The absolute synchronism exhibited under all amplitudes of vibration by the disk-atom indicates the same law of central force as that of the pendulum in its synchronous forms, or the spring-governor; and if attraction be the bond, it is a similar law of attraction, namely, directly as the distance. This is the Newtonian law of gravity within the homogeneous sphere, and thus by actual demonstration the attractive atom observes the same law as would the earth were it penetrable—namely, the inverse squares of the distances within the sphere.
The identity of the radiant particle with the component of the atom is inferable. It possesses the requisite properties of mass and resilience, and sufficient linear motion. Whether it should also have attraction imputed to it as inherent depends on whether that property in the molecule, where alone it is observed, is derived from the particle. If not, the latter needs only mass to conserve its deflections and its course under the first law of motion, and resilience to secure its compensatory readjustment in equilibrium. Even if possessed of gravity, the enormous proper velocity of the particle would render such an affection totally undiscoverable, because the Newtonian curves of the second order resulting from the composition of force could be nothing less than hyperbolas, whose branches would be wholly undistinguishable from straight lines.
No means at present offer themselves for suggesting how such a discontinuity of action as is implied by the change from simple linear motion to the balanced movements of the atoms could have occurred; and especially how a law of attraction according to inverse squares of distance, which we must postulate, could change for one so extraordinary as that observed within the atom, namely, directly at the distance. The law referred to rather resembles that of our summer whirlwinds, wherein the centripetal force, i. e., the pressure from without due to the rarefaction within, seems to vary directly as the centrifugal force, and therefore as the radius, until equilibrium of rotation is established. These also display a species of attraction within the vortex; and some forms of matter—as iron—evince a similar polar attraction at sensible distances when rearranged by vortical motion. But such a theory does not commend itself by that simplicity which we should expect in the region of the atom.
The evolution of the atom or elementary molecule from the particle, even if real, is not continuous with the present order of nature within our observation, and need not be, any more than the formation
- This parallel holds good only for the balanced couples themselves, in which I have assumed the cause of the stress to reside. The intensity of the stress would not vary as the distance from the center for a third body, as in the permeable sphere, but the field would be like a strained elastic tympanum, with varying tension dependent on the separation of the elements. The mathematical discussion of this field of force would be most interesting, involving, as it does, the investigation of all the phenomena of refraction and reflexion.