Sir Joseph John Thomson ‎(‎1856‎-1940‎)‎ was a British physicist who is credited with the discovery of the electron‎.‎ First published in 1933‎,‎ this volume is one of two books making up the third edition of a 1903 original by Thomson‎.‎ The text was greatly enlarged for this edition‎,‎ which resulted in its division into two parts‎,‎ and incorporates numerous advances in research relating to the discharge of electricity through gases‎.‎ Numerous illustrative figures are provided throughout‎.‎ This book will be of value to anyone with an interest in Thomson and his contribution to the development of physics‎.‎