of the Canadian Lakes and Valley of the St. Lawrence. 185 



than modern beaches. Several ridges, east and west of Cleveland 

 in Ohio, on the southern shore of Lake Erie, were ascertained to 

 have precisely the same characters. Mr. Lyell compares them all 

 to the osars in Sweden, and conceives that, like them, they are not 

 simply beaches which have been entirely thrown up by the waves 

 above water, but that many of them have had their foundation in 

 banks or bars of sand, such as those observed by Capt. Grey running 

 parallel to the west coast of Australia, lat. 24° S., and by Mr. Dar- 

 win off Bahia Blanca and Pernambuco in Brazil, and by Mr. Whit- 

 tlesey near Cleveland in Lake Erie. They are supposed to have been 

 formed and upraised in succession, and to have become beaches as 

 they emerged, and sometimes cliffs undermined by the waves. The 

 transverse and oblique ramifications of some ridges are referred to the 

 meeting of different currents and do not resemble simple beaches. 



The base-lines of the ridges east and west of Cleveland, are not 

 strictly horizontal according to Mr. Whittlesey, but inclined five 

 feet and sometimes more in a mile. Those near Toronto are said 

 by Mr. Roy to preserve the same exact level for great distances, but 

 Mr. Lyell does not conceive that our data are as yet sufficiently 

 precise to enable us to determine the levels within a few feet at 

 points distant several hundred miles from each other. No fossil 

 shells have been obtained from these ridges, and the author concludes 

 that most of them were formed beneath the sea or on the margin of 

 marine sounds. Some of the less elevated ridges, however, may be 

 of lacustrine origin, and due to oscillations in the level of the land 

 since the great lakes existed, for unequal movements, analogous to 

 those observed in Scandinavia, may have uplifted freshwater strata 

 above the barriers which divide Lake Michigan from the basin of 

 the Mississippi, or Lake Erie from Ontario, or the waters of On- 

 tario from the ocean. Considerable differences of level may have 

 been produced in the ancient beds of these vast inland bodies of 

 freshwater, while the modern deposit and the subjacent Silurian 

 strata may to the eye appear perfectly horizontal. 



The author then endeavours to trace the series of changes which 

 have taken place in the region of Lakes Erie and Ontario, referring 

 first to a period of emergence when lines of escarpment like that of 

 Queenstown, and when valleys like that of St. Davids were exca- 

 vated ; secondly, to a period of submergence when those valleys and 

 when the cavities of the present lake-basins were wholly or partially 

 filled up with the marine boulder formation ; and lastly, to the re- 

 emergence of the land, during which rise the ridges before alluded 

 to were produced, and the boulder formation partially denuded. He 

 also endeavours to show, how during this last upheaval the different 

 lakes may have been formed in succession, and that a channel of the 

 sea must first have occupied the original valley of the Niagara, 

 which was gradually converted into an estuary and then a river. The 

 great Falls, when they first displayed themselves near Queenstown, 

 must have been of moderate height, and receded rapidly, because the 

 limestone overlying the Niagara shale was of slight thickness at its 

 northern termination. On the further retreat of the sea a second 



