214 A POPULAR EXPOSITION OF THE 
the Drift and succeeding deposits ; 
but it may be observed that the 
more recent of these accumulations 
contain shells of the wnio, cyclas, 
melania, and other fresh-water 
types now inhabiting the river, and 
evidently indicate, as first pointed 
out by Sir Charles Lyell and Pro- 
fessor James Hall of Albany, an w 
ancient and at one time continuous Fie. 224. 
deposit spread over the original 
river-bed. Accumulations of a similar character occur, however, im 
various parts of the Western Province, and were produced by our 
lake waters when these were united into one vast fresh-water sea, as 
explained in a subsequent part of this Essay.* 
The limestones of the Niagara Formation yield excellent building 
materials, and quarries have been opened in these beds at Rockwood, 
Owen Sound, and other places. 
In Eastern Canada, the Niagara strata, or rocks of the same geolo- 
gical horizon, are thought to occur in Gaspé, on the Chatte, Rimouski, 
and other rivers, and on Lake Metapedia; but much uncertainty still 
prevails with regard to the true position of these beds. They form 
the lower portion of the strata provisionally known as the “Gaspé 
limestones.” In the Island of Anticosti in the Gulf of the St. Law- 
rence, however, there is a great display of limestone rocks undoubt- 
edly of Middle Silurian age: the equivalents consequently of the 
Medina and Clinton, combined with the Niagara Formation. Along 
the more northern shore of the island, there runs a belt of Hudson 
River strata, as explained in our remarks under that formation; and 
this is succeeded by the limestones in question. These, with a few 
interstratified shales, occupy all the rest of the island, and make up, 
according to Mr. Richardson of the Geological Survey, a thickness of 
nearly 1,400 feet. The numerous fossils which they contain, have 
on the whole an essentially Upper Silurian character, but certain 
forms amongst them appear to establish a connecting link or passage 
between the Lower and Upper subdivisions of the Silurian series as 
* See a paper by the writer, on the ancient extension of our lake area, &c., in the Philo- 
sophical Magazine for July, 1861, and in the Canadian Journal, Vol. V1., p, 221. Also an 
article by Robert Bell, of the Canadian Geological Survey, in the Oanadian Naturalist 
Vol, VI. 
