for agriculture, commerce has been wonderfully stimulated. Through Long
Island Sound there pass each day hundreds of boats which again and again
would suffer distress and loss if they were not protected from the open
sea. It is no accident that of the eight largest metropolitan districts
in the United States five have grown up on the shores of deep inlets
which are due to the drowning of valleys.

Nor must the value of scenery be forgotten in a survey such as this.
Year by year we are learning that in this restless, strenuous American
life of ours vacations are essential. We are learning, too, that the
love of beauty is one of Nature's greatest healers. Regions like the
coast of Maine and Puget Sound, where rugged land and life-giving ocean
interlock, are worth untold millions because of their inspiring beauty.
It is indeed marvelous that in the latitude of the northern United
States and southern Canada so many circumstances favorable to human
happiness are combined. Fertile soil, level plains, easy passage across
the mountains, coal, iron, and other metals imbedded in the rocks, and
a stimulating climate, all shower their blessings upon man. And with all
these blessings goes the advantage of a coast which welcomes the mariner
and brings the stimulus of foreign lands, while at the same time it
affords rest and inspiration to the toilers here at home.

CHAPTER IV. THE GARMENT OF VEGETATION

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. Although the soil has much to do with the character of
vegetation, climate has infinitely more. It is temperature which causes
the moss and lichens of the barren tundras in the far north to be
replaced by orchids, twining vines, and mahogany trees near the equator.
It is rainfall which determines that vigorous forests shall grow in the
Appalachians in latitudes where grasslands prevail in the plains and
deserts in the western cordillera.

Forests, grass-lands, deserts, represent the three chief types of
vegetation on the surface of the earth. Each is a response to certain
well-defined conditions of climate. Forests demand an abundance of
moisture throughout the entire season of growth. Where this season
lasts only three months the forest is very different from where it lasts
twelve. But no forest can be vigorous