7o6 



NA TURE 



[June 3, 1922 



the sources to which an author attaches most weight, 

 and here Mr. Hetherington proves himself at once 

 cathohc and discriminating. The older European 

 authorities like Dr. Bushell, Sir A. WoUaston Franks, 

 and his successors in the famous school of the British 

 Museum have naturally been used to great advantage, 

 while the writings of Mr. Berthold Laufer and other 

 special workers in the history of early Chinese art have 

 been drawn upon with discrimination. One. would say 

 off-hand that no modern opinion of value has been 

 overlooked, while each, in turn, is supported or 

 refuted from authoritative sources. This piece of 

 patient toil has been carried out with much discrimina- 

 tion, as is especially manifest in the author's appraise- 

 ment of the information that is to be obtained only 

 from Chinese sources. The valuable original sources 

 are set out in a select bibliography, where a list of the 

 most important English and French works on the 

 subject is also given. 



The illustrations of the ancient wares, gathered from 

 many sources, are worthy of the book and really illus- 

 trate it, while they have been chosen in a truly 

 commendable way. Mr. Hetherington explains the 

 manner of his choice in a few words which deserve to 

 be quoted : "In selecting the illustrations I have 

 followed a somewhat unusual course. The specimens 

 chosen are not the rarest and most costly examples, 

 nor are they taken from the great National Museums. 

 I have illustrated typical pieces of good quality in 

 the possession of private collectors. The ordinary 

 person, in my opinion, wants to see the kind of thing 

 he may hope to acquire for himself ; not specimens 

 worth a king's ransom which are never likely to adorn 

 his cabinet." 



William Burton. 



Optical Theories. 



(i) Die Prinzipien der physikalischen Optik. His tori sch 

 und erkenntnispsychologisch entwickelt. Von Ernst 

 Mach. Pp. x + 444. (Leipzig: J. A. Barth, 1921.) 

 48 marks. 



(2) Optical Theories : Based on Lectures delivered before 

 the Calcutta University. By Prof. D. N. Mallik. 

 Second edition, revised. Pp. vii + 202. (Cambridge : 

 At the University Press, 1921.) 165. net. 



(i) TT" RNST MACH died in February 1917, at a time 

 I > when civiHsed humanity was too busy to 

 notice the passing of one who had made his influence 

 felt wherever interest existed for the understanding 

 of the fundamentals of mechanical and physical 

 knowledge. The present work was published in 1921, 

 but it is not a posthumous work, for it was ready before 

 the war, and in fact the preface is dated July 1913. 

 NO. 2744, VOL. 109] 



Although it went to press in 19 16, the War and other 

 causes delayed its issue. 



As the title indicates, the book is an historical and 

 epistemological account of the development of the 

 principles of physical optics, the writer's aim being 

 similar to that in his famous book on Mechanics. The 

 book is thus not really a history, but rather a statement 

 of the progress of ideas and of the manner in which 

 they arose in the minds of their originators. Nobody 

 who has read other books by Mach will need to be told 

 that this volume is interesting and instructive : the 

 description of the way in which the fundamental 

 notions such as periodicity and asymmetry of the light 

 ray emerged, is as fascinating as any romance. 



The present volume was intended as a first part of 

 a larger work : subjects like theories of the ether and 

 relativity were reserved for the second volume. But 

 the author's foreboding that this second volume would 

 not be written by himself was unhappily justified. 



Many points of interest emerge in the course of this 

 history. Full tribute is paid to Newton's genius — it 

 was Newton who first realised clearly the periodic 

 nature of the light ray, later worked up into the wave 

 theory, and its asymmetry, which became the theory of 

 polarisation and the notion of the transverse light- 

 vector. When Fresnel first reached the conclusion 

 that light oscillations are transverse, the revolution in 

 ideas was too great for even Arago, who refused to be 

 associated with Fresnel's idea, and in fact, although 

 Fresnel and Arago collaborated in many pieces of 

 work, the transverse vibration theory was put forward 

 in a paper bearing only Fresnel's name. Young's 

 experiments did not at once receive the recognition 

 they deserved, owing to the mistaken and reactionary 

 servitude to all that was supposed to have emanated 

 from Newton. The author has not much good to say 

 about Schopenhauer's attempt at a theory of colours, 

 while faint praise is all that is allotted to Goethe. 



As already remarked, relativity as such is not dis- 

 cussed in this book, and even when -Michelson's inter- 

 ferometer is described nothing is said about the 1887 

 experiment. Nevertheless the author felt it incumbent 

 upon him to decline the honour of having been the 

 herald (Wegbereiter) of relativity. On various grounds 

 he refuses to accept the theory — presumably this 

 refers to the restricted theory — and, while acknow- 

 ledging the value of the relativist researches, he doubts 

 whether the theory itself will find a lasting place in the 

 physical Weltbild of the future. Mach asks : " Will 

 the theory of relativity be more than an ingenious 

 aperfu in the history of this science ? " Would Mach's 

 opinion have been affected by the events of 191 9 ? 



(2) The lectures delivered by Prof. Mallik at Calcutta 

 in 191 2 were published in book form in 19 17, and the 



