316 Geology of the Valley of the St. Laiorence, fyc. 



examined, in company with Mr. Hall, the " Lake ridge," as it is called, 

 on the southern shore of Lake Ontario, and other similar ridges north 

 of Toronto, which were formerly explored by Mr. Roy, (see Proceed. 

 Geol. Soc. Vol. II, p. 537,) and which preserve a general parallelism 

 to each other and to the neighboring coast. Some of these have been 

 traced for more than one hundred miles continuously. They vary in 

 height from ten to seventy feet, are often very narrow at their summit, 

 and from fifty to two hundred yards broad at their base. Cross strati- 

 fication is very commonly visible in the sand ; they usually rest on clay 

 of the boulder formation, and blocks of granite and other rocks from the 

 north are occasionally lodged upon them. They are steeper on the 

 side towards the lakes, and they usually have swamps and ponds on 

 their inland side ; they are higher for the most part and of larger di- 

 mensions than modern beaches. Several ridges, east and west of Cleve- 

 land 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. Darwin off Bahia Blanca and 

 Pernambuco in Brazil, and by Mr. Whittlesey near Cleveland in Lake 

 Erie. They are supposed to have been formed and upraised in succes- 

 sion, 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 incline 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 be- 

 neath the sea or on the margin of marine sounds. Some of the less 

 elevated ridges, however, may be of lacustrine origin, and due to oscil- 

 lations in the level of the land since the great lakes existed, for unequal 

 movements, analogous to those observed in Scandinavia, may have up- 

 lifted fresh-water strata above the barriers which divide Lake Michigan 

 from the basin of the Mississippi, or Lake Erie from Ontario, or the 

 waters of Ontario from the ocean. Considerable differences of level 



