ere) NEW YORK STATE MUSEUM 
By successive stages, due to a complete removal of ice from 
central New York and a draining of the glacial lake in the Mo- 
hawk valley, the waters dropped to below Warren level until Lake 
Iroquois was formed (see figure 33). The old beach line of this 
lake is still plainly visible in New York and with some slight inter- 
ruptions has been traced from near the mouth of Niagara river to 
just north of Rochester, past Syracuse, along the south, east, and 
north sides of Oneida lake, and thence along the western base of 
the Tug Hill plateau to near Watertown. The well-known ridge 
road between Niagara river and Rochester is built on the old 
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Fic. 33 The Algonquin-Iroquois stage of Great Lakes history when the 
ice had retreated far enough to open the outlet through the Mohawk valley. 
After Taylor 
Iroquois beach deposit. Lake Iroquois covered somewhat more 
than the present area of Lake Ontario, and the distinctly lower 
water level here than in the Erie basin allowed the modern Niagara 
river to begin its history by flowing northward over the limestone 
plain near Buffalo. Meantime the waters of the upper lake basins 
had merged to form Lake Algonquin which at first probably dis- 
charged past Detroit through the Erie basin and into Lake Iroquois 
by way of Niagara river. Later, however, when the ice had with- 
drawn a little farther northward, a lower outlet was opened through 
the Trent river’ by which Lake Algonquin drained into Lake 
