A radiation of frequency v has to be considered as divided into atoms of light of very small internal mass (-io~50 gm.) which move with a velocity very nearly equal to c given by -=2=^=to. The atom *J i - p of light slides slowly upon the non-material wave the frequency of which is v and velocity c/p, very little higher than c.

The “phase wave “has a very great importance in determining the motion of any moving body, and I have been able to show that the stability conditions of the trajectories in Bohr’s atom express that the wave is tuned with the length of the closed path.

The path of a luminous atom is no longer straight when this atom crosses a narrow opening; that is, diffraction. It is then necessary to give up the inertia principle, and we must suppose that any moving body follows always the ray of its “phase wave “; its path will then bend by passing through a.sufficiently small aperture. Dynamics must undergo the same evolution that optics has undergone when undulations took the place of purely geometrical optics. Hypotheses based upon those of the wave theory allowed us to explain interferences and diffraction fringes. By means of these new ideas, it will probably be possible to reconcile also diffusion. and dispersion with the discontinuity of light, and to solve almost all the problems brought up by quanta.