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Rh called forth many relationships between it and the social sciences. What it has done in explaining the exhaustion, what it has contributed to the understanding of the significance of the forest covering for climate and for the cultivation of field and garden vegetation has benefited the social sciences. But there are besides many other relations existing between these two seemingly widely separated sciences. In order further to illustrate this I will give another example, intentionally an extreme but instructive case. For almost a century men busied themselves with the question as to how long the earth's stores of coal would last in view of the enormous increase in the use of fuel. The estimates awakened grave apprehensions, though one might reassure himself by this fact that the premises upon which such dire conclusions were based lacked very much of being accurate. Next, comes from across the ocean a more disturbing and vexatious intelligence. Through the American and English papers goes the news—reflected also in the German press—that the danger of extinction of mankind would come sooner than had hitherto been feared. Under an appeal to the authority of a great physicist it was claimed that, with the increasing consumption of mineral fuel by the various industries, all supplies of mineral coal would be exhausted within five hundred years. But the last remnants of coal—so it was further claimed—it would no longer be possible to bring out of the earth, because in the meantime the oxygen of the atmosphere, as a result of the enormous increase in combustion, would have decreased to such a limit that the air would no longer be adapted for human respiration.

The computations in question seemed to be entirely accurate, but again the assumptions were uncertain, upon which these terrible results were predicted, as indeed the whole question whose solution proceeded upon complications of a similar kind, were dealt with only from the chemical standpoint, quite disregarding the character of living organisms.

Every condition of the earth which corresponds with the Kant- Laplace theory forms the starting point for computations like those above cited. All of the earth's carbon is burned up; all of the oxygen allotted to our planet is exhausted. After cooling of the earth, the green vegetation appears and generates free oxygen under the influence of sunlight. This hypothesis derives the whole of the atmospheric oxygen from the green vegetation. Since, at that time, there was no other natural source of oxygen upon the earth besides the green plants, it followed that with increasing combustion the oxygen supply would diminish. In order to check this decrease it was advised that extensive areas of fruit trees should be planted. So it was hoped that in this way a sufficient quantity of oxygen and human sustenance would be assured to help out the inhabitants of the earth. What small agencies opposed to the harmonious working of the powers of nature!

Upon how weak a foundation the foregoing hypothesis stands may