Oct. 25, 1877] 



NA TURE 



545 



which seemed so unmistakably demonstrated, though transcend- 

 ing all previous experience. But after some little time the 

 question was raised, whether the effect was not really due to an 

 intermediate action of that mode of Radiant Force which we call 

 Ittat, upon the attenuated vapour of which it was impossible 

 entirely to get rid ; and the result of a most careful and elaborate 

 experimental inquiry, in which nature has been put to the ques- 

 tion in every conceivable mode, has been to make it (I believe) 

 ahnost if not quite certain, that the first view was incorrect, and 

 that Heat is the real moving power, acting under peculiar con- 

 ditions, but in no new mode." — Lectures on Alesnurisin and 

 SpiritttaJism^ p. S. 



" I hold the warning given by the history of this inquiry, in 

 regard to the duty of the scientific man to exhaust every possible 

 mode of accounting for new and strange phenomena, before 

 attributing it to any previously unknown agency, to be one of 

 the most valuable lessons afforded by Mr. Crookes's discoveries. 



" Now I maintain that it requires exactly the same kind of 

 specially trained ability to elicit the truth in regard to the 

 phenomena we are now considering, as has been exerted in the 

 researches made by the instrumentality of the Spectroscope and 

 the Radiometer. And I cannot but believe that if Mr, Crookes 

 had been prepared by a special training in the bodily and mental 

 constitution, abnormal as well as normal, of the Human instru- 

 ments of the Spiritualistic inquiries, and had devoted to them the 

 ability, skill, perseverance, and freedom from prepossession, 

 which he has shown in his Physical investigations, he would have 

 arrived at conclusions more akin to those of the great body of 

 scientific men whom I believe to share my own convictions on 

 this subject." — Op. cit., p. 70. 



No one, I think, can fj.il to see that in speaking of Mr. 

 Crookes's "most admirable invention," and in giving him the 

 fullest credit for the "ability, skill, perseverance, and freedom 

 from prepossession," with which he had carried on his investiga- 

 tions in regard to it, I eulogised him as warmly as if I had 

 never come into collision with him. It must also be apparent 

 to any reader of these lectures, that I did not impute to him any 

 blame for having originally fallen into an error shared at the 

 time by the " eminent Physicists in whose judgment the greatest 

 confidence was placed ;" and that my reason for bringing forwards 

 the subject was to enforce the lesson, that " no new principle of 

 action has any claim to scientific acceptance, save after an ex- 

 haustive inquiry as to the extent to which the phenomena can be 

 accounted for, either certainly or probably, by agencies already 

 known." 



Circumstances to which I shall presently advert having made 

 me feel it desirable that this " lesson " should be yet more fully 

 and emphatically set forth, I applied myself to a careful reperusal 

 of Mr. Crookes's papers in the Proceedings of the Royal Society, 

 with the most earnest desire to present a true history of the whole 

 inquiry ; and I availed myself of the opportunity kindly afforded 

 ma by the editor of the Nineteenth Century, to place before the 

 public what I believed to be a fair statement of the case, with 

 the lessons it conveyed. 



Commencing with a description of the phenomena presented 

 by the Radiometer when it was first exhibited by Mr. Crookes at 

 the soiree of the Royal Society, I thus continued : — 



"It is scarcely surprising, then, that a general impression 

 should at once have prevailed that a capital discovery had been 

 made — that of the direct mechanical action cf light ; which, though 

 not indicating the existence of a new force in nature, showed 

 that the most universally diffused of all forces, next to gravita- 

 tion, has a mode of action which was previously not merely 

 unknown, but altogether unsuspected. And this impression was 

 not confined to those who had only a general acquaintance with 

 Physical Optics ; for it was shared by the greatest masters of that 

 department of science, who had followed the course of the expe- 

 rimental researches on which Mr. Crookes had been for some 

 time engaged, and of which this discovery was the culmination." 

 —Niruteenih Century, April, 1877, p. 243. 



I then went on to give, from Mr. Crookes's papers, a history 

 of the investigations which had led him up to the Radiometer; 

 and showed (p. 249) that at that stage of the inquiry, the argu- 

 ment for the directness cf radiant repulsion, deducible from what 

 was then supposed to be a fact — the increase of the rapidity of 

 the rotation in proportion to the perfection of the vacuum — 

 "seemed alike valid and cogent." 



I next sketched the history of the opposite view originally 

 propounded by Prof. Osborne Reynolds, supported by Dr. 

 Schuster's experiment, and finally established by Mr. Crookes's 

 own later researches, which have culminated in the doctrine of 



' ' heat reaction "now generally accepted. In reference to Mr. 



