3 557° 
the uppermost strata of the coarse underlying conglomerate. ‘The 
southern wall of an excavation from which the coal had been re- 
moved, and which wall occupied the place of the underclay, pre- 
sented impressions of the stems and leaves of Stigmaria; and on 
the more solid and slaty beds of the opposite wall, or original roof, 
there were leaves of Pecopteris, reed-like impressions, and Calamites. 
In the slightly inclined northern continuation of the coal-measures, 
Mr. Lyell observed in the Peachmount vein, three miles north-east 
of Pottsville, a bed of anthracite eight feet thick, overlaid by the 
usual roof of grey grit, and underlaid by blue clay or shale with 
Stigmariz. Impressions of ferns were likewise noticed in the coal 
itself. Only one instance was met with in the Pottsville coal-district, 
_by Mr. Lyell and Prof. Rogers, of a Stigmaria, placed at right angles 
to the plane of stratification. 
The Pottsville, or southern anthracitic coal-field of Pennsylvania 
was illustrated by a section resulting from the former labours of 
Prof. Rogers, under whose guidance Mr. Lyell examined the coun- 
try. ‘The following’ remarks may explain the general structure of 
the country ; the names applied to the formations are not, however, 
those previously employed by the American geologists, but those 
suggested by Mr. Lyell, in conformity with the conclusions at which 
he arrived after his tour in New York, and a comparison of the strata of 
that state with their British equivalents. ‘The contrast between the 
relative importance of most of the Silurian and Devonian groups in 
Pennsylvania and in New York, Mr. Lyell states, is very great, arising 
from a larger portion of sandstones and grits in the Pennsylvanian 
rocks. The section extends from north of Pottsville to the country 
ranging immediately south of Orwigsburg. To the south of the 
vertical coal-measures and the subjacent conglomerate there are 
displayed successively—tIst, a vast series, composed of red shales 
3000 feet thick, of grey sandstone 2400 feet thick, and of red sand- 
stone 6000 feet thick, the whole being considered by Mr. Lyell as 
portions of the old red sandstone ; and 2nd, of olive-coloured shale 
containing Devonian fossils. The dip of the strata is either nearly 
vertical or inverted. Still further south, and a short distance north 
of Orwigsburg, the olive-coloured shales are succeeded by very highly 
inclined or inverted beds of upper Silurian rocks flanking a protruded 
band of lower Silurian strata; and lastly, on the southern confines 
of the section is a trough of the Devonian olive-coloured shales 
resting on the upper Silurian strata. 
Beautiful exhibitions of the underclay with its associated plant, 
and of the overlying roof with its distinct remains, were observed by 
Mr. Lyell and Prof. Rogers at Tamaqua, in the southern coal-field. 
The thinning out of the grits and conglomerates of the west causes 
the beds of anthracite to be brought more nearly together in this 
district; and Mr. Lyell says, the decrease in the thickness of the in- 
tervening strata prepares the observer for the union of several of the 
seams still farther east, and for the enormous thickness of the anthra- 
cite at various places near the village of Mauch Chunk, or Bear 
Mount, particularly at the well-known Lehigh-Summit Mines. At 
