General Meeting- April 18-20, 1929 The Annual General Meeting of The American Philosophical Society will be held on April 18th, 19th, and 20th, 1929, beginning at 2 P.M. on Thursday, April 18th. Members are requested to send to the Secretaries, at as early a date as practicable and before March 1, 1929, the titles of papers which they intend to present so that they may be announced in the preliminary programme which will be issued as soon as possible after that date and which will give in detail the arrangements for the Meeting. It is understood that papers offered are original contributions which have not been theretofore presented. All papers presented which are favorably acted on by the Publication Committee will, in accordance with the rules of the Society, be published as soon as practicable in either the Proceedings or the Transactions as may seem best. ARTHUR W. GOODSPEED Secretaries Members who have not as yet sent their photographs to the Society will confer a favor by so doing; cabinet size preferred. It is requested that all correspondence be addressed TO THE SECRETARIES OF THE AMERICAN PHILOSOPHICAL SOCIETY 104 SOUTH FIFTH STREET PHILADELPHIA, U. S. A. DISCUSSION OF THE KINETIC THEORY OF GRAVITATION By CHARLES F. BRUSH (Read April 21, 1928) AT THE Minneapolis meeting of the American Association for the Advancement of Science in December 1910, I had the honor to outline "A Kinetic Theory of Gravitation." This was followed by a "Discussion" of the theory in 1914.2 A second "Discussion" came in 1921.3 A third "Discussion" appeared in 1926.4 The latter paper contains a concise synopsis of the theory, and strong argument supporting my contention of 1910, that the energy acquired by falling bodies is derived from the ether. This third "Discussion" (1926) contains in its title "Some Experimental Evidence Supporting Theory; Continual Generation of Heat in Some Igneous Rocks and Minerals. Relation of This to the Internal Heat of the Earth and Presumably of the Sun." Quoting from this paper: "Gravitation Waves and Heat. "Heat is often defined as an agitation of atoms and molecules of matter, and measured by the total kinetic energy of such agitation. The agitation consists partly in internal vibrations of the elastic atoms and molecules and spinning about their various axes, and partly in a very rapid translatory motion among themselves. Thus they are sup 1 Science, March 10, 1911; Nature, March 23, 1911. 2 Proc. Am. Phil. Soc., Vol. LIII, No. 213, January-May 1914. 3 Proc. Am. Phil. Soc., Vol. LX, No. 2, 1921. 4 Proc. Am. Phil. Soc., Vol. LXV, No. 3, 1926. posed to dart about in every conceivable direction, constantly colliding with each other and rebounding or glancing in new directions. The kinetic energy of this translatory motion constitutes sensible heat (not total heat) and is the measure of temperature. Anything (such as absorbed radiation) which stimulates the internal vibration of atoms or molecules likewise increases their translatory velocities by the increased violence of rebound after collision, and thus increases their temperature; and vice versa. "All the above is known to be true of gases and vapors (kinetic theory of gases), and is generally believed to be true of liquids and solids. "The mean free path' and the 'mean velocity' between collisions of the molecules of many gases under stated conditions have been computed. But it has also been shown mathematically that the higher and lower velocities, and the longer and shorter paths, differ greatly from the means, and may in each respect vary twenty or more times in amount. Doubtless this is true also of liquids and solids. "Certainly the 'free path' of atoms and molecules in solids must be very short, but quite as certainly there must be some space for movement because we know that the atoms or molecules of solids are not in contact. And diffusion of contiguous metals into each other proves migration of the atoms or molecules just as in gases, though vastly slower, as we should expect from the extreme shortness of their free paths. "From the fortuitously wide variation in velocities and free paths of the billions of vibrating atoms or molecules in their heterogeneous movement, it follows that collision frequencies must also vary greatly, from instant to instant, everywhere in a body of matter. "Probably the postulated gravitation waves are not confined to one frequency, but have a wide range of frequencies as do the well-known X-rays. "With the foregoing in mind it is easily conceivable that some kinds of matter may have atoms or simple molecules or complex molecules of occasional vibration frequency corresponding with some gravitation wave frequency, whereby fortuitous resonance can, for brief instants, be established at various points. This would result in a slight increase of vibrational activity and a cumulative rise of general temperature, perhaps sufficient to be detected. "A body of such matter, with some thermal insulation, would become and remain permanently warmer than a neighboring body similarly circumstanced, but not endowed, or less endowed with the permissive heat-generating quality." The foregoing hypothesis had been my guide in a very lengthy search for some material exhibiting continual generation of heat in observable amount. A carefully designed calorimeter is illustrated and described in the paper (1926), and details of many experiments given. These resulted in the discovery that some rocks and minerals did.generate an easily observable amount of heat. But in some instances this declined materially in the next few months. The cause of the decline, or rather the cause of the abnormally large generation of heat in recently crushed minerals, has been ascertained, and is referred to in this and the succeeding paper (1927). In April 1927 I presented another paper on "Persistent Generation of Heat in Some Rocks and Minerals." This is a continuation of the 1926 paper. It describes a new and different calorimeter, built in the spring of 1926, and since known as the "Ice Calorimeter." It has been in almost continuous use down to the present time (April 1928) and has proved very satisfactory. With this calorimeter it has been found that some of the natural heat-generating materials, and some of the artificial silicates hereafter described, have retained their heat-generating activity unimpaired; and none of these substances is more than minutely radioactive. Quoting from the 1927 paper: "It is notable that all the materials which appear to be endowed with persistent heat generating activity are very 1 Proc. Am. Phil. Soc., Vol. LXVI, 1927. |