June 30, 1898] 



NATURE 



199 



LETTERS ^ TO THE EDITOR 

 \_The Editor does not hold himself responsible for opinions ex 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of NATURE. 

 No notice is taken of anonyviotts cotnmtinications.'\ 



Liquid Air at One Operation. 



It is to be hoped that personal matters will not divert at- 

 tention from the very interesting scientific questions involved. 

 The liquefaction of air at one operation by Linde and Hampson 

 is indeed a great feat and a triumph for the principle of re- 

 generation. But it must not be overlooked that to allow the 

 air to expand without doing work, or rather to allow the work 

 of expansion to appear as heat at the very place where the 

 utmost cooling is desired, is very bad thermodynamics. The 

 work of expansion should not be dissipated within, but be con- 

 ducted to the exterior. 



I understand that attempts to expand the air under a piston 

 in a cylinder have led to practical difficulties connected with the 

 low temperature. But surely a turbine of some sort might be 

 made to work. This would occupy little space, and even if of 

 low efficiency, would still allow a considerable fraction of the 

 work of expansion to be conveyed away. The worst turbine 

 would be better than none, and would probably allow the pres- 

 sures to be reduced. It should be understood that the object 

 is not so much to save the work, as to obviate the very prejudicial 

 heating arising from its dissipation in the coldest part of the 

 apparatus. It seems to me that the future may bring great 

 developments in this direction, and that it may thus be possible 

 to liquefy even hydrogen at one operation. Rayleigh. 



Terling Place, Witham, June 26. 



Liquid Hydrogen. 



I OBSERVE with some amusement that you still allow Mr. 

 Hampson to embellish your columns with vain repetitions of 

 accusations which he was compelled to withdraw when he met 

 me face to face at the meeting of the Society of Chemical 

 Industry, 



It is idle to discuss any question with a man whose notion of 

 argument is to restate in somewhat different language what has 

 already been refuted, and then to assert that the accuracy of his 

 propositions has not been questioned. 



Mr. Hampson must be a singularly dull person if he fails to 

 appreciate the magnitude of the draft he makes upon the 

 credulity of the world. He asks men of the world to believe 

 that he, being convinced of the general dishonesty of Royal 

 Institution methods, and being in possession of a novel and 

 valuable invention, fully completed but not protected by patent, 

 came unbidden and unsought to reveal all the details to a man 

 whom he knew to be my assistant. 



He further expects the world to believe that having thus given 

 himself away, he refrained from protecting his invention until 

 the rival inventor had had ample time to profit by his childlike 

 simplicity. But even this is not all ; for the world is further 

 asked to believe that after he had placed the Royal Institution 

 in possession of full information concerning a finished invention, 

 it took me more than a year to utilise his generosity, while in 

 the interval Dr. Linde had published his method and apparatus. 

 Does not all this amount to rather a large order ? 



But perhaps no one can answer Mr. Hampson so well as Mr. 

 Hampson himself. At the meeting of the Society of Chemical 

 Industry on May 2, Mr. Hampson expressed himself as follows 

 [The fournal of the Society of Chemical Industry, No. 5, vol. 

 vvii. p. 421) : — " Prof. Dewar will do me the justice to say that 

 I have nowhere published any statement that he had made use 

 of anything I had communicated, or of what I had invented. I 

 have, therefore, nothing to withdraw, since I have nowhere sug- 

 gested that a communication had been passed on to him, . . . 

 I am not to be understood as saying that my proposal was passed 

 on to Prof. Dewar." 



What is Mr. Hampson to be understood as saying in the 

 letters you have published, if not the precise contrary of what 

 he said when brought to book at the Society of Chemical 

 Industry? 



How otherwise is the "credit of science" involved? 



It is worth noting that in Match 1896, a year and a half after 

 the fiimous interview with Mr. Lennox, Mr. Hampson threatened 

 Messrs. Lennox, Reynolds, and Fyfe with legal proceedings on 

 the ground that a lecture apparatus made for my Chemical 



NO. 149b, VOL. 58] 



Society paper of 1895, and subsequently advertised by them in 

 Nature, was an infringement of his patent. They replied that 

 he might take any action he pleased. He has never taken any, 



Mr. Hampson's extract from my speech at the Society of 

 Arts, reported in the Journal for March 11, 1898, is so com- 

 pletely isolated from the context as to convey a totally wrong 

 impression. When Mr. Hampson made it, he had before him 

 my statement that "although this regeneration system had 

 been carried by Dr. Linde to the acme of perfection, no one 

 who constructed low temperature apparatus rejected the cool gas 

 without utilising it ; the great advance was that Dr. Linde did 

 so completely.' 



If all that Mr. Hampson wants is "recognition in historical 

 or explanatory works " of his claim to be the inventor of a 

 general claim to intensive refrigeration, he will find Solvay, Dr. 

 Linde, and Prof. Onnes obstacles quite as serious as myself. 

 Further, this attempt to justify going behind my back in his 

 relations with a member of the staff of the Royal Institution, is 

 a too transparent subterfuge to require further comment. 



James Dewar, 



The Spectrum of Metargon ? 



In the account given by Prof. Ratnsay of his researches on the 

 " Companions of Argon," he has omitted to draw attention to a 

 very curious similarity between the spectrum of his new gas 

 " metargon" and the ordinary spectrum of carbon, with which 

 every student of spectrum analysis is familiar. 



The following comparison of wave-lengths will make the 

 similarity apparent. 



There are three of Ramsay's bands not included in this list, 

 but these are nearly coincident with known bands in the 

 cyanogen spectrum. 



It seems hardly credible that Prof. Ramsay has not guarded 

 against the possibility that all these bands may be due to 

 carbon, and not to a new gas ; but some explanation seems re- 

 quired, for though the coincidences in the two sets of bands is 

 not complete, there is no case known in which two different 

 elements have spectra so nearly alike as those of carbon and 

 metargon seem to be. Arthur Schuster. 



Anatomy of the Sv^rallows. 



My friend Dr. R. Bowdler Sharpe, of the British Museum, 

 has favoured me with a copy of his recent and very useful 

 memoir upon the swallows (Hirundinidie), and we find the 

 group treated under the several heads of (i)an introduction; 

 (2) geographical distribution ; and (3) the literature of the 

 Subject. In the last, the author of this contribution has evidently 

 intended to present a very complete list of the titles of works 

 that have been written about swallows, extending between the 

 years 1731 to 1894 inclusive; while in the introduction he 

 makes the statement that " The Swallows appear to us to be 

 such a well-marked and isolated Family of Passeres, that, in the 

 absence of any detailed account of their anatomy and general 

 structure, which, so far as we know, has not been attempted, 

 there reinains little for us to say." As one, perhaps, who has 

 had occasion to keep a little better track of the literature of 

 hirundine morphology, permit me to invite the attention of 

 this distinguished systematist to a memoir published by me in 

 the Journal of the Linnean Society of London for 1889 (vol. 

 XX. pp. 299-394, with 39 lithographic figures) ; he will find 

 in it, under the title of "Anatomy of the North- American 

 Hirundinidce," not only a complete account of the pterylography 

 of every species of swallow in the United States, but myological 

 descriptions of the same ; with references to their visceral 

 anatomy ; and an entire chapter devoted to the osteology of all 

 the United States genera. Not only this, but on the plates, 

 illustrating the same memoir. Dr. Sharpe will find very accurate 

 figures of the skulls (nat. size) of Propte subis, Chelidon 

 erythrogaster and Tachycineta thalcissina—aX\ important forms 



