Athabasca, and Lake Winnipeg to the Lake of the Woods, which
drains into Lake Superior. All these lakes lie on the edge of the
great Laurentian shield, where the ice, crowding down from the
highland to the north and east, was compressed into certain
already existent hollows which it widened, deepened, and left as
vast bowls ready to be filled with lakes.

South and southwest of the Laurentian highland the great ice
sheet proved beneficial to man. There, instead of leaving the
rock naked, as in the Laurentian region, it merely smoothed off
many of the irregularities of the surface and covered large areas
with the most fertile soil.

In doing this, to be sure, the ice-cap scoured some hollows and
left a vastly larger number of basins surrounded in whole or in
part by glacial debris. These have given rise to the innumerable
lakes, large and small, whose beauty so enhances the charms of
Canada, New England, New York, Minnesota, and other States. They
serve as reservoirs for the water supply of towns and power
plants and as sources of ice and fish. Though they take land from
agriculture, they probably add to the life of the community as
much in other ways as they detract in this. Moreover glaciation
diverted countless streams from their old courses and made them
flow over falls and rapids from which water-power can easily be
developed. That is one reason why glaciated New England contains
over forty per cent of all the developed water-power in the
United States.

Far more important, however, than the glacial lakes and rivers is
the fertile glacial soil. It comes fresh from the original rocks