352 
GEOLOGY OF THE FOURTH DISTRICT. 
Terraced Hills. 
169. 
Sketch of the hill on the west side of Seneca lake valley, at Jefferson. 
Besides the well-defined ridges, which can only have been made by the water of the lakes 
or ocean remaining at this elevation for a considerable length of time, we often find a series 
of terraces which appear to have been produced by the rapidly subsiding water. In the il¬ 
lustration above is presented a series of distinct terraces, the surface of each with a few large 
pebbles upon it. Those represented are exceedingly uniform, and below the lowest are several 
others less distinct. I had at first supposed them due to the alternating hard and soft layers 
of rock; but the surface is so deeply covered with drift as scarcely to allow any influence 
from the strata beneath, even if the alternations were as regular as here represented, which is 
not true. 
The sketch is of the hill at Jefferson, at the head of Seneca lake, taken from the opposite, 
more than a mile distant. When standing upon the hill sketched, and looking upon the opposite 
side of the valley, there appears a similar series of steps or terraces, though not so distinctly 
defined. Many similar appearances have been observed, but after the country becomes cul¬ 
tivated, they are soon obliterated. The ascent from Lake Erie in many places presents these 
terraces often well defined, and, by careful examination, they may afford some clue to its 
successive drainage previous to the period when the well-defined ridge before alluded to was 
formed. 
The contemplation of these monuments of the former elevation of the water, and the marks 
of its gradual subsidence, lead the mind back to periods when the conditions of the surface, 
and the proportions of land and water, were very different from the present. If the relative 
elevations of the surface in New-York have remained the same from that period to the present, 
then the greater portion of the middle and eastern parts of the State would have been covered 
with water. At the same period, there must have been a communication between the waters 
of this great valley and the Mississippi, and with the ocean through both that valley and the 
