This proof that the α-particles consisted of actual charged atoms of matter projected with an enormous velocity at once threw a flood of light on radioactive processes, in particular upon another important series of investigations which were being contemporaneously carried on in the Laboratory at Montreal in conjunction with Mr. F. Soddy. Had time permitted, it would have been of interest to consider in some detail the nature of these researches which placed on a firm foundation the now generally accepted "transformation theory" of radioactivity. From a close examination of the substances thorium, radium, and uranium, Rutherford and Soddy had reached the conclusion that radioactive bodies were in a state of transformation, as a result of which a number of new substances were produced entirely distinct in chemical and physical character from the parent element. From the independence of the rate of transformation of chemical and physical agencies, it was recognized that the transformation was atomic and not molecular in character. Each of these new bodies was shown to lose its radioactive properties according to a definite law. Even before the discovery of the material nature of the α-rays, it had been considered probable that the radiation from any particular substance accompanied the breaking up of its atoms. The proof that the α-particle was an ejected atom of matter at once strengthened this conclusion and at the same time gave a more concrete and definite representation of the processes occurring in radioactive matter. The point of view reached by us at that time is clearly seen from the following quotation, which with little alteration holds good today. "The results obtained so far point to the conclusion that the beginning of the succession of chemical changes taking place in radioactive bodies is due to the emission of the α-rays, i.e. the projection of a heavy charged mass from the atom. The portion left behind is unstable, undergoing further chemical changes which are again accompanied by the emission of α-rays, and in some cases also of β-rays. "The power possessed by the radioactive bodies of apparently spontaneously projecting large masses with enormous velocities supports the view that the atoms of these substances are made up, in part at least, of rapidly rotating or oscillating systems of heavy charged bodies, large compared with the electron. The sudden escape of these masses from their orbit may be due either to the action of internal forces or external forces of which we have at present no knowledge."[2]