Note 40 — Chapter IX · CATHODE RAYS AND RADIOACTIVE BODIES
Reading edition
This opinion, no doubt formed when Sir William Ramsay's discovery of the formation of helium from the radium emanation was first made known, is now less tenable. The latest theory is that the alpha particle is in fact an atom of helium, and that the final transformation product of radium and the other radioactive substances is lead. Cf. Rutherford, op. cit. passim.—ED.