SECOND EDITION

CAMBRIDGE

AT THE UNIVERSITY PRESS

1905

First Edition 1904

Second Edition 1905

J. J. THOMSON

A TRIBUTE OF MY RESPECT AND ADMIRATION

PREFACE TO THE FIRST EDITION.

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. Although the subject is comparatively a new one, our knowledge of the properties of the radio-active substances has advanced with great rapidity, and there is now a very large amount of information on the subject scattered throughout the various scientific journals.