America forms the longest and straightest bone in the earth's skeleton.
In America the most widespread type of forest is the evergreen coniferous woodland of the north.
The coast of British Columbia was one of the three chief centers of aboriginal America.
Thus the races, though alike in their physical response to climate, may possibly be different in their mental response because they have approached America by different paths.
America is the last great goal of these migrations.
From first to last the civilization of America has been bound up with its physical environment.
The human organism inherits so delicate an adjustment to climate that, in spite of man's boasted ability to live anywhere, the strain of the frozen North eliminates the more nervous and active types of mind.