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NATURE 



[September 21, 191 1 



"If we look back upon these experiments now, they 

 may be used to point the moral that experiments con- 

 ducted in what is sometimes considered to be the true 

 philosophic spirit, where the investigator without any 

 preconceived theories or notions simply wishes to 

 classify facts, seldom lead to any valuable results. 



" Progress began when the subject was attacked 

 with some definite object in view, either some theory 

 however crude which had to be supported, or some 

 numerical connection which had to be investigated." 



It has been one of the features of Sir J. J. Thom- 

 son's work, for instance, that theory and experiment 

 have gone hand in hand and have been published to- 

 gether. The reviewer has heard this feature objected 

 to, but it is more than justified. The publication of 

 the great discovery which is being here specially re- 

 ferred to is thus mentioned by Prof. Schuster : — 



"The lecture in which the above experiments were 

 described, was delivered to the British Association fat 

 Dover] on the occasion of the visit of members of the 

 French Association, which met concurrently at Bou- 

 logne. 1 It at once carried conviction, and, though to 

 those who had followed the gradual development of the 

 subject it only rendered more certain what previous 

 experiments had already plainly indicated, the scien- 

 tific world seemed suddenly to awake to the fact that 

 their fundamental conceptions had been revolutionised. 

 A new era of science begins at this point." 



Prof. Schuster had himself made experiments which 

 would have received their quantitative explanation 

 had the idea of a separate atom of electricity detached 

 from matter been at that time fairly conceivable. 

 But, as he says — in full accordance with the attitude 

 of most others at the time — 



"The separate existence of a detached atom of 

 electricity never occurred to me as possible, and if it 

 had, and I had openly expressed such heterodox 

 opinions, I should hardly have been considered a 

 serious physicist, for the limits to allowable heterodoxy 

 in science are soon reached." 



There were not wanting critics to emphasise the 

 heterodoxy of the idea, even when the discovery had 

 been made; and chemical scepticism concerning ions 

 exerted a retarding effect in Britain : — 



"This ionic theory of gas discharges, while ignored 

 in England, made good progress abroad; Arrhenius 

 adopted it, as well as Elster and Geitel." 



But it is in connection with the subject of terrestrial 

 magnetism and its explanation that the author makes 

 the most biting comment : — 



"There can only be one solution of the problem, 

 and if we can explain any magnetic effect on the 

 earth's surface by outside forces, it follows that it 

 cannot at the same time be explained by internal 

 forces. This remark disposes of a good deal of the 

 criticism lavished on pioneer attempts to open out 

 this region of science. Though this criticism is often 

 confined to a judicious shrugging of the shoulders, 

 it stops scientific progress more effectually than active 

 opposition, and is apt to become a constitutional habit 

 with those who give way to its undoubted tempta- 

 tions." 



Of course, caution is necessary; but on the whole, 

 says the author — 



' The title originally was " On the Existem e of M than the 



Atoms, but was changed when the papei the Phihsofihu al 



me, xlviii., p. 565(1809), to"On tl,. I: 1 , 



NO. 2 1 86, VOL. 87] 



"The state of plasticity and flux — a healthy state, 

 in my opinion — in which scientific thought of the 

 present age adapts itself to almost any novelty, is 

 illustrated by the complacency with which the most 

 cherished tenets of our fathers are being abandoned." 



For instance, 



" Nowadays the student finds little to disturb him, 

 perhaps too little, in the idea that mass changes with 

 velocity ; and he does not always realise the full mean- 

 ing of the consequences which are involved." 



This part of the treatise is so important, and the 

 usefulness of theory as a guide to discovery is so 

 vital, that we must dwell on the author's treatment 

 of the more philosophical aspect of physics with 

 special interest. 



First of all he admits that we must allow something 

 for intuition : — 



" When we consider two rival theories in any branch 

 of human knowledge, we are sometimes drawn to- 

 wards one or towards the other, not by any process 

 of reasoning, but by an instinctive feeling which may 

 be so strong that we unhesitatingly reject one of the 

 alternatives. . . . The strongest of our scientific 

 ' instincts ' is our ultimate belief in the simplicity of 

 nature. If both light and electrical attractions are 

 transmitted through a medium, it would revolt our 

 feelings — that is to say, our non-reasoning faculties 

 — to assume, without strong evidence to the contrary, 

 that two different media exist for the two manifesta- 

 tions." 



But it is not to be supposed that the intuition is 

 always right. The example which the author takes 

 — in order to illustrate the useful consequences of even 

 an erroneous theory — is not one with which the re- 

 viewer sympathises, for he is one of those who desire 

 dogmatically to deny the possibility of physical action 

 except through a medium ; whereas Prof. Schuster 

 says :• — 



"To me it seems that the dogmatical denial ol 

 action at a distance is a survival of the ancient 

 anthropomorphic explanation of natural phenomena." 



He admits, however, with cordiality that the search 

 for the medium has resulted in many discoveries, and, 

 like many other theoretical clues — whether correct or 

 not — has been justified by results. From this, he 

 says : — 



"Two lessons may here be learned. One is, that 

 the temporary success of a doctrine does not neces- 

 saiily justify the grounds of its foundation; and the 

 other, that progress in science is more often achieved 

 by a definite hypothesis, which may be followed up 

 and tested, than by a wider and perhaps more philo- 

 sophic doctrine, which cannot be disproved because 

 it does not endeavour to go deeper than the mere 

 descriptive classification of phenomena." 



In the same spirit as that in which he maintains the 

 possibility or conceivability of physical action at a 

 distance, the author is not frightened away from any 

 hypothesis because of its excessive strain upon ordinary 

 common sense. For instance, he is able to contem- 

 plate the view that an atom or an electron may be a 

 source or a sink of fluid, continually appearing out of 

 ' nothing at some points and continually going out of 

 existence at others. 



"The universe must have begun by a process which 

 lies outside physical laws, and it seems to me no 



