THE GEOLOGICAL HISTORY OF NEW YORK STATE IO. 
Iroquois. We know that the old Trent river channel is now higher 
than the Detroit outlet, but some of the proofs for the existence 
of the Trent outlet are as follows: the presence there of a large, 
distinct river channel; the convergence of the beaches toward that 
channel; and the fact that the land was then considerably lower on 
the north or northeast side of Lakes Ontario and Erie than on the 
south side. For example, in following the old Iroquois beach we 
find that it now gradually rises to higher levels until, even at 
Watertown, it is several hundred feet higher than near the mouth 
of the Niagara river. This tilting of the beach has been due to 
raising of the land since the lake existed, and it is evident therefore 
that during the Algonquin-Iroquois stage the Trent river channel 
was lower than that past Detroit. During this Lake Iroquois stage 
the waters of all the Great Lakes region discharged through the 
Mohawk-Hudson valleys, and the volume of water which flowed 
past Rome, Utica, and across the preglacial divide at Little Falls 
must have been as great, if not greater, than that which now goes 
over Niagara Falls. Much of the gorge cutting at Little Falls was 
accomplished by this great volume of water. The St Lawrence 
valley was still buried under the ice. 
Still later the ice withdrew enough to allow the Algonquin- 
Iroquois waters to discharge along the northern base of the Adi- 
rondacks and into what appears to have been ice-ponded waters in 
the Champlain basin, and thence southward into the Hudson ellie: 
The Mohawk river outlet was thus abandoned. 
Finally the ice retreated far enough to free the St Lawrence 
valley when the waters of the Great Lakes region dropped to a still 
lower level, bringing about the Nipissing Great Lakes stage (see 
figure 34). The Nipissing lakes found a low outlet through the 
Ottawa river (then free from ice) and into the Champlain arm of 
the sea. Postglacial warping of the land brought the Great Lakes 
region into the present condition, but this, and the Champlain sub- 
sidence, being really postglacial features will be described toward 
the end of the chapter. 
Other existing lakes and their origin. Counting all, from the 
smallest to the largest, there are within the borders of New York 
State thousands of lakes, which constitute one of the most striking 
differences between the geography of the present and that of pre- 
glacial time. These lakes are widely scattered over the State though 
there are three general regions worthy of particular mention as 
follows: the Finger lakes region of western New York; the Adi- 
rondack mountains; and the southeastern portion of the State. 
