310 
BITUMINOUS COAL. 
THE BITUMINOUS COAL-FIELDS OP PENNSYLVANIA. 
Great and valuable as are the anthracite deposites 
of Pennsylvania, her bituminous coal-region is still 
more extensive and inexhaustible. We have al- 
ready stated that the great secondary deposite, which 
extends from the Hudson to the Mississippi, and prob- 
ably to the Rocky Mountains, is in Pennsylvania 
limited by the Alleghany Mountains, which appear 
to form the barrier or dividing line between the an- 
thracite and bituminous coal-beds, or between the 
secondary and transition formations. The union or 
junction of these formations is distinctly marked in 
the end of the mountain where the west branch of 
the Susquehanna breaks through it, above Bald 
Eagle, the latter resting against the former, and 
forming the basin in which the bituminous coal, in 
regular and successive strata, is deposited. 
This coal-field, therefore, is confined to the west 
side of the Alleghany, and is supposed to extend to 
the centre of the mountain. In the southeast cor- 
ner of Somerset county, and in the western parts of 
Bedford and Huntingdon counties, this coal deposite 
would appear to extend to the southeast of what is 
there called the Alleghany, and occurs in great 
abundance on Will's Creek, Jennings Creek, &c., 
emptying into the Potomac. The bituminous coal- 
beds vary from one foot to 12 in thickness, but rare- 
ly exceed six feet. They lie in nearly horizontal 
strata, with about sufficient dip to free the mines from 
water ; some hills containing three and four beds, 
with alternate layers of earth and strata, resting 
between a firm, smooth slate roof and floor, as 
shown in the sections above given. Faults are sel- 
dom met with, as is the case in the anthracite strata, 
which goes to prove that all this vast extent of sec- 
ondary rocks was once the bottom of a great lake 
or sea, which has been drained by the waters of the 
Mississippi, the St, Lawrence, the Susquehanna, and 
