138 SCIENCE PROGRESS 



plan will be found advantageous in classes where various students may 

 have the two editions in use at the same time. 



Prof. Love's treatise is so well known that detailed comment on its con- 

 tents is not necessary. The science of elasticity has so many applications, 

 both in physics and in engineering, that so complete an account of it as is 

 given by Prof. Love is invaluable, not merely as a textbook, but as a stan- 

 dard work of reference. Detailed references to the original authorities are 

 given throughout which will enable students who may desire to pursue any 

 particular matter further to find the relevant literature. Standard works, 

 to retain fully their value, must be kept up-to-date, and it is a matter for 

 general satisfaction that Prof. Love has found it possible to bring out the 

 present third edition. 



H. S. J. 



ASTRONOMY 



The Foundations of Einstein's Theory of Gravitation. By Erwin Freund- 

 LiCH. Authorised English Translation by Henry L. Brose, M.A. 

 Preface by Albert Einstein. Introduction by H. H. Turner, 

 D.Sc, F.R.S. [Pp. xvi + 62.] (Cambridge : at the University 

 Press, 1920. Price 5s. net.) 



Mr. Brose became interested in Einstein's Theory of Gravitation whilst 

 interned in Germany as a civilian prisoner of war, and there made his trans- 

 lation of Dr. Freundlich's booklet dealing with the foundations of the 

 theory. Dr. Freundlich, of the Berlin Observatory, was the first scientist 

 to endeavour to put the theory to the test : he had planned to take photo- 

 graphs during the total solar eclipse of August 1914, with a view to deter- 

 mining the amount, if any, of the deflections of light rays by the sun's 

 gravitational field. The outbreak of war prevented him carrying out his 

 plans. It is evident, therefore, that he has been interested in the theory 

 from its inception. 



His exposition of the fundamental ideas underlying the theory is the 

 best that we have yet seen. He has explained in a very clear manner the 

 two fundamental postulates of continuity and of causal relationship between 

 such things as lie within the realm of observation, and has shown that the 

 principles of classical mechanics cannot be brought into accord with these 

 postulates. It is then shown how Einstein built his theory around this 

 framework. The relationship of the theory to the ideas of Riemann is 

 particularly well brought out. The mathematical development of the 

 theory is sketched but without introducing analysis, so that the volume 

 will be found intelhgible to all who are conversant with the methods of 

 reasoning of the exact sciences. 



The principal criticism of the work as an exposition of Einstein's theory 

 is that the exact meaning of the interpretation of the fundamental prin- 

 ciple of equivalence and of the assumptions involved in it is only very briefly 

 dealt with. It is a difficult matter, however, to discuss the limitations of 

 the principle without introducing the mathematics of the theory. 



The present translation has been perused by Dr. Freundlich himself, so 

 that its accuracy can be admitted. Mr. Brose deserves the thanks of scien- 

 ■ tists in general for making this exposition accessible to English readers. 



H. S. J. 



CHEMISTRY 



Alcohol : Its Production, Properties, Chemistry, and Industrial Applications. 



By C. Simmonds, B.Sc. [Pp. xx -f 574, with numerous illustrations 

 and diagrams.] (London: Macmillan & Co., 1919. Price 21s. net.) 



Mr. Simmonds's excellent volume on Alcohol has appeared at a very oppor- 

 tune moment, for not only is the eternal controversy between " The Trade " 



