In the “Principles of Human Geography”, it is stated that “in Central France and Southern Germany the seasonal variations in health and strength are much the same as in Boston, New York, Cleveland, and Detroit. That is, people are most healthy and strong in October and early November and again in May and early June, while they are weakest and most subject to disease in January, February, and early March, and again in July and August. Farther north, for example, in Scotland, Scandinavia, and Finland, the summer is the best time of the whole year and the winter the worst. To the south, on the contrary, in Italy, Spain, and Greece, the harmful effect of the winter decreases and that of summer increases, until finally on the south side of the Mediterranean the winter is much the best time of the whole year, while the long summer greatly diminishes the people’s efficiency and increases disease and death.” As the highest mental activity is coincident with temperatures lower than those that induce the greatest physical energy, it naturally follows that in the Ohio Valley, southern New England, and the Middle Atlantic States the mental worker is at his maximum in November instead of October, and April instead of May. [Illustration: CHART 17.—MAP OF CLIMATIC ENERGY. (Huntington and Cushing.)] Chart 17 shows how human energy would be distributed over the earth if it depended on climate alone. It is remarkable how almost exactly it agrees with what we know to be the distribution of the great political power. Japan is meant to be included in the region of high power, but the scale of the chart is too small to make this plain. [Illustration: CHART 18.—DENSITY OF POPULATION IN THE UNITED STATES, 1910.]