l899-] FAIRCITILD PREDECESSORS OF NIAGARA. 275 



The glacier occupied the Laurentian basin and all its present low 

 northward and eastward passes, and consequently all the waters were 

 forced across the divide to the southward. When the west end of the 

 Superior basin was uncovered, it held a glacial lake, which we call 

 Lake Duluth. In the same way a local glacial lake was formed in the 

 southern end of the Michigan basin, known as Lake Chicago, and in 

 the western end of Erie basin, called Lake Maumee. The lowest of 

 the three outlets of these lakes was that of Lake Chicago, which 

 formed the channel now utilized by the Chicago drainage canal. 

 Eventually, by the continued recession of the ice front, land was 

 uncovered either side of the Michigan valley, lower than the St Croix 

 outlet of Lake Duluth or the Fort Wayne outlet of Lake Maumee, 

 and the Chicago outlet robbed the two higher outlets. 



The high glacial waters of the Erie basin were finally extended 

 north and east by the continued recession of the ice dam, until they 

 covered all of the Erie basin, the lower Huron basin and the south- 

 western part of the Ontario basin. These waters are called Lake 

 Warren. At this time the ice front lay against the high ground south- 

 ward from Syracuse, and therefore blocked the waters from the low 

 pass at Rome to the Mohawk valley, which was lower in altitude than 

 the Michigan outlet of Lake Warren waters. 



As the ice front weakened and receded in the Syracuse region, 

 the Warren waters, which formed in New York a belt several miles in 

 width along the ice border, and reaching southward up the valleys of 

 the present " finger " lakes, crept eastward at their proper level. 



One summer day, the critical moment came, and the high water 

 found escape eastward past the ice to the open Mohawk-Hudson. At 

 first this may have been an insignificant spilling, but the flow increased, 

 and with the downcutting of the waste-weir an irresistible flow was 

 established. The first spillway we cannot precisely locate, but it is 

 probably one of two east-and-west gorges in rock, one being two miles 

 east of Jamesville, the other two miles southwest. 



With the farther retreat of the ice front, other lower canyons were 

 cut, and a series of great rock gorges were made leading across the 

 ridges that separated the north and south valleys in which the glacial 

 waters were ponded at their successive levels. The most western of 

 the canyons heads on the Onondaga limestone, about four miles north 

 by east of Skaneateles and conveyed the flood of hypo- Warren waters 

 eastward to the Otisco valley, building a huge delta south of Marcellus 

 village. 



