NA TURE 



\75 



THURSDAY, SEPTEMBER 21, i 9 n 



THE PROGRESS OF PHYSICS. 

 The Progress of Physics during Thirty-three Years 

 (1875-1908). Four lectures delivered to the Univer- 

 sity of Calcutta during March, 1908. By Arthur 

 Schuster, F.R.S. Pp. x+ 164. (Cambridge: Uni- 

 versity Press, 191 1.) Price 35. 6d. net. 

 IN the year 1908 Prof. Schuster during his visit to 

 India gave to the University of Calcutta four 

 lectures, which he has now incorporated into a book, 

 dealing with the progress which had been made in 

 his subject during his own active lifetime, namely 

 from the year 1875 onward. 

 The scope of the book he thus explains : — 



" It is my aim to trace the changes in our point of 

 view, rather than to give an historical account of the 

 sequence of the discoveries which make this period 

 memorable. ... I prefer to be frankly subjective, and 

 warn you beforehand that my account will be frag- 

 mentary, and to a great extent reminiscent of those 

 aspects which have come under my own personal 

 view." 



In his preliminary survey of the state of the science 

 before 1875 he contrasts the endeavour at that time 

 prevalent to get a clear idea of the mechanism under- 

 lying the various processes, with the "blinkers" which 

 are in some quarters willingly accepted now, not only 

 as inevitable but as praiseworthy instruments con- 

 ducive to a rational philosophy. The one idea of 

 Energy is now sometimes upheld as dominating the 

 field, and rendering unnecessary all more picturesque 

 inquiry into forces and motions and coordinates in 

 detail. 



It is true that ignorance of detail may often be a 

 dominant feature in both methods of dealing with 

 phenomena ; but the modern treatment, as he says — 

 "glorifies our ignorance, while the other accepted it 

 as a regrettable necessity." . . . The "vagueness 

 which used to be recognised as our great enemy is 

 now being enshrined as an idol to be worshipped." 



At the beginning of the period dealt with by the 

 author this tendency hardly existed : — 



"The tendency to hide ignorance under the cover 

 of a mathematical formula had already appeared, but 

 was not openly advocted ; hence students were still 

 taught to form definite ideas of the processes of 

 nature." 



So far an advantage seems to him to lie with the 

 past; but then, on the other hand, he recollects a less 

 excellent tendency which then existed to regard the 

 scope of physics as already fairly complete, with all 

 the main avenues explored, and only side tracks and 

 subsidiary paths awaiting the would-be discoverer — 

 whose aim sometimes was to get hold of some neg- 

 lected residual effect, by employing extremely sensi- 

 tive instruments and applying power enough to bring 

 it within the compass of observation ; and whose other 

 and highly estimable aim was to measure with careful 

 accuracy effects already known. 



This condition of things Prof. Schuster thus 

 describes : — 



NO. 2l86, VOL. 87] 



"In many cases the student was led to believe 

 that the main facts of nature were all known, that 

 the chances of any great discovery being made by 

 experiment were vanishingly small, and that there- 

 fore the experimentalist's work consisted in deciding 

 between rival theories, or in finding some small 

 residual effect which might add a more or less im- 

 portant detail to the theory." 



It is perhaps singular that such an outlook should 

 have so closely preceded an outburst of novelties such 

 as have of late years aroused the enthusiasm of the 

 worker, as well as the occasional derision of the 

 sceptical critic. 



" Looking back now on this period, when RSntgen 

 rays and radio-activity were undreamt of, we may 

 well learn to be cautious in our own predictions of 

 the future." 



Nevertheless, some of the discoveries were made 

 in what may be called the old-fashioned way, one 

 example being of the first magnitude : — 



"A typical example of a great discovery brought 

 about by the method indicated by Maxwell is 

 furnished by Rayleigh's measurements which cul- 

 minated in the discovery of argon, through a research 

 undertaken to determine with accuracy the density 

 of gases. ... It is nevertheless indisputable that 

 the greatest discoveries, both formerly and in recent 

 years, have not originated in the hunt of residuals." 



No ; they have sometimes been begun accidentally, 

 but they have been followed up by those who have 

 been guided by a clue of theory; and some of the 

 most splendid have been made by mathematical phy- 

 sicists who were clearly conscious all the time of what 

 their aim was and what was the meaning of the 

 phenomena they observed. 



"Altogether I am doubtful," says Prof. Schuster, 

 " whether any great discovery has ever been made by 

 anyone who has only aimed at recording a number 

 of facts." 



Those who contemn theory, and who affect to dis^ 

 believe the explanation which physicists give of re- 

 cently observed phenomena, would do well perhaps 

 to realise that ultra-scepticism has often been a drag 

 on scientific progress, as well as occasionally a safe- 

 guard and a help. 



As an example tending in this cautionary direction 

 we may quote from the author as follows : — 



" The frame of mind with which the academic phy- 

 sicist [or, we might add, the academic chemist] looked 

 upon investigations of the passage of electricity 

 through gases, might be made the subject of instruc- 

 tive comment. The facts, so far as they had been 

 ascertained, did not fit in with recognised views : 

 hence they were ignored, and students were warned 

 off the subject. There was a feeling that perhaps in 

 a century or so the question might be attacked, but 

 that in the meantime it had better be left to be played 

 with by cranks and visionaries. No criticism was 

 more frequent, at that time, than that of charac- 

 terising as premature any new idea or fresh line of 

 investigation in this direction ; as if any advance of 

 science has ever been made which was not premature 

 a fortnight before it was made." 



The extreme usefulness of a working hypothesis or 

 theoretical clue can scarcely be emphasised better than 

 by the following : — 



M 



