Page:Popular Science Monthly Volume 67.djvu/11



INCE the initial discovery by Becquerel of the spontaneous emission of new types of radiation from uranium, our knowledge of the phenomena exhibited by uranium and the other radioactive bodies has grown with great and ever increasing rapidity, and a very large mass of experimental facts has now been accumulated. It would be impossible within the limits of this article to review even briefly the more important experimental facts connected with the subject and, in addition, such a review is rendered unnecessary by the recent publication of several treatises in which the main facts of radioactivity have been dealt with in a fairly complete manner.

In the present article an attempt will be made to discuss the more important problems that have arisen during the development of the subject and to indicate what, in the opinion of the writer, are the subjects which will call for further investigation in the immediate future.

The characteristic radiations from the radioactive bodies are very complex, and a large amount of investigation has been necessary to