200 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



Recent investigations 'by Gilbert, Spencer, Taylor, and others have 

 brought to light evidence that earth movements have produced marked 

 changes in the drainage of the Great Lakes and their expanded prede- 

 cessors. Because of northward differential uplift the drainage of the three 

 upper lakes (Superior, Michigan, and Huron) has been thrown into a course 

 farther south than it formerly took, the old course being eastward from 

 Georgian Bay to the Ottawa River instead of past Niagara Falls. The 

 limits of change may not yet have been reached, for the movement appears 

 to still be in progress, and if it continues to the amount of only a few feet 

 the discharge of the upper lakes will be diverted from Niagara to Chicago, 

 and they will then be connected with the Mississippi instead of the St. 

 Lawrence system. Changes of this class and magnitude illustrate the great 

 influence which earth movements may have upon drainage under favorable , 

 conditions. On the other hand, very great earth movements have taken 

 place in some localities which apparently have had but little influence upon 

 the drainage. The Susquehanna River crosses the entire Appalachian sys- 

 tem, and yet seems to have maintained its course faithfully, notwithstanding 

 it was antagonized by the maximum flexure of the mountain system. The 

 Delaware, the Juniata, the Potomac, and even the upper waters of the 

 Kanawha furnish illustrations of similar persistence. 



From these illustrations it appears that the rate of movement must be 

 sufficiently slow for a stream to cut down its passage across the rising arch 

 if there is to be no diversion. It may also be inferred that a stream flowing 

 at a low gradient might be diverted, as well as a lake, by such a movement 

 as that which has produced the changes in the drainage of the Great Lakes. 

 Indeed, the South Fork of Chicago River will be changed to a lake and 

 finally made to reverse its present course if the chang-e in the discharg-e of 

 the Great Lakes from Niagara to Chicago is effected. 



SECTION II. ST. LAWRENCE SYSTEM. 



In the present discussion only that portion of the St. Lawrence system 

 is considered that lies within the territory covered by this report. It 

 includes the soutliern tributaries of Lake Ontario from the Genesee west- 

 ward to the Niagara River, Tonawanda Creek, an eastern tributary of 

 Niagara River, and the southern and western tributaries of Lake Erie in New 

 York, Pennsylvania, and Ohio. The discussion begins with the Genesee 

 River and proceeds westward to. the western end of the Lake Erie Basin. 



