MINERALS AND GEOLOGY OF CANADA. 459 
submerged beneath the sea, during a portion at least of this period. 
The polishing and striation of the rocks may have been occasioned 
in part by glaciers, and in part by stranded icebergs; but the trans- 
portation of the boulders from the northern districts, southwards, 
must have been chiefly effected by the agency of the latter: just as at 
the present day, large masses of granitic and other rocks are dropped 
over the bed of the Atlantic by the melting of the icebergs on which 
they travel from the north. It should be mentioned that, as a general 
tule, these icebergs are nothing more than fragments detached from 
the extremities of arctic glaciers, where the latter reach the level of 
the sea. The stones brought down by these enormous ice-rivers, or 
broken off their rocky shores, collect in large heaps at their lower 
extremities, and many are thus floated off by the detached bergs, and 
conveyed over broad oceanic spaces to distant and more southern 
spots. That the country east of the gneissoid belt of the Upper 
St, Lawrence was beneath the sea to a depth of at least 500 feet at 
one period of this glacial epoch, is shown by the numerous deposits 
containing marine and estuary fossils, which occur, as explained above, 
throughout that area and the adjoming New England States. The 
same thing is proved also for both portions of the province, by the 
thick masses of drift clay, &c., which could only have been accumu- 
lated under water. As regards Western Canada—and this may pro- 
bably apply to eastern districts likewise—a gradual submersion of the 
Palzeozoic or more southern portion must first have taken place, since 
the lower clays are highly calcareous, and are evidently derived from 
the Silurian and Devonian strata immediately beneath or closely adja- 
cent to their areas of deposition. The depression still continuing, 
the higher lands and gneissoid strata of the north would be brought 
within the influence of the waves, and thus the sands, gravels, and 
boulders of the Upper Drift deposits, would be gradually accumulated, 
A re-sorting of these materials must have occurred to some extent 
during the subsequent elevation of the country, producing, in part, 
the various post-glacial deposits; although in the western region, 
most of these latter must have been formed by the great lake-watergs 
whic extended over this area, as described on a preceding page, after 
the final elevation of the land. The cold of the Drift period, with 
its accompanying phenomena, came on gradually, and as gradually 
diminished in intensity ; or, in other words, these glacial manifesta. 
tions shrunk back slowly, after a certain lapse of time, to within the 
