Science, Geology and Physics 



(confining it to the basins of Superior, Michigan and Huron) !895 

 with an outlet by way of the Ottawa valley, and Lundy pencer 

 gulf (occupying the Erie basin and) extending into the Ontario 

 valley. These two bodies of water appear to have had a com- 

 mon level as if connected in some way across the Ontario basin, 

 but their northeastern extensions are not known and involve 

 unsettled questions that do not affect the history of Niagara. 

 Again, the waters were lowered so that the Niagara River 

 emptied the overflow of the Erie basin, without a fall into the 

 Ontario valley. This condition did not last long, for the waters 

 sank to a level (Iroquois beach) of 300 feet below the Lundy 

 (and also Algonquin) plain, and the falls commenced their 

 descent with the waters of the Erie basin alone. The subsidence 

 was accompanied by slight pauses, but waters remained for a 

 long time at the level of the Iroquois beach, which is now about 

 135 feet above Lake Ontario at the end of the gorge. Again 

 the waters subsided to the level about 80 feet beneath the present 

 level of the head of Lake Ontario, and thereby lengthened the 

 river to 1 2 miles beyond the end of the chasm. At this time the 

 descent of the river after passing the rapids at Johnson's ridge 

 was 420 feet. By the continued northeastern terrestrial elevation 

 the waters of the Huron basin were turned from the Ottawa 

 drainage into the Erie basin, whose northeastern rim was elevated 

 so as to flood the lake. Later, the waters at the head of Lake 

 Ontario were raised 80 feet to the present level. This differ- 

 ential movement was at zero at the head of Lake Erie; 2.5 feet 

 per mile in the Niagara district; 4 feet northeast of Lake Huron, 

 and 5 feet per mile at the outlet of Lake Ontario. 



At the nativity of the Niagara River there was no fall. A 

 little later in the Iroquois episode the falls were very much like 

 the modern American cataract, both in height and volume, but 

 afterwards it increased in magnitude and went through the 

 changes noted later. 



38 593 



