uld thus cover the entire surface of
the country, burying alike the valleys and the hills. The mass of ice
that moved slowly, century by century, across the face of Southern
Canada to New England is estimated to have been in places a mile thick.
The limit to which it was carried went far south of the boundaries of
Canada. The path of the glacial drift is traced by geologists as far
down the Atlantic coast as the present site of New York, and in the
central plain of the continent it extended to what is now the state of
Missouri.

Facts seem to support the theory that before the Great Ice Age the
climate of the northern part of Canada was very different from what it
is now. It is very probable that a warm if not a torrid climate
extended for hundreds of miles northward of the now habitable limits of
the Dominion. The frozen islands of the Arctic seas were once the seat
of luxurious vegetation and teemed with life. On Bathurst Island, which
lies in the latitude of 76 degrees, and is thus six hundred miles north
of the Arctic Circle, there have been found the bones of huge lizards
that could only have lived in the jungles of an almost tropical climate.

We cannot tell with any certainty just how and why these great changes
came about. But geologists have connected them with the alternating
rise and fall of the surface of the northern continent and its altitude
at various times above the level of the sea. Thus it seems probable
that the glacial period with the ice sheet of which we have spoken was
brought about by a great elevation of the land, accompanied by a change
to intense cold. This led to the formation of enormous masses of ice
heaped up so high that they presently collapsed and moved of their own
weight from the elevated land of the north where they had been formed.
Later on, the northern continent subsided again and the ice sheet
disappeared, but left behind it an entirely different level and a
different climate from those of the earlier ages. The evidence of the
later movements of the land surface, and its rise and fall after the
close of the glacial epoch, may still easily be traced. At a certain
time after the Ice Age, the surface sank so low that land which has
since been lifted up again to a considerable height was once the beach
of the ancient ocean. These beaches are readily distinguished by the
great quantities of sea shells that lie about, often far distant from
the present sea. Thus at Nachvak in Labrado