the influence of the various substances held in solution of the water, as salt, oxygen, carbonic acid, etc. The ova of different and yet very closely related forms can endure a long period of drought, or even require it to enable them to develop. Hence, every change, as for instance, in the composition of the water of a lake or river will not affect the fauna inhabiting it equally and as a whole, but will act on some individuals; some will bear the change without being in any way affected by it, others will die, while others again will survive.” 17

We must now consider more directly in what ways man himself is influenced by the physical world and for purposes of discussion we may divide this into five heads: (1) distribution and migration, (2) occupation, (3) direct physical effects, (4) physiological effects, (5) psychical effects.

1. Distribution and Migration.-The common belief is that the human race arose in some one area. Even if this be true, we must recognize that in prehistoric times man had made his way to every part of the earth. Though the density of population turns in part on the stage of culture, it is interesting to note his present distribution.

Approximate Density of World's Population, 1911

The frigid zones, deserts, high mountain ranges,

17 SEMPER, K. Animal Life, p. 176.

swamps, water surfaces are sparsely populated, if at all. Most mountain districts impose hard conditions upon men. In Switzerland the mountain cantons show the smallest population per square mile (Grisons, 38; Uri, 48; Valais, 59); while those on the marginal plains are relatively crowded (Zurich, 705; Geneva, 1,356). In England: Westmoreland (85); in Wales: Radnor (49); and in Scotland, Sutherland (11) again show the hill country, for the average density in Great Britain is 374. In Switzerland only 15 per cent of the land can be cultivated and the same is true of Japan. In Norway 67 per cent of the total area is in bare mountains, lakes, snow fields or bogs, 7.6 per cent in pastures, 2.2 per cent in meadows and 7 per cent in grain fields. The dense populations of earth are found in the lowlands below an elevation of 600 feet: in China, the valleys of India, the valleys of the Po, the lowlands of France, Germany and England where the population is over 385 per square mile. The different states in America show the same contrast. We may compare Rhode Island (508), Massachusetts (418) and New Jersey (327) with Montana (2.6), Idaho (3.9) and Louisiana (36.5). Wherever a heavy population is found in the Piedmont between the lowlands and the mountains it is due to the development of mineral resources. Birmingham, Alabama, is a good illustration of this. Unless forced by his enemies or driven by pressure of population, man is very slow to enter the mountains as places of permanent residence. Hence any group getting located in the mountains is likely to drop out of touch with the development of the balance of the country and become "our contemporaneous ancestors as the inhabitants of the southern Appalachians have been called.

Man's movements on earth have been directed and controlled by physical conditions. High mountain ranges have offered next to the ocean the greatest barriers. Hence has arisen in human history the importance of passes. Thermopyla renowned in Greek literature, the Brenner Pass through which the Germans made their way to the Po Valley, the Dariel Pass in the Caucasus, the Cumberland Gap, the Mohawk Valley and Truckee Pass, through which the California trail in the 40's led, are but a few of historical importance.

In times of peace the passes are the great trade routes determining the location and prosperity of many settlements. The Brenner Pass was largely responsible for the commercial life of Augsburg, Ratisbon, Nuremberg, Leipzig and, in part, Venice. Through the low Mohawk Valley, 445 feet above sea level, was the line of march to the Great Lakes and the West. The district became densely populated while the neighboring Catskills were nearly empty. Because of this great highway Albany, Troy, Utica, Rochester and Buffalo came into being. Had the St. Lawrence been navigable to the lakes and its mouth free from ice the entire development of North America would have been changed, so much does nature determine man's movements. First the animals for ages making their way through the hills, then uncivilized man in pursuit of game, then the trapper and frontiersman following in their trail; then probably the army officer discovering a pass and then the surveyor and the railroad, all following the road indicated by nature. In dozens of places on earth just this development has ensued. For long ages navigable rivers have been favored highways. Wherever the fall line was encountered at the edge of the hilly Piedmont country there too has man

built his towns. The Atlantic Ocean has a drainage basin of over 19,000,000 square miles, while the Pacific has only 8,660,000. Rivers facilitate trade and intercourse. Africa has nothing to compare with the Amazon or the Missouri. The Yangtse and Hoangho are the source of China's prosperity as was the Nile of ancient Egypt.

Islands in favorable climes are densely populated. Java has a density of 587 to the square mile; Gilbert Islands of Great Britain, 1254. The Islands of Denmark have a density of 269 as compared to 112 in Jutland on the mainland. Safety and fish are probably the two chief factors in causing this density.

Until the sixteenth century the oceans were practically impassable, until the nineteenth, impassable to all but a handful; yet man has at some time and somehow made his way to all habitable parts of the earth.

2. Occupation." Geographic conditions influence the economic and social development of a people by the abundance, paucity or general character of the natural resources, by the local ease or difficulty of securing the necessities of life, and by the possibility of industry and commerce afforded by the environment.” 18 The history of America affords endless illustrations of the truth of this statement. The New England States turned from agriculture to manufacturing and shipping, they found slavery generally unprofitable and they developed the town and town meeting as their type of government; while substantially the same people in the south clung to farming largely because of the adaptability of the land to tobacco and cotton, welcomed the Negro slaves and made the county the unit of government, the scattered house

18 SEMPLE, E. T. Influences of Geographical Environment, p. 43.

hold the ideal of life. There is no more interesting contrast in our history than the antagonisms between the hill whites and the lowland slave owners, indicated by such events as the separation of West Virginia from the mother state and by the fact that some of the mountain counties of Tennessee furnished as large a percentage of Union volunteers in proportion to population as did any northern district. Since man must live on the "free goods" of nature to be had by the taking or must produce for himself, it is easy to see that the life of the Eskimo must differ widely from that of the West African Negro. In Polar regions man must even today be a fisher and hunter, living on meat alone, unless he keep in touch with other people, when he may be a miner. On the whole the temperate zones have been most favorable to him, and no great civilization has arisen as yet in the tropics. By fixing the opportunities nature goes far towards determining the type of the development.

3. Direct Physical Effects.—“We can hardly err in attributing the great lung capacity, massive chests and abnormally large torsos of the Quichua and Aymara Indians inhabiting the high Andean plateaus to the rarefied air found at an altitude of 10,000 or 15,000 feet above sea level." 19 It is well known that the different parts of the body grow and mature at different rates and times. If food, heat or clothing be lacking, a stunting may result. Alpine or boreal races are usually shorter than those of the lowlands of warmer regions. Transfer to a new country may cause marked changes for reasons not yet fully understood. In America the descendants of Europeans are seemingly considerably larger than the average at home. This was indicated by the soldiers in 19 SEMPLE, E. T. o. c., p. 34 ff.