310 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1912. 



combined in a complex series of changes leading finally to the later, 

 larger lakes that filled the whole basin of Lake Ontario. The suc- 

 cession of changes has been set forth in considerable detail by Fair- 

 child ^ and illustrated by a series of maps. The first local glacial lakes 

 had independent outlets toward the south. 



LAKE NEWBERRY. 



Following this the dozen or more small lakes in the "Finger lake" 

 valleys had merged into one lake, Lake Newberry, with its outlet 

 southward from Seneca Lake to the Susquehanna Kiver. 



LAKE HALL. 



At a slightly later stage of recession an outlet for these waters was 

 opened westward to the glacial waters in the Lake Erie basin initiating 

 Lake Hall. 



LAKE VANUXEM. 



At a stUl later stage an outlet was opened eastward to the Mohawk 

 Valley and Lake Vanuxem resulted. After this there was for a 

 time free drainage eastward with only two low, small lakes, one in 

 the Genesee Valley and one in the valley of Cayuga Lake. 



Following this stage the waters of the southern part of the Lake 

 Ontario watershed merged with the glacial waters in the Huron-Erie- 

 Ontario basin. They are discussed above under the heading "Glacial 

 lakes of the Huron-Erie-Ontario basin." 



LAKE DAWSON. 



When the waters had fallen so as to separate those in Lake Erie 

 from those of the Lake Ontario basin, the outlet was established 

 eastward past Syracuse, N. Y., and a number of oscillations of lake 

 level probably occurred corresponding to slight retreats and read- 

 vances of the ice front. These changes aftected the height and eroding 

 power of Niagara Falls. Toward the end of these oscillations the 

 relatively high ground east of Rochester became a barrier against 

 which the ice front rested, holding Lake Dawson in the Lake Ontario 

 basin west of Rochester, while a smaller lake into wliich it flowed 

 filled a narrow strip farther east and emptied into the Mohawk. 



LAKE IROQUOIS. 



Finally the waters of the Lake Ontario basin fell to the level of the 

 pass at Rome, N. Y., and discharged eastward through the Mohawk 

 Valley. (Fig. 6, ice border at position I.) Tliis established Lake 

 Iroquois, which endured for a relatively long time. The land, how- 

 ever, was strongly uphfted around the north side of this basin while 

 the lake was discharging at Rome. This backed the water up on 



1 Fairchild, H. L., Glacial waters in central New York, N. Y. State Education Department Bulletin, No. 

 442; N. Y. State Museum, Bull. No. 127, 1909. 



