No. 50.] 
397 
The high banks on either side of the river valley expose the outcrop- 
ping edges of the strata, and numerous small quarries are opened for 
the extraction of the thin layers of sandstone every where interstratifi- 
ed with, the shale. The hills are capped by thin layers of sandstone, 
with less shale than below, reddish or brownish in color, with abun- 
dance of scales of mica. These upper portions, so far as observed, are 
less distinctly characterized by fossils. 
The rocks, at the south line of the State and near the river level, con- 
sist of hard thick strata of grey sandstone, a part containing abund- 
ance of Leptffina and Delthyris, and succeeded by a thick concretiona- 
ry mass. The grey sandstone forms a fine material for building, and 
more durable than any other in this part of the country. Farther west 
and a little south of the county line, a thick mass of concretionary 
sandstone, with regular strata of grey sandstone is seen in the north 
bank of the Cowanisque creek. 
In order to give any definite information regarding the connexion of 
these rocks with those of known character above, I have found it ne- 
cessary to extend my examinations as far as Tioga, Pa. seven or eight 
miles south of the State line. At this place the upper member of the fos- 
siliferous group of New-York passes beneath the Old Red Sandstone, 
dipping south at an angle of from 6° to 8°. The Old Red Sandstone, 
which I shall have occasion to refer to in the description of other coun- 
ties, is at this place about 400 feet thick, brick red in color, with beds 
of softer or shaly rock of the same color, and contains fucoids and 
bones of fishes. 
The Old Red Sandstone approaches the south line of the county to- 
wards its western limits ; and may possibly extend within on some of 
the highest hills. 
In a section made from Dansville south through the valley to the 
Canisteo, and thence along Bennett's and Troup's creek to the south 
line of the State, nearly the same kind of rocks prevail in the same 
order of succession ; also in the valley from Patchins to Loon lake and 
Howard. 
The valley of Loon lake has already been mentioned as the con- 
tinuation of the Hemlock lake and Springwater valleys. In the neigh- 
borhood of the lake, large accumulations of alluvium rise in round- 
ed hills 50 or 60 feet above the general level, and skirt the valley on 
either side ; while beyond, the hills containing the rocks rise to a much 
