In this work, I have endeavoured to give a complete and connected account, from a physical standpoint, of the properties possessed by the naturally radio-active bodies. I have found the theory that the atoms of the radio-active bodies are undergoing spontaneous disintegration extremely serviceable, not only in correlating the known phenomena, but also in suggesting new lines of research.

The present edition includes a large amount of new material relating to the nature and properties of the radiations and the emanations. In the limits of this book, it would have been found impossible, even had it been thought desirable, to include more than a brief sketch of the physiological effects of the rays.

(E. RUTHERFORD - 1905)