\ 
316 Geology of the Valley | 
if “the St. Lawrence, §c. 
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, an times 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 ina mile. Those near Toronto are said by Mr. 
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 t0 _ 
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 
