North American Laurentia has no soil worth mentioning. For some
reason not yet understood this was the part of America where snow
accumulated most deeply and where the largest glaciers were
formed during the last great glacial period. Not once but many
times its granite surface was shrouded for tens of thousands of
years in ice a mile or more thick. As the ice spread outward in
almost every direction, it scraped away the soil and gouged
innumerable hollows in the softer parts of the underlying rock.
It left the Laurentian highland a land of rocky ribs rising
between clear lakes that fill the hollows. The lakes are drained
by rapid rivers which wind this way and that in hopeless
confusion as they strive to move seaward over the strangely
uneven surface left by the ice. Such a land is good for the
hunter and trapper. It is also good for the summer
pleasure-seeker who would fain grow strong by paddling a canoe.
For the man who would make a permanent home it is a rough,
inscrutable region where one has need of more than most men's
share of courage and persistence. Not only did the climate of the
past cause the ice to scrape away the soil, but the climate of
the present is so cold that even where new soil has accumulated
the farmer can scarcely make a living.

Around the borders of the Laurentian highland the ice
accomplished a work quite different from the devastation of the
interior. One of its chief activities was the scouring of a
series of vast hollows which now hold the world's largest series
of lakes. Even the lakes of Central Africa cannot compare with
our own Great Lakes and the other smaller lakes which belong to
the same series. These additional lakes begin in the far north
with Great Bear Lake and continue through Great Slave Lake, Lake