ioo The American Geologist. August. 1903. 
clearly the depression of the area between the Cincinnati anticline and 
the eastern shore of the Appalachian sea.* 
Hypsographic Changes. Xo important hypsographic chang- 
es occurred during the accumulation of the lower black shale, 
except the continuance of the subsidence previously noted, 
whereby room was provided for the incoming sediment, which, 
in Xew York, is 150 feet and, in Ohio, 300 feet in thickness. 
But in the succeeding subperiod — that of the middle beds 
or the so-called Erie shales, of Newberry — this subsidence 
became much more pronounced. The bottom of the gulf set- 
tled down over its whole area, so as to allow the accumulation 
of this enormous mass and in the east of its equivalent, the 
Portage and Chemung, with which there should be included 
the Catskill. These, in the central part of the basin, are not 
less than 3000 feet thick and imply slow subsidence by their 
many indications of shallow water. This huge mass, covering 
nearly 10,000 square miles of country, represents the erosive 
products of the latter part of the Devonian era. Its finer ma- 
terials are spread out over the western, southern and central 
districts and the coarser deposits chiefly characterize the east- 
ern region. 
So extensive a filling implies the erosion, and therefore the 
elevation, of an extensive land area elsewhere. All indications 
point to the northeast, and especially to Xew England, as the 
region where the uplift occurred. Obviously this is only a 
continuation of the change above described, whereby the north- 
eastern channel was closed in the Hamilton, or. more exactly, 
in the Marcellus sub-period. The limits of the area affected by 
this hypsographic movement it is not now possible to determine, 
but the bulk of the sediment is ample evidence that it was of 
no small extent. It probably affected, in part at least. New 
* The data for the sections given in the foregoing diagram can be found, as 
follows : 
Findlay Geo!, of Ohio, vol vi, p. . 
Fostoria " " vol. vi. p. 193. 
Tiffin " " vol. vi, p. 197. 
Plymouth " " vol. vi, p. 302. 
Berea " " vol. vi, p. 4-33. 
Akron E. W. Clavpole. 
Ravenna " 
Nelson I-edges 
Youngrstown ' Geol. of Ohio. vol. vi, p. 402. 
E. Liverpool " " vol. vi. p. 335. 
Crawford Co., Pa Genl. Survey of Fa.. Q4. p. 66. 
Watson Well. Pa " " " T 3 .p. 154, 
Cobham Well. Pa " " - ' U. p. 211. 
Dennis Well. Pa " " " K. p. 292. 
Potter Co., Pa " " " G 3 , p. 82. 
