REGARDED in their relation to man, the different regions of the earth may be arranged under two general types. Some seem to repel man, who does not establish cities or large states in them. Their inhabitants lead a kind of vegetative existence, often as nomads, always thinly scattered, and poor if not wretched, with no aspirations beyond material existence. Other lands, on the contrary, seem to attract human life. Men flow to them from all quarters, as the blood from the extremities to the heart. They collect in opulent cities, and build up powerful states in which brilliant civilizations develop. But only a superficial glance over history is sufficient to enable us to recognize that these centers of resort and centers of dispersion change their places in the course of ages; and on every side we behold them undergoing alternations of grandeur and decay; countries once resplendent with glory are now deserted and wretched, while men are thronging toward regions which they formerly persistently avoided. The reason of these contrasts is to be found in the complex relation between the land and man. If man goes to one place in preference to another, it is because he finds there a fuller satisfaction of his desires and wants. To obtain the largest sum of enjoyment at the price of the smallest expenditure of effort is essentially a law of man's life. We may, therefore, conclude that if man turns away from a region to which he was once attracted it is because the resources of the country have become, in his eyes, relatively less valuable.
The study of the relations between man and the earth comprehends three parts: the determination of the factors on which the value of the relation depends; the variations of the relation and the inquiry whether it tends toward a limit, and, if so, toward what limit. The men who people the surface of the earth do not appear to have any great resemblance to one another, but the different races present very dissimilar physical characteristics and mental aptitudes. Yet these contrasts are purely superficial. At bottom all men are indifferently subjected to the same general conditions of existence and development. These conditions are of various kinds: some are essential in the nature of necessities that impose themselves on all animal life — such as the impossibility of subsisting without a certain quantity of air, warmth, and moisture, and vegetable or animal food; other conditions, still important but less essential, are those which, without directly influenc-
- A paper read in the Congress of Scientific Societies, France.