February 28, 1895J 



NATURE 



413 



LETTERS TO THE EDITOR. 



\ The Editor doet not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond -Jiith the writers of, rejected 

 manuscripts intended for this or any other part of NATURE. 

 No notice is taken of anonymous communications. ] 



Liquefaction of Gases. 



In a long letter which you publi!-h»cl in Nature of February 

 14, Mr. Patti>on Muir charged me with .ippropriaiing the work 

 of Olszewski and passing it off as my own. I replied at some 

 length, not on account of the intrinsic importance of the at'ack, 

 but because there are always persons ready to assume ihat a 

 charge of this kind, by whomsoever made, must be unanswer- 

 able unless- it i* ans.vered. But a> I can conceive noihing more 

 unintere ling to yuir readers or mjst-lf, than a mere dialecical 

 controversy with Mr. Muir, my reply to his leiter published on 

 the 2ISI will be biief. 



"A careful smdy" of my previous letter has not enabled Mr. 

 Muir to SI b-ianiia e his original charge of wilful piracy. On 

 the contrary, he entirely shilts his ground. He extracts four 

 clauses from my reply and proceeds to deal with them, ignoring 

 altogeiher the on'y question r>( the smallest imponauce, namely, 

 the one claim made by himself Xo have convicted me of dishonest 

 appropriation of anothe.- man's work. 



The third claim found in my reply by Mr. Muir, which is the 

 all-important one, is, to use hi> own language, that in "1886 I 

 liquefied o.xygen by passing the gas through a long copper coil 

 surrounded fry liquid eihylene, an 1 that my apparatus made it 

 possible to tran>fer the liquid oxygen to a glass vessel wherein 

 it could be used as a cooling agent." Well, the only question 

 here is whether I did or did not do what I claim to have 

 done in a pnfilic leciure dvrlivered and published in the year 

 1886, and ihis quesiion Mr. Muir shirks. 



Until Mr. Paitison Muir can declare that after trial an appa- 

 ratus constructed ace rding to the plan given in 1886 is essenti- 

 ally defective, and will not deliver liquid oxygen in a manner at 

 all comparab e to ihe Olszewski steel cylinder, descrihed in the 

 Cracow Bulletin of 1890, let him acknowledge at least that the 

 case of Prof. 01-zew^kl, which he championed in his last letter, 

 will have to be abandoned. 



Having failed to overthrow a single one of the claims which 

 he himself after "careful study" holds me to have made, Mr. 

 Muir falls back upon a general attack upon the scieniific work 

 "that is attiihuted to the Fullerian Professor at the Royal In- 

 stitution." With what is attrilruied to me by others, I have no 

 concern. The low lemperature work that has been commenced 

 and so far developed in the laboratory of the Royal Insti'ution 

 comprises the following subjects: Construciion of apparatus 

 for the production of liquid air and other gases in quantity, 

 improving high vacuum, vacuum vessels for storage and 

 manipulation of liquid gases, solid air, radiation at low tempera- 

 tures, thermal Iranspartncy of liquid gases, refractive indices of 

 ■oxygen, nitrogen, and air ; spectroscopy of liquid oxygen and 

 air, thermo-electric inversions, latent and specific heats, 

 ■chemical action, magnetic properties, breaking stress of metals, 

 solid matter and argon in liquid air, phosphorescence and 

 photographic action, liquefaction of hydrogen, &c. The 

 abstracts of the results of these investigaiions have been pub- 

 lished, and if Mr. Paitison Muir would only take a little trouble 

 he cjuld find them. In due course, and when I think 

 proper, fuller details will be published. Mr. Muir's case is, 

 however, that my intellectual pap coiies from Cracow, and that 

 I have followe I in the wake of the researches of his client. On 

 referring to Prof. Olszewski's record of woik since his alleged 

 invention of the wa\ to use liquid oxygen as a cooling ai;ent in 

 1890, 1 tin! that with the exception of ihe refractive index of 

 oxygen, which w;is anticipated by Prof Liveing and myself, and 

 an attempt 10 confirm the late Prof. Wroblews i's critical con- 

 stants of hydrogen, the work carried on at the Royal Insiitution 

 and at Cracow have had nothing in common. It is not my 

 business to inquire why Prof. Olszewski should take five years 

 over this work, any more than it is legitimate for Mr. Muir to 

 complan that I ou^hi to have done more with my apparatus of 

 1886, than ciiol a piece of meteorite or expand liquid oxygen 

 into a vacuum. No doubt by imjilication Mr-. Muir intends to 

 convey that any success at the Koyal Institution was due 

 to the use of a steel cylinder instead of the copper 

 ■coil of 1886, and that suggestion I have to emphatic- 



NO. 1322, VOL. 5 l] 



ally contradict, seeing that a steel cylinder never was 

 used in any part of the apparatus employed for 

 the liquefaction of gases. Under the circumstances it will be 

 for Mr. Paitison Muir to explain what new information I could 

 derive from Prof. Olszewski's alleged invention of 1890 which 

 had not been already involved in the construction and use of my 

 1SS6 apparatus. .\ll this, however, does not relieve Mr. 

