bodies themselves, seem quite without influence on the disintegration of the radio-active elements. The bombardment by α rays seems to be the most promising means of producing atomic transformation, for in this case the energy of the rays comes from these transformations themselves—''tis its own pinion that impels the steel.' They do not, however, appear to produce any appreciable effect, for the life of a radio-active substance in a dilute solution, where it is only exposed to a few α rays, seems to be no longer than the life in a strong solution, where the substance is bombarded by many rays. I have made many experiments to see if I could split up atoms of one kind into those of another by exposing them to electric discharges, bombardment by cathode or positive rays, and other agents; using the very sensitive method of positive ray analysis to detect the formation of any disintegration products; this method can detect less than a millionth of a cubic centimetre of a gas at atmospheric pressure. By these means I have been able to disintegrate the atoms to the extent that I could split off from them some of the electrons they contained; from the atom of mercury, for example, I have been able to detach eight electrons, from hydrogen one electron, the only one it had. I have never, however, been able to get any evidence that I regard as at all conclusive that the atom of one element could by such means be changed into an atom of a different kind; in other words, that by such means we could produce a transmutation of the elements.
Ratio of Mass to Weight
We have seen that the view, so strongly supported by recent experiments, that the atoms of the elements are aggregations of simpler systems, involves the admission