15 JANUARY 1921, Page 20

The Foundations of Chemical Theory. . By R. M. Caven. (Blackie.

12s. 6d. net.)—Professor Caven's clear exposition of modern chemical theory, though mainly intended for use as a text-book, will interest laymen who have not followed the developments of chemistry with close attention. Unlike the ordinary treatise, the book seeks to emphasize general principles rather than to record a mass of facts.