By E. Cartmell and G. W. A. Fowles London: Butterworths Scientific Publications. Pp. 256 + xi. Price 32s. 6d. The quantum theory is fundamental for the development of modern theories of valency and molecular structure, and because of the overwhelming importance of the valency concept in chemistry many teachers nowadays are of the opinion that, in spite of the pedagogic difficulties, a student should be introduced to wavemechanics and some of its simpler chemical applications quite early in his university course. The average student of chemistry is not equipped, in his earlier years at least, to read the standard works on wavemechanics; the work under review is one of the latest of many attempts to present the subject to him in a (mathematically) less formidable guise.