Food, raw materials, fuels, metals, and manufactured goods forni a series of increasingly complex products. The simplest ,savages and even the animals use food. When primitive man began to fashion raw materials into shelter and clothing he took one of the first great steps toward civilization. When he found out how to make fire and thus began to use fuel he took another. Next he used his fire to smelt metals which led the way to the making of good tools and machines. The last stage was to use the tools and machines for the complex proc esses of modern manufacturing. The business of the world consists largely of the interchange of these five types of products between people of different regions, different occupations, or different stages of development.
The Conditions that Govern kind, quantity, and quality of the products of a region depend partly on nature and partly on man, as appears in the following tabular view : The four natural factors explain themselves. Among the three human factors, racial character includes not only the inherited abilities of the rank and file, but the proportion of men of genius; training depends on social environment, including education, government, religion, and historical development; while energy is a matter of health and inheri tance. No one factor works alone, for the production of a region is generally the result of a combination of all seven. Although each factor can most easily be studied separately, its effect is greatly modi fied and often neutralized by that of others. For example, climate has far more effect than any other physical condition upon the pro duction of plants and animals; but the character of the people who live in a place like Hawaii may cause the products to differ from those found in similar climates elsewhere.
Climatic Optima as a Primary Factor in the Production of Food and Animals.—Everyone knows that plants and animals vary according to climate. Corn thrives in the sunny showery summers of Iowa, but not in the equally moist but cooler summers of Scotland. Palms and pines thrive best under such widely different conditions that their presence together is a theme for the poets. The two-humped Bactrian camel is extraordinarily well adapted to the dry desert and can stand the most intense cold. But in snow or mud the great brute sometimes slips until it falls on its stomach with its legs stretched out in front and behind, thus breaking a tendon so that it has to be killed. When the nomads of Central Asia graze their camels among the moist mountains they protect them from the drizzling rain with huge woolen blankets, for otherwise the beasts would be chilled and die, even in summer.
The Optimum for. Corn.—Every plant and animal has what is called an optimum climate, that is, a certain temperature, humidity, varia bility, and degree of sunshine under which it thrives best. The area of greatest production of corn in the U. S. has an average summer temperature of about 75°, which may be considered not far below the optimum temperature of greatest growth. Corn needs not only a
high summer temperature, but requires about 140 days without frost. Such conditions are found where the temperature of the germinating and ripening seasons averages approximately 55° or 60°. The opti mum rainfall is enough to keep the ground moist though not water logged during rapid growth, but less when the full-grown ears are ripening. The average rainfall in the corn belt during the critical period of July when the ears are developing is about 4 inches. A moderate increase raises the production, but a great increase does not produce a corresponding effect. On the other hand, a slight decrease below 4 inches decreases the corn crop. Thus the optimum July rainfall appears to be more than 4 inches but less than 8. This abundant rain fall must not be accompanied by great cloudiness, for that stunts and rots the corn. Hence the optimum is warm sunny weather interspersed with frequent showers. A close approach to these optimum conditions causes eastern Nebraska, Iowa, Illinois, and Indiana to be the great corn region of the world. Certain tropical regions may approach the optimum still more closely, although their present yield per acre is less than in the United States because of poor cultivation.
The fineness of the soil, the levelness of the plain, and the skill of the farmer also have much to do with the abundance of the crops, but they are not the main factors. This appears from the fact that although Manitoba and eastern Colorado rival the corn states in soil, in levelness, and in the skill of the farmers, they produce little corn. Manitoba is too cool, Colorado too dry. This can be seen in Fig. 1, where dotted lines indicate an average temperature of F. and a total rainfall of 8 inches for the three summer months of June, July and August.
South of the temperature line the climate is sufficiently warm so that corn flourishes. East of the rainfall line there is moisture enough. North and west of the lines, because of low temperature and light rain fall, corn grows only in very small quantities.
The climatic optima for corn help to explain why the Ohio farmers are so prosperous; why Iowa raises over 40 hogs per farm and Wyo ming only 8; why corn cakes are the great bread-food of Mexico, and why Hungary is the chief corn country of Europe.* The Optimum for Horses.—The climatic optima of animals are not so evident and have not been studied so carefully as those of plants, but they are just as real and important. We have already seen how the camel usually loses his value when taken into a climate where rain or snow is common. In the same way the horse does not thrive every where. When a horse is brought from Texas to Boston, for example, he is often somewhat sickly at first and has to be acclimated. But neither Texas nor Boston has the kind of climate most favorable to horses. In the wild state the horse thrives best in a climate too dry