﻿S. V. Wood,jim. — American and British Surface- Geologij. 537 



(such, I suppose, as that wbicli blocked out the sea from the lake- 

 basin during the depression which gave rise to the marine clays of 

 the Lower St. Lawrence), or by the cutting away of barriers of 

 drift, or even, he adds, by the " warping of the earth's crust." It 

 does not appear that auy of these terraces, though possessing great 

 constancy of level, present such visible regularity as the well-known 

 roads of Glenroy ; but if, as is the more probable, the shrinkage of 

 the lake-basin was due to the removal of an ice-dam, their origin 

 would seem to be identical with that to which the inclination of 

 modern opinion refers these roads. 



A very interesting feature in the geology of the lake region 

 consists in the buried channels now filled with and concealed by 

 Drift. Some of these form the waste weirs just referred to. but 

 they occur also at various lower levels, even to levels beneath those 

 of the existing lakes ; so that if opened again great modifications 

 would take place in the hydrographical conditions of the St. Law- 

 rence basin ; and indeed Prof. Newberry ventures to assert that 

 buried channels of communication exist between Lake Erie and 

 Lake Ontario. If such exist, then, of course, Niagara could by 

 their opening be laid dry, and he dwells on the practical service to 

 which the various buried channels might be turned for engineering 

 purposes. He also insists on the soundness of the rock-basin 

 erosion theory as applied to the entire valley of the St. Lawrence. 

 This valley he describes as having been prior to the Glacial period, 

 and when the elevation of that part of the North American con- 

 tinent was considerably greater than now, the valley of a river- 

 system which flowed at much lower levels than at present ; and 

 which, instead of reaching the Atlantic as it now does by way of 

 the Gulf of St. Lawrence, flowed between the Adirondack and 

 Appalachian mountains, in the line of one of these buried channels, 

 passing through the trough of the Hudson Eiver, and emptying 

 into the Atlantic about eighty miles south-east of New York. At 

 this time, according to the Professor, that part of the St. Lawrence 

 valley which is now formed by the ba'=iius of Lakes Michigan and 

 Superior formed no part of the river-system to which they now 

 belong, but part of a separate river-system emptying itself into the 

 Mississippi, the Straits of Mackinau not being then opened ; and it 

 is to the erosive action of the glacier-ice, which during the Glacial 

 period crept down from the Laurentian highlands of Canada, and 

 filled these pre-existing valley systems, that he attributes their 

 excavation and conversion into the one great basin which now 

 receives so large a part of the drainage of North America, and is 

 referred to under the name of the lake-basin, or basin of the St. 

 Lawrence. 



Assuming that my suggestions as to the period and mode of 

 origin of the Ohio Eskers have some good foundation, I propose, 

 subject to the qualifying observations applied to each case, to 

 suggest certain synchronisms between the Glacial and post-Glacial 

 phenomena of the St. Lawrence basin and those of Britain, according 

 to the view of the English beds to which their study has led me. 