Crookes's own part in these subsequent inquiries, I say later on 

 (p. 254), that "no sooner was adequate ground shown for calling 

 in question his interpretation of the phenomena, and a vera causa 

 found in an agency already known, than Mr. Crookes evinced 

 the spirit of the true philosopher in varying his experiments in 

 every conceivable mode, so as to test the validity of his original 

 interpretation." And again in the next page I speak ot his 

 "carrying out this beautiful inquiry in a manner and spirit 

 worthy of all admiration." — What higher praise could be given 

 to a scientific investigator ? 



Having brought the history to its conclusion, I thus proceed : — 



" Before adverting to the lessons which this remarkable history 

 seems to me to convey, I would point out that this change of 

 interpretation of the facts discovered by Mr. Crookes, does not 

 in the least diminish either the interest of the facts themselves 

 or the merit of his discovery. Nor is the value of his Radiometer 

 in any degree lowered by the demonstration that it does not (as 

 Mr. Crookes at first supposed) afford an absolute mechanical 

 measure of radiant energy under any of its aspects. What 

 (according to present views) it really does measure, is the amount 

 of ' heat reaction ' producible in gaseous atmospheres of 

 different kinds and of different degrees of attenuation. And 

 such a precise method of measurement appears more likely than 

 any other mode of investigation, to furnish a test of that kinetic 

 theory of gases, the recent development of which by Prof. Clerk- 

 Maxwell is regarded by competent judges as constituting (if it 

 should receive such verification) the most important advance ever 

 made in molecular physics. Most deservedly, therefore, did Mr. 

 Crookes receive from the Royal Society the award of one of its 

 chief distinctions." {Loc. cit., p. 251.) 



To this I may add that I personally congratulated Mr. Crookes 

 most cordially on that occasion, and expressed to him the deep 

 interest with which I had followed his researches throughout. 

 And though I had next to show that Mr. Crookes has another side 

 to his mind, which makes Mr. Crookes the "spiritualist " almost 

 a different person from Mr. Crookes the " physicist," I carefully 

 guarded what I had to say on this point in the following words : — 

 " I would not be thought for one moment to disparage Mr. 

 Crookes's merits as the inventor of the Radiometer, by now bring- 

 ing into contrast with the admirable series of scientific investiga- 

 tions which led up to that invention, what I cannot but regard 

 as his thoroughly unscientific course in relation to another doc- 

 trine of which he has put himself prominently forward as the 

 champion." 



I cannot but surmise that Prof. Carey Foster'must have read 

 my paper rather carelessly, and have applied to Mr. Crookes, 

 the inventor of the Radiometer, the depreciatory remarks I felt 

 called upon to make in regard to Mr. Crookes, the supporter of 

 a system, a large proportion of which even Mr. D. D. Home has 

 recently denounced as " a seething mass of folly and impos- 

 ture.'" If Prof. Carey Foster knew as much as I do of the 

 mischief which this Mr. Crookes has done, especially in the 

 United States, on the one hand to his own reputation and to 

 that of British science,- and on the other to public morality, by 

 the facility with which he has lent himself to the support of 

 frauds as wicked as those by which fortune-tellers delude igno- 

 rant and credulous servant-girls, he would not wonder that I 

 should feel called upon to show that the high scientific ability of 

 Mr. Crookes, the Physicist, neither prevents him from believing 

 in his own day-dreams, nor renders him a match for the cunning 

 of the clever female cheats who play upon his Spiritualistic 

 " prepossessions." 



1 now pass to the second part of my defence ; and shall show 

 that for " making it appear that Mr. Crookes had put a wrong 

 interpretation upon his own results," I can adduce adequate 

 justification from his own published statements. 



Of the "repulsion accompanying radiation" shown in his 

 early experiments by the swinging-round of the pith bar, Mr. 

 Crookes said, in 1S74 [Phil. Mag., vol. xlviii., p. 94), "My 

 mon impression is that it is directly due to the impact of the -ivaves 



* See his " Lights and Shadows of Spiritualism," containing an unsparing 

 exposure of its " delusions," its " absurdities," and its " trickeries. " 



2 On the strength of a private letter from Mr. Crookes, which has beeil 

 published (m/ae siiiiiic) in the American newspapers, a certain Mrs. or Miss 

 Eva Fay announced her "spiritualistic" performances as "endorsed by 

 Prof. Crookes and other Fellows of the Royal Society." The particulars of 

 the complete public exposure of this woman's disgraceful frauds, showing 

 that Mr. Crookes's seicniijic tests are no more worthy of trust than the late 

 Prof Hare's experimental demonstration of the immortality of the sold, 

 will appear in the forthcoming number of Ffosti/s Magazine, 



