GENESEE DRAINAGE BASIN. 205 



toward the northern end of the drainag-e basin one can recognize several 

 water plains, each of which is in harmony with an oiitlet. The following 

 summary of these stages is given by Fairchild: 



The first stage in the glacial drainage of the valley was from the headwaters to 

 both the Susquehanna and the Ohio-Mississippi, with altitudes of water surfaces over 

 2,200 feet. 



The second, third, and fourth stages drained to the Ohio-Mississippi, with 

 altitudes respectively 2,068, 1,600, and 1,496 feet. 



The fifth and sixth stages drained to the Susquehanna, with altitudes of 1,320 

 and 1,210 feet. 



The seventh and eighth stages drained to the Illinois-Mississippi, with altitudes 

 from 1,200 down to 880 feet. 



The ninth stage drained to the Hudson, with an altitude of 436 to 440 feet.^ 



The tenth stage is the nonglacial St. Lawrence drainage, with present 

 altitude of 247 feet. 



The several outlets utilized by these lakes show marked differences in 

 the amount of cutting, suggesting great differences in the duration of the 

 lake levels. The first outlet that shows evidence of long operation is the 

 one at 1,600 feet, which discharged westward through Honeoye and Oswayo 

 creeks to the Allegheny River. The amount of downcutting here, as esti- 

 mated by a delta at the mouth of a gully at the east border of the col, is 60 

 to 70 feet, and the width of the rock gorge 1,000 feet. The excavation is 

 in soft shales. The next lower outlet, 1,496 feet, which leads past Cuba, 

 seems to have encountered no rock, but simjaly leveled the drift filling at 

 the summit, the channel being spacious and near to grade.- In the next 

 stage the waters in the Grenesee Valley apparently dropped to about 1,320 

 feet and discharged through a channel at the head of Canaseraga Creek 

 into Dansville Lake, and thence by a channel past Burns to the Chemung- 

 Susquehanna. But in course of the retreat of the ice sheet a passage was 

 opened to Dansville Lake at a level suiiiciently low to cause the Genesee 

 Lake to drop to the level of the outlet past Burns, 1,210 feet. This outlet 

 is reported by Fairchild to be the grandest of the abandoned water courses. 

 Its width is about three-fourths of a mile and its length 12 miles. It has a fall 

 of but 10 feet in the first 6 miles and of but 40 feet in the second. Flood 

 plains are seen all the way from Burns to Hornellsville at a height of 16 to 

 30 feet over the channel. It is thought that the effective life may have been 



' Since writing the above Professor Fairchild has recognized a stage of eastward discharge higher 

 than this, which is marked by the Geneva Beach and which he calls the Lake Dana stage. The Geneva 

 beach: Bull. Geol. See. America, Vol. VIII, 1897, pp. 281-284; Lake Dana: Vol. X, pp. 56-57. 



