leys have provided good harbors, but these do not drain large land areas as do the harbors in the east. Of course it is desirable that the countries with which one wishes to trade shall also be favored with good harbors connected with advantageous means of internal communication.

Physical features also influence commerce indirectly by determining the particular commodities which may be profitably produced in a region; but a discussion of this subject would involve the details of commercial geography and would be beyond the scope of a discussion of general principles.

Of all the economic factors influencing the growth of cities commerce seems to support the largest population, therefore the greatest cities arise on good harbors or on natural internal points of distribution. Such cities have the greatest accumulation of wealth and tend to become centers of intellectual and social progress.

Environment Determines Distribution of Population. In addition to its direct effect upon occupations, the physical environment influences in other ways the numbers and distribution of peoples. In the first place the size of a population is affected by the amount of land available. To be sure quality of land and climate are of the utmost importance; but, if these factors do not vary, the larger land mass not only provides more area for expansion but usually furnishes also variety of territory and therefore of products. A glance at the map shows that the northern hemisphere is much superior to the southern in land

Not only is this absolutely much larger in the northern hemisphere, but the relative amount situated in the temperate zone is still greater. In the southern hemisphere the continents taper off in the temperate zone, while in the northern they broaden out. It has been no mere matter of chance that the centers of civilization and progress have been located in the northern hemisphere.

Effects of Climate upon Early Civilizations. The next factor to affect civilization after the land itself is climate. The influence of climate upon civilization follows logically its influence upon the individual already described. In the tropics groups easily survive, but the progress of culture is exceedingly slow. The most notable advances in civilization were made in hot, dry regions where the climate is somewhat more stimulating, but where physical needs are still comparatively simple, and where there is no marked change in severity of seasons. Particularly favorable were those spots where nature herself provided moisture through the overflow of rivers, as in the Nile Valley and in the Tigris-Euphrates basin. Civilization in colder and more variable climates came later, after the arts of life were more fully developed, so that the conquest of nature was easier. The importance of the climatic influence in different periods is shown by the striking fact that progress, as measured by centuries, has been marked by a gradual transition of dominant peoples, and with them the zone of great cities, from southern to northern latitudes. The movement has been away from the equator towards a climate which was inferior for the beginnings of civilization, but which came to be superior after man had made considerable technical progress. And the movement was northerly rather than southerly because of the extensive land areas and their generally favorable topography.

The northerly movement finally reaches a natural limit, however, when unfavorable physical factors overbalance favorable, even for civilized man. The decreasing ratio of warm days to cold, the greater intensity of the cold, and the uneven distribution of light and darkness make living conditions more severe and less attractive, so that as civilization tends to advance northward a reverse movement may be detected back to the milder parts of the temperate zone. This reverse movement is connected also with a third factor, healthfulness. In their original states some of the warmer climates were less salubrious than the colder, for many disease germs survive and multiply best in hot places. But a notable phase of recent progress in the arts has been the growth of knowledge as to the causes of disease and the ability to control them. In the future therefore the most delightful climates may become also the most healthful, and this fact will have an important bearing on the distribution of populations.

A statement of the influence of any one factor in progress always seems to over-emphasize the importance of that factor and make the conditions of progress appear much simpler than they actually are. And the climatic factor is not such a simple and direct influence as it may seem, for it acts not merely in conjunction with other environmental factors but is linked with social relations which cannot be discussed in detail here. Civilization originated in hot climates, to be sure, but it was founded on forced labor obtained through conquest; while the civilization of temperate zones has been built largely on free labor. Of course social relations themselves in the last analysis are affected, if not determined, by climate and other physical factors, all of which are complicated and far reaching. But the advantages of climate are at best relative, depending upon the character of the people and upon the degree of their social advancement. When we speak without qualifications of the advantages or disadvantages of a climate, we are unconsciously viewing it in relation to our own population and our own stage of social development. Yet with all these reservations it cannot be denied that climate is a potent factor in progress and has been through all stages of civilization.

