MICHIGAN ACADEMY OF SCIENCE. 35 



The lowering- of tliis eastAvard dir^cliarge was not at first sufficient 

 to uncover Niagara Kiver, but eventually the ice border shrank within 

 the Ontario basin sutliciently to allow discharge over a low" col at 

 Rome, New York, the lake was drawn down to a level more than 150 feet 

 below that of the crest of Niagara Falls, and the cataract came into 

 operation. 



Lale Eric. Inasmuch as the eastern part of the Erie basin has suffered 

 considerable differential uplift subsequent to the draining of Lake 

 AVarren, the beginning of Lake Erie was as a small body of water in 

 the eastern end of its basin, which has been extended westward with the 

 raising of the outlet (Fig. 7). Evidence that it did not formerly cover 

 the western part of its area is found in the submerged lower courses of 

 the streams in the western part of the basin-, especially that of San- 

 dusky River, Avhicli has been traced by ]Mosely entirely across the bed 

 of Sandusky l^ay. Evidence of a rise of Avater is also found in sub- 

 merged stalactites in the caves on Put in Ray Island in the Avestern part 

 of the lake. 



ONTARIO BASIN. 



Laic Iroquois. The lake in the Ontario basin knoAvn as Lake Iro- 

 quois (Fig. 7) began as a narroAv strip of Avater along the front of the 

 ice at the south side of the Ontario basin and became gradually ex- 

 panded over the entire Avidth of the basin as the ice slieet melted back. 

 The discharge Avas continued through the MohaAvk A-alley during this re- 

 cession for the ice slieet completely blocked any passage doAvn the St. 

 LaAvrence. The level of Lake Iroquois Avas, throughout, considerably 

 higher than the present surface of Lake Ontario. Its beaches have 

 suffei'ed differential uplift and are much higher in the northeastern 

 portion of its basin than in the southAAestern. Inasmuch as the outlet 

 is at the side of the basin, the effect of the uj)lift has been to raise the 

 Avaters on the portion of the shore south of an isobase running through 

 the outlet and to cause the Avater to recede from the jiortion of the 

 shore north of the isobase. The highest beaches of the northern part 

 of the basin can not be traced into the southern part of the basin 

 for the rise of Avater in that part of the basin has effaced them almost 

 completely. The single beach present in the southern part of the basin 

 is, therefore, a correlatiAe or continuation of the loAvest Iroquois beach 

 of the northern part of the basin. 



Cha II) plain Hea. When the ice had opened a passage northeast of the 

 Ontario basin the altitude Avas so Ioav that the sea came into the basin 

 (Fig. 8) and stood at a level slightly higher in the northeastern portion 

 of the basin than the present shore of Lake Ontario, but in the remainder 

 of the basin the old sea level shore passes beneath the Avaters of Lake 

 Ontario. The differential ujjlift subsequent to this invasion of the sea 

 has giA'en Lake Ontario its present extent and level. 



LAKE ALGONQUIN. 



,The lake history thus far has required a separate discussion for 

 each of the lake basins but it is noAv possible to consider a lake stage 

 that involves the basins of the three ui)per lakes, Superior, Michigan, 

 and Huron, for upon the extinction of Lake Warren and the withdrawal 



