FORMER HIGHER LEVEL OF THE GREAT LAKES. 243 



I have said the Niagara River commenced its present 

 gorge during the Champlain Epoch. In reality there was 

 no Niagara River when this work commenced. Lake Erie 

 stretched down the valley of the existing river, and the 

 overflow of its basin wore the notch in the rocky rim 

 which was the beginning of the Niagara River. 



Lake Erie stands at present three hundred and thirty- 

 four feet above Lake Ontario. At the time of which I am 

 speaking it stood three hundred and seventy-two feet above 

 Lake Ontario, and filled the valley of Niagara River as far 

 as the heights above Lewiston (Fig. 84).* Indeed, there 

 are clear evidences, in the form of beaches containing fresh- 

 water shells, that the level of the river was once forty feet 

 above the present summit of the falls. No barrier has ever 

 existed to dam the water to this height except the escarp- 

 ment at Lewiston. This is one hundred and five feet above 

 the summit of the falls, and thirty-eight feet above Lake 

 Erie. The indications seem to be conclusive that the 

 waters of Lake Erie stood thirty-eight feet higher than at 

 present, and poured over the bluff at Lewiston, in a series 

 of cascades, three hundred and seventy-two feet, to the sea, 

 which at this time filled the basin of Lake Ontario. Dur- 

 ing the subsequent ages, the mighty stream has dug a 

 gorge in the solid rock, which is seven miles long, two hun- 

 dred and fifty feet deep, and, on an average, about one thou- 

 sand feet wide. The material transported from this gorge 

 into Lake Ontario is over three hundred and forty millions 



* Explanation of Fig. 84. — The diagram on the following page is in- 

 tended to illustrate the geological position of Niagara River and Falls, and 

 the ancient lake levels from Lake Ontario to Chicago. The vertical scale 

 is 560 feet to the inch ; the horizontal scale is irregular.. The diagram is 

 merely a series of sections around the lakes, placed end to end. The dips 

 of the strata are much exaggerated. The two portions of the diagram 

 join each other along the line a, b, c, d, etc. The figures against the ver- 

 tical dotted lines show the heights in feet above the sea of the points to 

 which the lines extend. 



