Review of History of the Great Lakes. — Spencer. 297 
square miles. But to the east it has not been defined, and its 
old margins have been very considerably tilted. With the 
continued rise of the land, the waters sunk to a lower level, 
dismembering Warren water and producing: — 
11. Algonquin ami Lundy Waters. When the level of the 
water fell about 150 feet below the level of the Forest beach, 
the upper three lakes were enclosed within the Algonquin 
beach, and Erie within the Lundy beach, which latter extend- 
ed to the Ontario basin, At that time the waters of the lakes 
did not reach to their western and southern boundaries of to- 
day. Toward the northeast they connected by straits with 
the waters in the Ontario basin, but their eastern limit has 
not been surveyed. 
I.J. Iroquois Water anil Birth of the Modern Lakes. The 
waters gradually subsided to 300 feet below the planes 
of the Algonquin and Lundy beaches when the Iroquois shore 
commenced to be formed. This level has been proved to have 
been that of the sea, although it is now 363 feet above tide, 
at the head of lake Ontario, 750 feet near the outlet of the 
lake, and nearly 1,500 feet at the northeastern extension of 
the Adirondacks. The old water plane is recognizable, by 
either continuous or interrupted portions of its shore line, all 
tlie way to the depression of lake Champlain, but it is not yet 
fully known, especially as to its location north of the Ottawa 
river. Lower beaches are also known in the Ontario basin. 
With the subsidence of the waters to the Iroquois level, the 
upper lakes shrunk within their narrow limits, and the Niag- 
ara river had its birth, at first draining only the Erie basin, 
whilst the three upper lakes outflowed by way of the Ottawa 
valley. Indeed, the Iroquois waters sunk more than 220 feet 
below the Iroquois beach, thus greatly reducing the area of 
that lake. The waters of the upper lakes also sunk so as to 
form sheets of very contracted proportions. By the continued 
rise of the land towards the northeast, the rims of the lakes 
were raised, backing the waters in the basins and extending 
the modern lakes as we see them. This rise was intermittent, 
but, for the average of the secular episodes of movement and 
repose, the warping in the Niagara district appears to have 
been a foot and a quarter in a century, and it was double that 
