O. Hahn. What Does Radioactivity Teach Us About the History of the Earth? Pp. IV + 64. Verlag von J. Springer. Berlin, 1926.

O. Hahn. What does radioactivity teach us about the history of the Earth?

This small book is an expanded exposition of a lecture delivered by the author at a public session of the Prussian Academy of Sciences in November 1925. The author rightly notes that the highly interesting questions forming the subject of his lecture have until now received far too little attention in broad circles. These questions fall into two large groups: 1. the determination of the age of the Earth by radioactive methods, and 2. the problem of the Earth’s heat balance. Both groups of questions are treated with sufficient completeness in the book under review. Especially interesting are Chapters III and IV, which are devoted to the role of radioactivity in the Earth’s heat balance and to Joly’s fascinating theory concerning rhythmic changes of the Earth’s crust under the influence of the heat of radioactive decay.

The booklet is intended for a broad readership and is written in an exceptionally easy and engaging manner.

É. Shpolsky.