24 
GEOLOGY OF THE THIRD DISTRICT. 
CHAPTER V. 
NEW-YORK SYSTEM ; 
WITH A DETAILED ACCOUNT OF THE ROCKS AND GROUPS TREATED, IN THE ORDER ENUME¬ 
RATED IN THE SECOND CHAPTER. 
Few countries, if there be even any, are so happily circumstanced as New-York, for the 
investigation of the rocks of the system which bears its name. The greater part of the Mis¬ 
sissippi valley, and more especially the east side, is composed of its rocks. These rocks 
extend thence through Ohio and Pennsylvania in a northeast direction, enter and cover the 
whole of the northwest half of New-York, and retain the same undisturbed and horizontal 
position, so characteristic of them in that valley. On the east side of the Mississippi, from 
Alabama to the northern part of Pennsylvania, no higher rocks are seen upon their surface 
than those of the Coal series ; and this series is found in the States of Tennessee, Virginia, 
Kentucky, Ohio and Pennsylvania, the series terminating in the latter State, but reappearing 
in the British possessions in a northeast direction. 
In the west, few or no profound excavations exist; and a considerable extent of country 
generally must be-travelled, in order to obtain knowledge of more than a few of them. In 
New-York it is widely different. By the same cause which excavated Lake Ontario, excava¬ 
tions at higher levels were made, disclosing the ends, or the outcrop of the rocks, giving rise 
to a succession of surfaces and cliffs, unparalleled in number, magnitude and range, extending 
from Niagara river in an east line, beyond the Hudson. The cliffs attain, in Herkimer and 
Otsego counties, the aggregate height of nearly one thousand five hundred feet, their rocks 
slightly inclining to the southwest. These are followed by others to the south, in regular 
succession, but no regularity of surface outline, the terminal one of the whole series being 
the rock upon which the coal of Pennsylvania is placed; the nearest locality of this fossil 
production, or its series, to the third distiict, being about twenty-five miles south of the line 
of the two States. 
These excavations east and west, by which the outcrop of the whole range of southwestern 
rocks of the Union were exposed, have been no less advantageous to the industry of the State 
than to the.geologist. They have given to New-York, in connecting the eastern with the 
western waters, a reduction of level fully equal to one thousand two hundred feet. 