 Muir from his embarrassment. He charged me with having 

 atiributed to myself work done by other men, and to this 

 charge I pin him. Having failed in his first attack, he has 

 changed his ground, ignored the evidence of dates and facts 

 which he cannot overthrow, and made a second attack in a form 

 chosen by himself. This also has failed ignominiously. It is 

 to be hoped that in future, when scientific investigators enter on 

 priority discussions, ihe real combatants will be left to their 

 polemics without the interference of third persons. 



Royal Institution, February 26. James Dewar. 



On Certain Questions of the Theory of Gases. 



§1.1 PROPOSE to answer two questions : — 



(1) Is the Theory of Gases a true physical theory as valuable 

 as any other physical theory? 



(2) What can we demand from any physical theory ? 



The first question I answer in the afiirmative, but the second 

 belongs not so much to ordinary physics (let us call it ortho- 

 physics) as to what we call in Germany metaphysics. For a 

 long time the celebrated theory of Boscovich was the ideal of 

 physicists. According to his theory, bodies as well as the ether 

 are aggregates of material points, acting together with forces, 

 which are simple functions of their distances. If Ihis theory 

 were to hold good for all phenomena, we should be still a long 

 way off what Fausl's/a'««/Hj- hoped to attain, viz. to know 

 everything. But the difficulty of enumerating all the material 

 points of the universe, and of determining the law of mutual 

 force for each pair, would be only a quantitative one ; nature 

 would be a difticult problem, but not a mystery for the human 

 mind. 



When Lord Salisbury says that nature is a mystery,' he means, 

 it seems to me, that this simple conception of Boscovich is 

 refuted almost in every branch of science, the Theory of Gases 

 not excepted. The assumption that the gas-molecules are 

 aggregates of material points, in the sense of Boscovich, does 

 not agree with the facts. But what else are they ? And what 

 is the ether through which they move? Let us again hear 

 Lord Salisbury. He says : 



"What the atom of each element is, whether it is a move- 

 ment, or a thing, or a vortex, or a point having inertia, all 

 these questions are surrounded by profound darkness. I dare 

 not use any less pedantic word than entity to designate the 

 ether, for it would be a great exaggeration of our knowledge if 

 I were to speak of it as a body, or even as a subs'ance " 



If this be so— and hardly any physicist will contradict this — 

 Ihen neither the Theory of Gases nor any other physical theory 

 can be quite a congruent account of facts, and I cannot hope with 

 Mr. Burbury, that Mr. Bryan will be able to deduce all the 

 phenomena of spectroscopy from the electromagnetic theory of 

 light. Certainly, therefore, Hertz is right when he says:'- 

 " The rigour of science requires, that we distinguish well the un- 

 draped figure of nature itself Irom the gay-cohiured vesture with 

 which we clothe it at our pleasure.'' But I think the predilection 

 for nudity would be carried too far if we were to forego every 

 hypothesis. Only we must not demand too much from 

 hypotheses. 



It is curious to see that in Germany, where till lately the 

 theory of action at a distance was much more cultivated than 

 in Newton's native land itself, where Maxwell's theory of 

 electricity was not accepted, because it does not start from quite 

 a precise hypothesis, at present every special theory is old- 

 f.-.shioned, while in Er gland interest in the Theory of Gases is 

 still active ; zide, among others, the excellent papers of Mr. 

 Tail, of whose ingenious results I cannot speak too highly, 

 though I have been forced to oppose them in certain points. 



Every hypothesis must derive indubitable results from 

 mechanically well-defined assumptions by mathematically cor- 

 rect methods. If the results agree with a large series of facts, 

 we must be content, even if the true nature of facts is not 



1 Presidenlial Address lo the British Associalion at Oxford. 

 - Hertz, " Untersuchungen fiber die Ausbreilung dcr cicktrischcn Kraft, 

 p. 3r. ^Barth, Leipzig, 1S92.) 



