NA rURE 



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THURSDAY, DECEMBER lo, 1914. 



RELATIVITY. 

 The Theory of Relativity. By Dr. L. Silberstein. 

 Pp. viii + 295. (London: Macmillan and Co., 

 Ltd., 1914.) Price los. net. 



THE appearance of a connected account of 

 the Principle of Relativity in our own lan- 

 guage will be welcomed by many as an oppor- 

 tunity of acquainting themselves in more detail 

 with the ins and outs of a controversial subject. 

 The note of controversy is, however, almost com- 

 pletely absent from this book. There Is scarcely 

 a reference to the longings of the physicist for an 

 objective aether, save the sentence, " Lorentz had 

 not the heart to abandon the aether which he con- 

 fessedly ' cannot but regard as endowed with a 

 certain degree of substantiality. ' " The readiness 

 to " abandon " well-worn concepts and old- 

 established theory is becoming a marked feature 

 of the thought of physicists to-day. We are wit- 

 nessing at this moment a revolutionary movement 

 in the ' quantum theory ' which at times seems to 

 forget entirely the classical electrical theorj^ and 

 all the wealth of exf)erimental evidence out of 

 which it grew. In the same way the exponents 

 of the principle of relativity have found delight in 

 pouring contempt on the aether as the basis of 

 electromagnetic influence, while in their turn the 

 more conservative of physicists, failing to see how 

 natural was the transition from Lorentz' theory 

 of optical and electromagnetic phenomena in 

 moving bodies to the novel point of view of 

 Einstein, seized upon the somewhat artificial 

 system of clocks by which the latter sought to 

 make his meaning clear, and found in it a 

 laughing-stock. 



It is strange that there has been so much diffi- 

 culty in making the fundamental point of view of 

 this theory clear to those whose interests are ex- 

 perimental rather than theoretical. Many will read 

 Dr. Silberstein 's careful and detailed introduction 

 to it, consider his illustrations, and follow his 

 logic, and yet feel there is something lacking. The 

 ' argument from need ' for an aether is not dealt 

 with. The reluctance that Lorentz had to abandon 

 the aether remains. The seeker after a deeper 

 understanding of the physical is apt to fight shy 

 of a principle which cannot be expressed in terms 

 of concepts to which he can give some * degree of 

 substantiality. ' A systematic exposition of the 

 principle of relativity necessarily consists very 

 largely in the demonstration of invariant proper- 

 ties of certain mathematical relations. Hence it 

 is almost bound to appear a little uninteresting ; 

 NO. 2354, VOL. 94] 



to the experimentalist. Dr. Silberstein com- 

 presses the purely mathematical discussion, 

 and judiciously separates it from the general 

 and descriptive account as far as possible. 

 He shows how many of the invariant re- 

 lations fall simply and naturally into quatern- 

 lonlc form. But little is done to remove 

 the unfortunate impression that relativity Is a fad 

 of the mathematician, and not a thing for the 

 every-day physicist. It is to be feared that many 

 will turn to this book full of hope, and come away 

 from It feeling that the subject is barren for the 

 future. For the universe is not compact of 

 quaternions or matrices. As a physical principle, 

 the principle of relativity needs to be placed in 

 its relation to other great generalisations, such 

 as the conservation of energy and momentum, 

 and the status of the fundamental concepts of 

 space and time in mathematical physics needs to 

 be clearly realised. 



The present book gives an adequate supply of 

 material for meeting these needs; the account of 

 the developments which led up to Einstein's work 

 Is useful and clear; but the reader will need 

 imagination and sympathy if he is to find here an 

 answer to the many difficulties which the subject 

 raises. 



PRACTICAL CHEMISTRY. 

 (i) The Elements of Qualitative Chemical Analy- 

 sis. By Prof. Julius Stieglitz. Vol. I. ; Funda- 

 ' mental Principles and their Application. Pp. 

 ' ■ xi + 312. Vol. ii. : Laboratory Manual. Pp. 

 viii + 153. (London: G. Bell and Sons, Ltd., 

 1914.) Price 65. net each volume. 



(2) Introduction to Modern Inorganic Chemistry. 

 I By Dr. J. W. Mellor. Pp. xvi + 684. (London: 



Longmans, Green and Co., 1914.) Price 45. 6d. 



(3) Allen's Commercial Organic Analysis. \'ol. 

 viii. Fourth edition. Entirely re-written. 

 Edited by W. A. Davis and S. S. Sadtler. 

 Pp. X + 696. (London : J. and A. Churchill, 

 1914.) Price 215. net. 



(4) Handbuch der Arbeitsmethoden in der an- 

 organischen Chemie. Herausgegeben von Dr. 

 Arthur Stabler. Dritter Band. Erste Halfte. 

 Pp. x + 692. (Leipzig: Veit and Co., 1913-) 

 Price 22 marks. 



(5) Quantitative Analysis by Electrolysis. By 

 A. Classen. With the co-operation of H. 

 Cloeren. Translated from the thoroughly re- 

 vised fifth German edition by Prof. W. T. Hall. 

 Pp. xiv + 308. (New York : John Wiley and 

 Sons, Inc.; London: Chapman and Hall, Ltd., 

 1913.) Price los. 6d. net. 



(6) Anleitung ziir Darstellung Phytochemischer 



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