The Advantages of Isolation. Next in importance to climate is the influence of location upon a people with reference to isolation or accessibility. Mountains, swamps, or deserts form barriers to intercourse between peoples, while valleys and navigable rivers make it easy. In the early stages of civilization the presence of barriers seems to have been advantageous for two reasons: first, they protected a people from liability to attack, thus giving them better opportunity to develop their own industrial and social organization; and, secondly, they caused them to concentrate in small areas, thereby stimulating intensity of social life. Both these influences have been apparent in the early history of civilizations. Mention has already been made of the favorable climatic conditions of Egypt, but this country was also well favored with barriers, with the desert on the one side and the mountains on the other, which preserved it from frequency of attack from hostile peoples. England is another example of a nation which has been greatly favored through isolation, in this case because of its insular position. The early development of England was due largely to the fact of

its comparative freedom from attack, while the late development of Germany is traceable to the confused conditions resulting from the continuous wars which its easy accessibility to its neighbors made inevitable.

The importance of barriers in causing concentration of peoples is well illustrated by the American colonies. The Appalachian Mountains kept the population from spreading and it developed, in a narrow and diversified belt, the beginnings of an industrial and commercial life which clashed with the interests of the mother country. At the same time its increasing intensity of association tended to waken radical views and keep alive hostility to England. North of the Appalachian Mountains, where the population spread out into the St. Lawrence Valley, little hostility developed. And south of the mountains, where on the broad coastal plains again the population was scattered, there existed the greatest degree of conservatism and loyalty to the mother country. Shaler thinks that the American Revolution would have been greatly delayed had it not been for the Appalachian barrier. And it is easy to go even farther and to imagine that economic and political conditions might in that case have been so different that the Revolution would never have taken place.

So important to early civilizations was an area with natural protections, that sometimes peoples who have been driven out of rich territories and been obliged to take refuge in poorer but inaccessible locations, have developed there a higher civilization. Such was the case with the Quichuans who reached a high stage of development in the mountains of Peru, where the environment though difficult ensured freedom from attack. And in ancient and mediaeval times the sites deliberately chosen for the location of cities were usually inaccessible ones, which could be easily defended, in preference to low richer sites more open to attack.

The Advantages of Accessibility. Extreme isolation, which in early times proved advantageous, in later times may become disadvantageous, since continued progress depends so greatly

1 N. S. Shaler, Nature and Man in America, p. 199. See also E. C. Semple, American History and its Geographic Conditions, pp. 46 and 47. upon free intercourse between peoples. The remarkable development of early civilizations in the Mediterranean basin is usually attributed to the excellent means of communication which made possible a stimulating intercourse among dissimilar peoples. Greece was particularly favored in this respect. The numerous indentations of the coast offered many harbors and excellent protection for early navigation. And the islands in the Aegean Sea are so numerous that navigators could make their way to Asia Minor without losing sight of land. However, other enclosed seas affording similar advantages are to be found off the coast of Asia, and in other parts of the world; and the fact that civilization did not develop to the same extent in other enclosed areas would suggest again that favorable climate was more important than intercourse as a stimulus to the appearance of civilization. But, after civilization has once made a good start in a favorable climate, continued progress is particularly dependent upon accessibility.

The most advantageous location of all would seem to be one which offers natural means of defence and at the same time permits a wide amount of intercourse. Such is the situation of England, for its insularity is a safeguard, yet the sea does afford possibility of communication with a much larger number of countries than would ever be possible by land routes. It should be noted that an area which is quite isolated at one period of social development becomes less and less isolated as methods of communication improve. Not only England, but the United States also, is much less isolated from Europe than it formerly was. Our “fortunate isolation,” which preserved us from attack, no longer exists; and our interests and welfare are more and more at one with those of other countries. Nevertheless our isolation in the past has wonderfully favored our development. If we had been obliged to maintain a militaristic state we could not possibly have developed economically as we did.

Russia is an example of a country which has been retarded not merely because of its unfavorable climate, but because of its land surface which permits its inhabitants to scatter. The population though large is not concentrated in cities and therefore lacks both the industrial and intellectual development which