MINERALS AND GEOLOGY OF CANADA. 453 
THE POST-TERTIARY DEPOSITS OF CANADA. 
Under this term, we include three series of deposits: the Drift or 
Glacial series, the Post-glacial series, and certain still more recent 
accumulations. These, though properly distinct, merge so gradually 
into each other, that no actual lines of demarcation can be drawn 
between them. 
The Drifé, or Glacial Formation proper, consists of thick beds of 
clay, sand, and gravel, with boulders or transported stones of various 
kinds and sizes, spread generally over the surface of the country, and 
extending on this continent to about 40° N. latitude. It does not ap- 
pear to contain any fossils. Those cited as belonging to it, come 
properly from Post-glacial deposits. When these Drift materials are. 
removed from the underlying rocks, the surface’ of the latter (where 
not in a partial state of disintegration) is generally found to be worn 
down, so as to present a smooth or even polished condition, and is 
traversed also by numerous thin lines or grooves, running in a ge- 
neral north and south direction—that is to say from some point between 
N. W. and N. E., towards the opposite direction in the south. The 
boulders vary in size from mere pebbles to masses of many tons’ 
weight, and consist of all kinds of rock. In some places they belong 
to rock-masses of the immediate locality, but far more generally they 
have been transported by some powerful agency from other and dis- 
tant sites. With the exception of certain mountainous localities, in 
which the boulder-courses radiate around central points, these travel- 
led stones have been derived (as regards the northern hemisphere) in- 
variably from northward-lying regions. In Canada, the greater num- 
ber of boulders consist of gneiss or other varieties of rock belonging 
to the great Laurentian area described in a preceding part of 
this Essay ; but where limestone or other strata occur in the im- 
mediate neighbourhood to the north, these gneissoid boulders are often 
mixed with pebbles and transported masses derived from the latter 
beds. Like the surface of the underlying rock, many boulders are 
smoothed down upon one side, and exhibit, upon this, delicate parallel 
furrows. Polished and striated rock-surfaces occur, in Canada, on the 
north shores of Lakes Superior and Huron; on the Blue Mountains, 
Collingwood township, at an elevation of about 1,500 feet above the 
sea; in the vicinity of Niagara Falls; the neighbourhoods of Belle- 
ville, Kingston, Marmora, Brockville, Ottawa, Montreal, Quebec; and 
