In high latitudes in all parts of the world the land has recently been submerged beneath the sea. In some places, especially those like the coasts of Virginia and central California which lie in middle latitudes, a recent slight submergence has succeeded a previous large emergence. Wherever such sinking of the land has taken place, it has given rise to countless bays, gulfs, capes, islands, and fiords. The ocean water has entered the valleys and has drowned their lower parts. It has surrounded the bases of hills and left them as islands; it has covered low valleys and has created long sounds where traffic may pass with safety even in great storms. Though much land has thus been lost which would be good 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.