188 THE CANADIAN NATURALIST. [Tol. viii. 



writer has not met with any connected or detailed investigation 

 into the physical cause of the basins in which they lie, and which 

 determine their existence. Until lately no proposition at all 

 tenable had been promulgated ; but since Professor A. Ramsay's 

 strong advocacy of a glacial origin for the basins of certain Euro- 

 pean lakes, there seems to have been a tacit extension of this 

 theory, so that according to some it explains the formation of 

 almost all lakes in the North Temperate Zone, and were it not 

 for the existence of several great inland seas in Equatorial 

 Africa, it would, we think, be accepted by not a few as the sole 

 and sufficient cause of all lake basins on the surface of the globe. 

 The merits of this theory we do not propose now to examine. 

 Our purpose is merely to test its application to the case of the 

 great North American lakes. The publications of the Geologi- 

 cal Survey of Ohio have shown that opinion is yet divided upon 

 this point. Dr. Newberry, its director, is apparently himself in 

 doubt, as we infer from expressions in different parts of the work. 

 For instance, we read in the volume for 18G9, p. 28 : 



" Lake Erie in the glacial era was not a lake but an excavated 

 valley into which the streams of Northern Ohio flowed." 

 But in the volume for 1873, Dr. Newberry says: 

 "It is doubtless known to some who may be readers of this 

 volume, but probably is realized by few, that the basin of Lake 

 Erie in all its length and breadth — as well as the smaller and 

 yet deeper one of Lake Ontario, and the broader and far deeper 

 ones of Lakes Michigan and Huron — has been excavated by 

 mechanical force from the solid rock. . . . They are plainly 

 basins of excavation dug out of sheets of rock which were con- 

 tinuous over all the area they occupy. . . . Any one who will 

 stand on the cliffs which overlook the lake in North Eastern 

 Ohio, 750 feet above the water, and will look over the sea-like 

 expanse toward the Canadian shore, will get some realizing sense 

 of the vastness of the mechanical effect which has been produced 

 here. . . . The agents were unquestionably the same that have 

 produced all the great monuments of erosion seen elsewhere — 

 water and ice; and of the two that which was by far the most 

 potent and that which alone could excavate broad boat-like 

 basins such as these was Ice." p. 49. 



Again we read in the volume for 1874, p. 77 : 

 " Previously to the glacial period the elevation of this portion 

 of the continent was considerably greater than now, and it was 



