west, from 30 to 40
per cent. In the anthracite regions many of the coal seams stand nearly vertical
and often the texture of the coal appears to be crushed. In the Allegheny and
Monongahela districts the coal seams are found in a horizontal position, while in
the antfiracite regions the seams are found jammed, broken, contorted, overlap-
I}ed, swelled, thinned, &c., forming numerous basins pointing east and west.
