much greater degree in the past, or be destined to do so in the future. Thus an electrical hypothesis of solar disturbances seems to indicate that the position of the sun in respect to other stars may be a factor of great importance in determining the earth's climate. FOOTNOTES: [Footnote 112: H. H. Turner: On a Long Period in Chinese Earthquake Records; Mon. Not. Royal Astron. Soc., Vol. 79, 1919, pp. 531-539; Vol. 80, 1920, pp. 617-619; Long Period Terms in the Growth of Trees; _idem_, pp.793-808.] [Footnote 113: Harlow Shapley: Note on a Possible Factor in Geologic Climates; Jour. Geol., Vol. 29, No. 4, May, 1921; Novae and Variable Stars, Pub. Astron. Soc. Pac., No. 194, Aug., 1921.] [Footnote 114: J. H. Jeans: Problems of Cosmogony and Stellar Dynamics, Cambridge, 1919.] [Footnote 115: This fact is so important and at the same time so surprising to the layman, that a quotation from The Electron Theory of Matter by O. W. Richardson, 1914, pp. 326 and 334 is here added. "It is a very familiar fact that when material bodies are heated they emit electromagnetic radiations, in the form of thermal, luminous, and actinic rays, in appreciable quantities. Such an effect is a natural consequence of the electron and kinetic theories of matter. On the kinetic theory, temperature is a measure of the violence of the motion of the ultimate particles; and we have seen that on the electron theory, electromagnetic radiation is a consequence of their acceleration. The calculation of this emission from the standpoint of the electron theory alone is a very complex problem which takes us deeply into the structure of matter and which has probably not yet been satisfactorily resolved. Fortunately, we can find out a great deal about these phenomena by the application of general principles like the conservation of energy and the second law of thermodynamics without considering special assumptions about the ultimate constitution of matter. It is to be borne in mind that the emission under consideration occurs at all temperatures although it is more marked the higher the temperature.... The energy per unit volume, _in vacuo_, of the radiation in equilibrium in an enclosure at the absolute temperature, T, is equal to a universal constant, A, multiplied by the fourth power of the absolute temperature. Since the intensity of the radiation is equal to the energy per unit volume multiplied by the velocity of light, it follows that the former must also be proportional to the fourth power of the absolute temperature. Moreover, if E is the total emission from unit area of a perfectly black body, we see from p. 330 that E=A'T^{4}, where A' is a new universal constant. This result is usually known as Stefan's Law. It was suggested by Stefan in the inaccurate form that the total radiant energy of emission from bodies varies as the fourth power of the absolute temperature, as a generalization from the results of experiments. The