The Negro, however, has been tested on an extensive scale.

It will be a vast boon to mankind when we learn to prophesy the precise dates when cycles of various kinds will reach definite stages.

The whole history of life is a record of cycles.

Geologists are rapidly becoming convinced that the mammals spread from their central Asian point of origin largely because of great variations in climate.

Year by year we are learning that in this restless, strenuous American life of ours vacations are essential.

Except on their southern borders the great northern forests are not good as a permanent home for man.

No part of the world can be truly understood without a knowledge of its garment of vegetation, for this determines not only the nature of the animal inhabitants but also the occupations of the majority of human beings.