“The last thing to be considered in Figure 8 [p. 99] is the mental curve [showing optimum mental work at 38° F.] at the bottom. It is based on so large a number of people, and is so regular, that its general reliability seems great, although I think that future studies may show the optimum to be a few degrees higher than is here indicated. It agrees with the results of Lehmann and Pedersen. Furthermore, from general observation we are most of us aware that we are mentally more active in comparatively cool weather. Perhaps ‘spring fever’ is a mental state far more than a physical. Apparently people do the best mental work on days when the thermometer ranges from freezing to about 50°—that is, when the mean temperature is not far from 40°. Inasmuch as human progress depends upon a coördination of mental and physical activity, we seem to be justified in the conclusion that the greatest total efficiency occurs halfway between the mental and physical optima, that is, with a mean temperature of about 50°” (pp. 102–103).
The curves (p. 105) on Mean Temperature and Vital Processes in Plants, Animals and Man show physical energy to be at the optimum at the mean temperature of 60° F., mental energy at 38°, mental and physical energy combined at from 40° to 60°. Of this last mentioned curve he says: “It may be taken as representing man’s actual productive activity in the things that make for a high civilization. The resemblance of the human curves to those of the lower organisms is obvious. In general, the lower types of life, or the lower forms of activity, seem to reach their optima at higher temperatures than do the more advanced types and the more lofty functions such as mentality. The whole trend of biological thought is toward the conclusion that the same laws apply to all forms of life. They differ in application, but not in principle. The law of optimum temperature apparently controls the phenomena of life from the lowest activities of protoplasm to the highest activities of the human intellect” (pp. 109–110).
In Chapter VI (“Work and Weather,” pp. 111–128), he interprets the curves he plotted showing especially the influence of changes of temperature from day to day, and of the character of each day and its relation to storms. In the very interesting Chapter VII (pp. 129–147) he discusses “The Ideal Climate.”
In the closing paragraph of his book, he says, “If our hypothesis is true, man is more closely dependent upon nature than he has realized. A realization of his limitations, however, is the first step toward freedom [p. 293].
“The hypothesis, briefly stated, is this: Today a certain peculiar type of climate prevails wherever civilization is high. In the past the same type seems to have prevailed wherever a great civilization arose. Therefore, such a climate seems to be a necessary condition of great progress. It is not the cause of civilization, for that lies infinitely deeper. Nor is it the only, or the most important condition. It is merely one of several, ...” (p. 9.)
Huntington mentions (p. 7) Lehmann and Pedersen’s “Das Wetter und unsere Arbeit” and Berliner’s “Einfluß von Klima, Wetter und Jahreßeit auf das Nerven- und Seelenleben,” without the date or place of publication.
Note: Since the foregoing pages went to press, the following publications have appeared; being too late for inclusion or comment in the text, they are added here for reference:
Douglas W. Johnson, Topography and Strategy in the War, N. Y., Henry Holt & Co., 1917, 221 pp. (Thorough and very illuminating; points out how the surface features of the country influenced military operations in the most important theaters of the war.)
James Fairgrieve, Geography and World Power, N. Y., E. P. Dutton & Co., 1917, 356 pp. (Shows how History has been controlled by Geography.)
Robert De C. Ward, “Weather Controls Over the Fighting in the Italian War Zone,” The Scientific Monthly, Vol. 6, No. 2 (February, 1918), pp. 97–105. And “Weather Controls Over the Fighting in Mesopotamia, in Palestine, and near the Suez Canal,” ibidem, Vol. 6, No. 4 (April, 1918), pp. 289–304.