REVIEWS 149 



the chemical equivalent weight of an ion in electrolysis 95706 instead of 

 96470. 



The printing and paper in the new edition are the same as in the first ; 

 it is to be regretted that the publishers find it necessary to make the price 

 so much greater. 



D. O. W. 



The Dynamical Theory o£ Gases. Third Edition. By J. H. Jeans, M.A., 

 F.R.S., formerly Stokes Lecturer in Applied Mathematics in the 

 University of Cambridge ; sometime Professor of Applied Mathematics 

 in Princeton University. [Pp. vi + 442.] (Cambridge : at the 

 University Press, 1921. Price 305. net.) 



The Mathematical Theory of Electricity and Magnetism. Fourth Edition. 

 By J. H. Jeans, M.A., F.R.S. [Pp. vi + 627.] (Cambridge : at 

 the University Press, 1920. Price 24s. net.) 



We welcome the third edition of Mr. Jeans's book on The Dynamical Theory 

 of Gases and the fourth edition of his Mathematical Theory of Electricity and 

 Magnetism. To the first the author has added an entirely new chapter on 

 Quantum Dynamics, incorporating the recent work of Ehrenfest, Sommerfeld, 

 and Epstein ; he has, further, enlarged and rewritten the chapter on Radiation 

 and the Quantum Theory, which appeared in the second edition. The fourth 

 edition of Electricity and Magnetism differs from its predecessors principally 

 in the addition of a wholly new chapter on the Theory of Relativity. 



It is not necessary to say anything to recommend either of these books. 

 The fame of the author as a brilliant and clear expositor is as widespread 

 as his reputation as a penetrating and wonderful thinker in mathematical 

 physics. 



D. M. Wrinch. 



CHEMISTRY 



The Experimental Basis of Chemistry. By Ida Freund. Edited by 

 A. Hutchinson and M. Beatrice Thomas. [Pp. xvi + 408. J (Cam- 

 bridge : at the University Press, 1920. Price 30s. net.) 



In Miss Ida Freund the teaching of elementary chemistry has lost one of 

 its most able exponents. The teaching of elementary chemistry — that is, 

 the fimdamental principles of chemistry; the term "elementary" is too often 

 taken to be synonymous with "easy" — has in England never received the 

 attention it deserves from the leaders of chemical thought. They have been 

 content to leave to the pedagogue the application of modern methods of 

 teaching to the exposition of the subject, and, owing to lack of appreciation 

 of scientific method, the best results have not always been obtained. Miss 

 Freund was not only an enthusiastic educationist, but possessed that keen 

 critical faculty and sound knowledge of scientific principles which caused 

 her to revolt against some of the irrational ideas of the heuristic method 

 of teaching science, and teachers of chemistry are fortunate in having her 

 views so clearly expressed in the present volume. 



The book, founded on a laboratory course, as the editors explain in their 

 Preface, is the result of a desire on the part of Miss Freund " to bring to the 

 notice of other teachers her views as to the manner in which students might 

 be helped to realise that chemistry is a science based on experiment, and 

 that the logical interpretation of experiment leads directly to the generalisa- 

 tions known as the laws of chemistry." Unfortunately, the author's death 

 left it incomplete, but the more important part was at that time almost 

 ready for the press, and, being complete in itself, is now published under the 

 editorship of two of the author's personal friends. 



