CLIMATE AND HUMAN ENERGY How Climate Affects Man Directly.—Man's health and energy depend on climate and weather more than on any other single factor. The well-known contrast between the energetic people of the tern-. perate zone and the lazy inhabitants of the tropics is due to climate. It is impossible for a people to advance rapidly in civilization when handicapped by an enervating tropical climate, and even the climate of intermediate regions like Persia, tends strongly to keep people back ward.
The best way to understand how climate influences health and energy is to consider how the weather causes our own condition to vary from day to day and season to season. Although some people are more affected than others, everyone is influenced by temperature, humidity, wind, sunshine, barometric pressure, and perhaps other factors such as atmospheric electricity and the chemical composition of the air. On days when all these factors are favorable, people feel strong and hopeful; their bodies are capable of unusual exertion, and their minds are alert and accurate. If all the factors are unfavorable, people feel inefficient and dull; their physical weaknesses are exagger ated; it is hard to concentrate the mind; the day's work drags slowly; and people go to .bed at night with a tired feeling of not having accomplished much. Hence in variable climates like that of the United States people's physical and mental energy keep changing from day to day and season to season. Sometimes one feels almost as inert as if he lived within the tropics, but soon a change comes and one again feels the health and energy which make it possible to work hard and think clearly.
How People's Health and Energy are Measured.—There are many ways of measuring the variations in the health and energy of a community from season to season. People's energy can be measured by studying what they accomplish in cases where they do the same thing day after day as among piece workers in factories. Again, a good measure of the energy of individuals is found in the test ing apparatus used in gymnasiums. Or the health of children, for instance, can be measured by recording their rate of growth in height and weight. The health of the whole community can be measured by the number of deaths from disease. Or again the health and energy of the mind can be measured by finding out the difference from week to week in the work done by school children, bank clerks, or other people whose occupations demand brain work. All these
ways of measurement, as well as many others, lead to the same con clusion. In a variable climate such as that of the United States people's health and energy go through a regular series of changes each year.
The Way in Which People's Physical Energy Varies from Season to Season.—The variations in people's strength from month to month are so important and teach so much about the distribution of health and energy throughout the world that we may well study them closely. Let us consider first how physical strength varies during the course of the year in the great section extending from southern New England and New York westward to the Rocky Mountains. October is usually the best month. At that time people feel like working hard; they get up in the morning full of energy, and go at their work quickly and without hesitation; they walk briskly to business or work; and play with equal vigor. Headaches, colds, indigestion, and other minor illnesses are fewer than at other seasons; there are also fewer serious illnesses, so that the doctors have less than usual to do, and the number of deaths is less than at any other time of year.
Then as cold weather comes on, the workers accomplish less, ill health becomes more and more common, the physicians are kept busy, and deaths increase. By January or February the general efficiency and health may have dropped 20 or 30 per cent. In a cold winter these bad conditions may last through March, but ordinarily there is an improvement as soon as the air begins to become warmer. The improvement continues through the spring until in May or early June the conditions of health and energy are almost as good as in October. Then with the arrival of hot weather an unfavorable change begins. By the middle of July people's health and energy are often no better than in January and may be worse. The diseases are not quite the same as in the winter, since stomach troubles, for instance, are more common than colds. Moreover, the feeling of laziness that comes over people in hot weather is not quite the same as the sort of suffocating stupid feeling that one has in winter. Yet the effect on work and health, and the result in low efficiency and many deaths are the same.