﻿140 NEW YORK STATE MUSEUM 



From the Iroquois to the Gilbert levels the waters fell with 

 comparative rapidity by the removal of the ice dam. The apparent 

 lowering of the Gilbert waters was on the contrary by the very 

 slow uplifting of the land out of the sea-level waters. This rising 

 of the land must have been so slow as to give opportunity to the 

 waves at all minor levels to produce shore line phenomena, and 

 many such are found. However, such proofs of the presence of 

 standing waters are missing over long stretches of even the summit 

 plane, which emphasizes the well recognized fact that absence of 

 clear wave work does not necessarily prove the absence of standing 

 waters. 



But while beach phenomena may be lacking or weak over wide 

 stretches we find other evidences of the waters. Either by- the 

 lowering of the Iroquois waters over the higher ground or by the 

 lifting of the lower ground through the Gilbert waters all the 

 land surfaces have been brought into the zone of wave action and 

 subjected to erosion or deposition by the agitated waters. In 

 consequence the steep slopes, the projecting rock masses, tables 

 and knobs, have been more or less cleared of their drift and 

 specially of the finer material, which has been shifted to lower 

 levels. The broader plateaus and plains have been smoothed 

 and the lower grounds, valleys, basins and hollows, have been 

 more or less filled or silted with the detritus, sand or clay, washed 

 from the higher ground. This action explains two striking 

 characters of the region, the areas of bare rocks and the silt- 

 filled basins, which will be discussed later. 



Conclusive proof that the lower waters were confluent with 

 the sea would be the finding of marine fossils. Such have not 

 yet been found in the Ontario basin, though they are abundant 

 in the Champlain and St Lawrence valleys, and marine shells 

 have been found as far west as Ogdensburg. 



Atmospheric erosion. The whole region, above the Ontario 

 level, has long been subjected to a renewal of the atmospheric 

 agencies. The length of time is unknown, but is not equal for all 

 the area. For the lower plains, near the present lake, the time must 

 somewhat exceed the life of Ontario; while for the higher ground, 

 above the Gilbert levels, the time must cover not only the life of 

 Ontario but also that of Gilbert gulf. If we estimate the life of 

 each of these water bodies as 10,000 years it may give some fair 

 conception of the duration in years. For lands above the reach 

 of Lake Iroquois its length of life must be added to the time of 

 exposure, at least another 10,000 years. It is likely that these fig- 

 ures are too small rather than too large. 



