544 



NATURE 



[April 29, 1922 



have accrued in the operation of these factories will 

 form a permanent record of the application of scientific 

 method to problems of chemical industry, as well as 

 affording typical examples for the use of students as 

 well as of manufacturers. It is to be regretted that 

 Queen's Ferry factory, which embodies so much 

 original work in plant construction, is now for dis- 

 posal, but it is understood that while there is yet 

 time the Disposals Board have acquiesced in an 

 arrangement for students to study the plant. A 

 course of this kind with Mr. Macnab's volumes as 

 text-books should prove a very valuable means of 

 instruction. 



Popular Expositions of Relativity. 



Relativity and the Universe: A Popular Introduction 



into Einstein's Theory of Space and Time. By Dr. 



Harry Schmidt. Authorised Translation by Dr. 



Karl Wichmann. Pp. xiii + 136. (London: Methuen 



and Co., Ltd., 1921.) 55. net. 

 The Ideas of Einstein's Theory : A Theory of Relativity 



in Simple Language. By Prof. J. H. Thirring. 



Translated by R. A. B. Russell. Pp. xv 4-167. 



(London : Methuen and Co., Ltd., 1921.) 55. net. 

 An Introduction to the Theory of Relativity. By L. 



Bolton. Pp. xi + 177. (London : Methuen and Co., 



Ltd., 1921.) 55. net. 

 Relativity and Gravitation. Edited by J. Malcolm Bird. 



Pp. xiv + 245. (London: Methuen and Co., Ltd., 



1921.) 85. 6d. net. 

 The Rudiments of Relativity : Lectures delivered under 



the Auspices of the University College, Johannesburg, 



Scientific Society. By Prof. J. P. Dalton. Pp. vi + 



105. (London : Wheldon and Wesley, Ltd., 1921.) 



55. net. 

 Die Einsteinsche Gravitationstheorie : Versuch einer 



allgemein verstandlichen Darstellung der Theorie. Von 



Prof. G. Mie. Pp. iv + 67. (Leipzig: S. Hirzel, 



1921.) 7 mk. 



HERE are six accounts of the Relativity theory 

 designed for the general reader. The first 

 four hail from Messrs. Methuen, who had the enterprise 

 to secure an English translation of Einstein's own 

 popular exposition, and have also recently published 

 a translation of Weyl's " Space, Time and Matter." 

 The fifth is published in Johannesburg by the Council 

 of Education, Witwatersrand. The last comes from 

 the pen of an eminent German professor of physics. 



In surveying such a collection it is appropriate to 

 quote from the last named. " We cannot penetrate 

 into the thought-world of a symphony by reading a 

 NO. 2739, VOL. 109] 



description of it, be it by the most distinguished 

 musical critic. The symphony must be heard. The 

 more we analyse it note by note, and the more deeply 

 we understand the relations of the notes, the more do 

 we come into the real meaning of the work." 



That is the feeling which emerges after going one after 

 another through many attempts to describe this new 

 theory without asking the reader that he should first 

 equip himself for the act of appreciation by an intimate 

 study of the technique and terminology of geometry, of 

 the significance of Newton's theory of gravitation and 

 his system of mechanics both as an explanation of 

 known phenomena and as forming the whole basis of 

 the further development of physical science. But even 

 granting these prime requisites, the reader is desired, 

 on the strength of the reading of a few simple pages, to 

 readjust the whole of his outlook on the world to an 

 degree even greater than that required for one brought 

 up in a classical school of art to comprehend the 

 strivings of the moderns to find a new mode of expres- 

 sion for the thoughts of a new age. 



This much is certain, that there is no short-cut to an 

 understanding of Einstein's achievement. What is the 

 most that we can expect from these many attempts to 

 supply the public with some answer to their inquiries 

 for light on this latest achievement of the imagination 

 and intellect in co-operation ? We may legitimately 

 ask for some presentation of the historical setting. 

 But even here we are faced with a great difficulty in 

 providing an account which is free on the one hand 

 from technical difficulties and on the other from mis- 

 leading vagueness. For the precise statement of the 

 actual achievements of Newton is in itself a matter 

 requiring so much detail that the majority of our 

 university students would not show up well in an 

 examination on this subject. They are content with 

 a parrot-like learning of the conventional language in 

 which the laws of motion are expressed, and a false 

 facility in doing problems without any reference to 

 their physical significance. Meanwhile the Newtonian 

 conceptions of space and time are absorbed as if they 

 were strictly obvious, whereas the mere fact of the 

 existence of Newton's definitions of absolute space and 

 time shows that after all his investigations he found 

 himself bound to postulate something which his reason 

 and conscience could not justify. Newton's absolute 

 space, like Euclid's axiom of parallels, were last con- 

 fessions of remaining mysteries rather than preliminary 

 statements of the obvious. 



Yet it is not possible to appreciate the bearing of the 

 relativity theory without appreciating first the point 

 at which the classical mechanics is unsatisfactoryg 

 For it is perhaps the greatest merit of Einstein's work 

 that it gives us something which is more satisfactory 



