On some Dynamical Conditions applicable to Le Sage's Theory of Gravitation. Samuel Tolver Preston

and was dissipated again in ultramundane space—a means apparently quite disproportionate to the end in view. We observe that under the principles of the kinetic theory no such supply is necessary, but that all the conditions requisite for gravity may be fulfilled by a medium pervading the visible universe, and which is at rest as a whole ; or the gravific medium within the bounds of the visible universe may be compared to the air within a receptacle, which is, as a whole, at rest; and therefore there is no more waste of the matter producing gravity than if mundane matter did not exist. If we imagine, in analogy, a being extremely small compared with the mean length of path of an air molecule, to be stationed in the centre of a receptacle containing air ; then this minute observer would notice the air molecules passing continually in streams equally in all directions ; and the observer, not being able to trace the beginning and end of the path of the molecules, would naturally imagine that the molecules were being supplied in streams from outside the receptacle, and, observing the continued regularity of the streams equally in all directions, would suppose that there must be some external mechanism supplying the streams of molecules equally and symmetrically. This is what would be supposed in the absence of the application of the principles of the kinetic theory to the case. On applying this theory, it is seen that the same result can take place without a supply of air ; and that the adjustment of the streams of air molecules uniformly in all directions is automatic, or the inevitable result of dynamical principles.

      3 ↑ If two particles of a gas be conceived gradually to increase in size and mass, they will gradually lose their translatory motion and finally come practically to rest. If now the two enlarged particles be at a distance apart less than the mean length of path of the remaining particles of the gas, these two particles will gravitate towards each other under the dynamic action of the other particles of the gas which pass them in streams (the opposed faces of the two enlarged particles being sheltered from the streams). This condition of things probably occurs when a vapour condenses, when the gradually enlarging water vesicles which happen to be at a distance apart less than the mean length of path of the other molecules of the vapour will be driven together by the dynamic action of these molecules, thus accelerating condensation. Thus possibly effects of "gravity" may be imitated by gaseous matter on molecular scale, as is observed in the large scale of the universe. It may be observed that these are simply applications on a smaller scale of the dynamical principles of Le Sage's theory, and therefore the deductions hold if the premises are admitted to be possible.