IN contrast to a recent paper by Hunter and Samuel1, which has been criticised even more adversely by physicists than by chemists2, Prof. Hunter's book on "The Electronic Theory of Chemistry" is a trustworthy guide to modern views on the theory of valency, since it is very largely descriptive in character, and is more concerned with chemical facts than with physical theories. The chief fault that can be attributed to the book is a lack of historical perspective, which gives to it a flavour of immaturity.