which on our maps today is covered by Afghanistan, Baluchistan, and the Persian and Turkish Empires-been governed by its position as a narrow causeway between the populations which grew up in the river basins of China and India and the populations which developed on European islands and peninsulas, large and small, old and new, from the days of the Phoenician galley to the days of the English tramp steamer.

The primal basal fact in regard to any part of the earth's surface, the fact which conditions all the rest and inexorably determines and defines human development, history, and civilization, is whether it partakes in its coast line of the Atlantic or Pacific Coast type. The first type, now a familiar commonplace in geography, is represented by coasts like those of the Atlantic, of which the eastern coast of North and South America is the standard, which show a minimum of change, constituting an even coast-line in which the hundred-fathom line through most of its course preserves so steadfast a distance from soundings that the position of a vessel can over most of this area be instantly, though approximately, determined by its discovery. Such a coast is

continuous in its outline, quiescent in its mutations, unbroken in its development. To such a coast-line history can be transplanted. On such a coast-line history has never originated. The sig

nificant example of the Pacific type of coast, on the other hand, is represented by the western half of that rim of fire which girdles the Pacific and which gives the eastern coast of Asia its island continent and the successive volcanoes which appear at brief intervals from Krakatoa to the Arctic Circle. This type marks the true coast of Asia; on the east it exists in northern India, and reappears in one of its most characteristic forms on the northern edge of the Mediterranean. If we reproduce here a summary

of the distribution of these types of coast,' it is immediately apparent that the coast of China, the region in north India in which its two great river valleys lie, and the Mediterranean region are connected by a narrow strip of such coast along the Persian Gulf and the Bay of Bengal of the same mobile type. On the other hand, the east coast of Africa, all the coast of Arabia, including that on the Red Sea, represent coasts of an

9 Der Atlantischer und Stiller Ozean Typus.

immobile type, in which fluctuations of surface have long since reached a comparative equilibrium. Where the coast is mobile, changes in the coast constantly occur. There the coast will be irregular, and the approaching and penetrating sea will carry

Into every bare inlet and creek and bay

contact and the seeds of development. The northern coast of the Eurasian region is bounded by an immobile coastline, and its area for 2,000 miles inland is of a monotonous character, which renders communication or the diversification of type difficult. The development of any race comes where there is a diversity of physiographic conditions. therefore significant that the three city regions already noted are joined at only one point along southwestern Asia by a strip of territory under physiographic conditions similar to their own. This is, of course, only another way of saying

that the Taurus, Caucasus, and other ranges of the region are part of that same new uplift which decides the northern outlines of the Mediterranean and fixes the sources of the great river systems of Asia. In its fundamental characteristics, therefore, this region partakes of those coast conditions which exist in the three regions of which it is a link. is provided with mountain ranges of a similar structure, running in the same general direction, presenting the same general aspect, and furnishing, therefore, the soil for transmission of common ideas and a similar social structure.

RAINFALL AND DEVELOPMENT

Rainfall determines the limits of human development. The rainfall of the world extends from a precipitation of from three to five inches up to ten feet; but the limits of this rainfall within which any civilization is possible are narrow. They extend practically from

15 to 20 inches up to 45 or 50. With a rainfall of 50 inches few civilizations exist. With a rainfall of over 50 inches civilization is drowned out. A rainfall of less than 10 or 15 inches renders cultivation impossible unless irrigation is conducted on a large scale, and this involves either complete isolation from disturbance on the part of small communities or a share on the part of a small community in the security and capital of a larger nation, with sufficient resources to carry out an extensive project of irrigation. If, as in this map," which presents rainfall, the average annual precipitation be distributed into a rainfall of under 25 centimeters, from 25 to 50 centimeters, from 50 to 100 centimeters, and over 100 centimeters, it will be seen that the civilized and developed regions of Asia and Europe have a rainfall of from 50 to 100 centimeters; but there lies between them a broad area of a rainfall of under 25 centimeters; and that the region which we have been considering has over it a strip of rainfall of 25 to 50 centimetersa mean between the rainfall in which civilization is impossible and that under which it best flourishes. Where a rainfall as small as this falls over a broad tract of uniform modeling, it will be so distributed and diffused as to do little more than create brief green patches in the winter and spring. Where, however, it meets any medium mountain range creating valley areas, a rainfall of this character will be so collected as to give fertile river valleys essentially insular in their character, which will be sheltered from disturbing invasion by stretches around less easily traversed and in some respects, as in the desert west of Egypt, a greater protection than any ocean deep. Such a stretch of reduced rainfall over a mountain tract would constitute, therefore, another of

19 Jahrliche Niederschlage Mengen in “Grundzuge Physischen Erdkunde," Supan, L., 1897, Taf. XI.

the link conditions which unite the heavier precipitation under which civilization develops.

RAINFALL AND MOUNTAIN TRACTS

So far as precipitation is concerned, therefore, the three centers of the Eurasian system are separated by regions of insufficient rainfall north and south. Across these, just north of that high barometric area along the thirtieth parallel, which constitutes so important a climatic influence in the North Temperate Zone, stretches a region of medium rainfall for which the mountain system of southwestern Asia gives exactly the conditions which permit the early development of isolated civilizations in a region where the development of man is not impeded, as it is over the forest region which once stretched from the Pacific to the Atlantic across the Eurasian system or by the desert region to the south. At this point, therefore, the hypsometric conditions coöperate with the rainfall produced by the distribution of isobars and other causes to create in this linked region the opportunities, not for extensive and heavy population, but for nests and centers of population. Climate, which is rainfall plus place and temperature, enforces this condition still more clearly. The Mediterranean basin constitutes a distinct climatic region, separated on the one side from the steppe climate of eastern Europe and from the moderate climate, due to warm currents of air, in western Europe. India and the island world to the southeast constitute another climate, not unlike in its uniform conditions to the Mediterranean basin, though wholly unlike in its temperature and precipitation. This has to the north the steppe climate of central Asia and the climate of China, as with that of Europe, modified by air drifts. Between these two regions, as the distribution of climate by Supan shows, the mountain region, extending from the