68 Geological Society: Mr. Logan on the 
side of the Alleghanies and eastward of the Susquehanna river pro- 
duce anthracite, and it was to them that Mr. Logan more particu- 
larly directed his attention. These detached fields consist of a num- 
ber of long, narrow, irregular troughs, separated by anticlinal axes 
of the quartzose conglomerate or subjacent red shale, and they are 
distinguished by the names of the southern, middle and northern 
anthracitic coal regions. 
The southern region extends from Mauch Chunk on the Lehigh 
river nearly to Petersburgh on the Susquehanna, a distance of 70 
miles, but its greatest breadth does not exceed six. It is traversed 
by five anticlinal axes parallel to one another and to that which 
bounds the trough, the steeper escarpment being on the north side; 
and the angle increases with each successive ridge, so that at the 
southern the strata have been elevated beyond the perpendicular 
and turned over, exposing beds many thousand feet below the coal- 
measures. Pottsville and Mount Carbon are mentioned as points 
where these phenomena are well exhibited. On inspecting the 
coal-seams in this neighbourhood, Mr. Logan observed, associated 
with every one he examined, similar stigmaria beds to those which 
he had previously described in his paper on South Wales; and 
he was enabled by them to detect the inverted position of the strata. 
The undulations in this coal-field render an estimate of the number 
of seams difficult, and Mr. Logan thinks that the 70 or 80 reported 
by the miners to exist, ought to be reduced to one-fifth. Some of 
the seams are of great dimensions, particularly that at the Room- 
Run and Summit mines near Mauch Chunk. The thickness of 
this deposit, with its associated partings of carbonaceous shale and 
an interposed stigmaria bed, is 50 feet, and it is estimated that the 
seam must yield from 40,000 to 50,000 tons per acre. At the 
Summit mines the coal is quarried to open day. Beneath the entire 
mass is a thick bed of underclay filled with Stigmariz, and the oc- 
currence of a similar bed 7 or § feet above the bottom of the coal, 
supports, Mr. Logan says, the opinion of Prof. Rogers and the 
miners, that the deposit in its progress westward splits into more 
than one workable seam. 
The middle anthracitic coal region consists of an aggregate of 
narrow troughs, also separated by ten parallel anticlinal ridges or 
« geological wrinkles ;” and the troughs are divisible into the west- 
ern and eastern groups. The former, having an area of forty-five 
miles by five, comprises the Shamokin and Mahony coal-fields, as 
well as the basin of Sheenandoah valley, with several small districts ; 
and the eastern group, with an area of twenty miles by five, con- 
sists of the coal-basins of Beaver Meadow, Duck Creek, Hazle 
Valley, Black Creek, Bucks Mountain, and McCauley’s Mountain. 
From the frequency with which the conglomerate is brought to the 
surface, Mr. Logan says, it may be inferred that the middle region 
is shallower than the southern. 
The northern anthracitic region, bounded like the others by the 
quartzose conglomerate, is crescent-shaped, and includes the beau- 
tiful valley of Wyoming. Its length, from Carbondale to Knob 
