The production of wealth is influenced seriously by the fact that the various materials and forces of nature are not uniformly distributed over the earth's surface. The unequal distribution of heat and cold in place and time gives us the zones and seasons which have marked consequences in the field of production. Then, too, the mountains and the plateaus and the valleys and the rivers and lakes furnish different occupations to different groups of people. The winds and the waterfalls lighten the problems of production for those in a position to take advantage of them. One kind of soil is suitable for one product and another kind for another. Navigable rivers make it easier to develop the resources of a continent. Good ocean harbors build up prosperous commercial cities. In these and in thousands of other ways physical geography influences production.

43. Categories Of Land

Because of the variety of ways in which nature is active in production it will be useful to consider productive land as of several classes: agricultural land, which is used to grow crops; grazing land, upon which flocks and herds feed; forest land, from which timber is obtained; mining land, from which minerals are secured; roadways, which serve as means of communication; city land, the main use of which is to serve as a support for buildings, and so forth; and rivers and lakes and oceans, each of which makes its contribution to man.