Kinetic Theories of Gravitation/Boisbaudran, 1869
Another short paper, entitled a "Note on the Theory of Weight," was presented to the Academy September 20, 1869, by M. Lecoq de Boisbaudran, called forth by the previous communication of M. Leray. He remarks: "Having been myself occupied on this question, I have the honor to communicate to the Academy the actual state of my researches. On certain points, and particularly on the explanation of the central, heat of the stars, I am happy to agree with M. Leray ; on other points my conclusions differ from his. I attribute to matter, whatever may be its state of division, no other essential properties than those established by experimental physics and mechanics. I designate as atoms the last stage of division of matter. I admit that two bodies separated by an absolute void cannot act on each other ; that action takes place only by contact, the play of forces following the laws of ordinary mechanics. If there existed but a single kind of atoms, the interchange of forces occurring between equal masses, two atoms could not unite. Force and matter would exist, but not attraction. There are then at least two kinds of primordial atoms of different masses. The smaller may be called aether ; the others, ponderable atoms." The writer then goes on to say that a ponderable atom in the midst of a vibrating aether would itself receive a vibration (though of less activity than that of the aether) without being displaced in space, the portion of energy lost by the aether being transformed into heat, etc. A second atom being placed near the first, the aether vibrations would be feebler between the two than in exterior space, which would result in approach.
" I prefer the notion of vibrations of the aether to that of "equal currents crossing each other in all directions." The attraction exerted on  a ponderable atom is cot in the simple ratio of its mass; for if this mass equalled that of an aether atom, the attraction would be nil. If there exist ponderable atoms of different masses their rate of fall would be unequal. If there were but one kind of ponderable atom, all bodies would fall with equal velocity. Experience seems to justify the last hypothesis, but very slight differences of mass in the ponderable atoms would suffice to determine the formation of chemical elements of very different atomic weights, and an inequality of their fall would escape unadvised observers.
After affirming the law of distance, M. Boisbaudran says : " In consequence of the inertia of the aether, attraction is not proportional to the real masses, but no more is it to the number of ponderable atoms contained in a body. The vis viva of the atoms of aether, however great, has a finite value." Lastly, he remarks : " It is to the longitudinal vibrations of the aether that I attribute the cause of weight."
Neither the hypothesis of M. Leray, nor that of M. Boisbaudran, presents any feature of special novelty, requiring comment.
- Comptes Rendus, 20th September, 1869, vol. lxix, pp. 703,704.