February 21, 1895] 



NA TURE 



389 



a glass vessel ? In his letter of February 14, Prof. Dewar 

 tells us that by mean'; of the copper coil apparatus of 1886 

 "liquid oxygen was made and decanted or transferred from 

 the vessel in which it was liquefied to another by means of a 

 valve, and thereby rendered capable of use as a cooling agent." 

 Why, then, did he not use the liquid oxygen as a cooling 

 agent? It is strange that seven years after this, when Prof. 

 Dewar wished to " prosecute research at temperatures 

 approaching the zero of absolute temperature," he says he had 

 " no recorded experience to guide [him] in conducting such 

 investigations." Had he forgotten his own apparatus with its 

 copper coil 45 feet long ? 



Prof. Dewar's apparatus of 1886 must have been peculiar ; in 

 one sentence in his letter of .February 14, its deviser speaks of 

 it as "entirely different in type from the crude plan Olszewski 

 adopted in iSgo," and in another sentence he assures us it was 

 "practically identical in principle with that used in Cracow in 

 1890." 



The apparatus of 1886 succeeded, in Prof. Dewar's hands, in 

 producing solid oxygen ; why have we heard nothing of that 

 solid oxygen? Determinations of some of the constants of that 

 substance would be interesting and important. 



I must beg attention to an instance of Prof. Dewar's bold- 

 ness. In 1SS3 Mes-rs. Wroblewski and Olszewski liquefied 

 oxygen, and other gase>, in a strong glass tube ; in 1SS4 Prof. 

 Dewar repeated some of the experiments of the Polish Pro- 

 fessors, using, as they had done, a strong glass tube, but 

 adapting some parts of their apparatus so as to make it " for 

 the purpose of lecture demonstration . . . more readily and 

 quickly handled"; in 1890 Prof. Olszewski described an 

 improved and enlarged inHrument, based on that described by 

 -his colleague and himself in 1SS3, wherein the liquefaction was 

 effected in a steel cylinder. Vet, in his letter to Nature of 

 February 14, Prof. Dewar says " replace the glass tube in «/f 

 apparatus of 18S4 by a small steel cylinder, and attach to its 

 lower end a narrow copper tube with a stopcock, and 

 the Olszewski apparatus of 1S90 is produced." (The italics are 

 mine.) 



(4) As regards Prof. Dewar's joint claim to priority in the 

 determination of the refractive index of liquid oxygen, I admit 

 he is tight and I was wrong. I was misled by the date at the 

 beginning of the paper which contains the earliest measure- 

 ments by Messrs. Olszewski an 1 Witkowski of the refractive 

 index of liquid oxygen. The paper is headed Extrail tin 

 BulUlin de I' AcaJhnic lies Sciences de Cracovie, Octohre 1 89 1. 

 At the end of the paper is the date 15 Juillet 1S92 ; this, and 

 the footnote, quoted by Prof. Dewar, make it evident that 1891 

 at the beginning of the paper is a printer's error for 1892. I 

 am sorry I made this mistake. Nevertheless, consilering that 

 Olszewski's quantitative experimenis on the optical properties 

 of liquid oxygen were bjgun in 1887 ( IVicd. Ann. xxxiii., 570), 

 and were continued in January 1891 (ibid, xlii., 633), I hold I 

 was justified in referring to Prjf. Dewar's experiments on the 

 optical properties of liquid oxygen as " mainly repetitions of 

 the work of Olszewski and Witkowski." 



Tow.ards the end of his letter Prof. Dewar refers to a quota- 

 tion I made from one of his lectures {" Having no recorded 

 ■experience to guide us . . . ") ; he follows mv quotation (of 

 which he gives only a part) by another to the effect that " the 

 necessity of devising some new kind of vessel for storing and 

 manipulating exceedingly volatile fluids, like liquid oxygen and 

 liquid air, became apparent when the optical properties of the 

 bodies came under examination. " I had expressed admiraton 

 "of the skill which produced" Prof. Dewar's new vacuum 

 receivers. Prof. Dewar now tells us that when he prefaced 

 his account of the making of these receivers by the sweeping 

 assertion that he had no experience to guide him in conducting 

 investigations at very low temperatures, he did not mean what 

 he said ; it was merely his way of saying that the vacuum 

 receivers he was about to describe had not been made before. 

 It was not I who made, it was Prof. Dewar himself who has 

 made, a "glaring misrepresentation of the meaning" of his 

 own words. 



Prof. Dewar lays no stress, in his letter, on his own experi- 

 ments on chemical action, phosphorescence, &c., at very low 

 temperatures. It is these experiments, I suppose, that are 

 referred to when he speaks of "thro*ing his bread upon the 

 waters " ; or does he abandon them as trifling, in that strange 

 sentence — " Have I ever suggested that Prof. Olszewski was 

 anticipated, or attempted to taise any question of priority ? " ? 



NO. I ■^2 1, VOL. 51] 



Prof Dewar hides the essential questions in a 

 mist of words. If he has made marked improve- 

 nienls in the methods of liquefying and manipu- 

 lating the more permanent g.ases (besides his 

 invention of vacuum receivers) ; if he has con- 

 ducted original, accurate, and thorough investi- 

 gations into the properties of the liquefied gases, 

 where are the accounts of this work to be found ? 

 Every student of the subject knows he can lay 

 his finger on the work of Olszewski, and also on 

 that of his deceased colleague Wroblewski ; and 

 he knows that work to be thorough, accurate, and 

 important. But where can there be found some 

 distinct account of the scieniific work in con- 

 nection with the liquefaction of the more per- 

 manent gases that is attributed to the Fullerian 

 Professor at the Royal Institution? 



I asked, and I siill ask, for an "instant and 

 serious consideration" of the whole matter 

 brought forward in these letters by "those who 

 are truly interested in the advance of science, 

 and are jealous of the good name of the scientific 

 men of this country." 



M. M. Pattison Muir. 



Cambridge, February 17. 



Argon. 



The beautiful research of Lord Rayleigh and 

 Prof. Ramsay has proved up to t'ne hilt that in 

 argon they have discovered an unknown gas 

 which is remarkable for some of its physical 

 properties, and especially for its extraordinary 

 chemical inertness. 



Among the interesting questions which have 

 been raised, but not fully solved, a-e : Is argon 

 an elementary Viody ? If so, how does it stand 

 related to the other elements? 



There are some who advocate its being an 

 allotropic form of a previously known element, 

 just as ozone is allotropic oxygen ; but it has 

 not yet been produced from, or resolved into, 

 nitrogen or any other element ; and, until that 

 should happen, it has the full right to take rank 

 as a new element. 



At first sight the fact of its giving two different 

 line spectra under different circumstances might 

 favour the idea of its being resolved into two 

 bodies; hut the fact that these two very com- 

 pound line spectra have twenty-six lines in com- 

 mon, which are not all of them among the 

 strongest lines, appears to me an argument for 

 the fundamental unity of the substance. 



If argon be an element, what is its place in 

 Mendele'eff's table? This is at present agitating 

 the minds of chemists and physicists. The 

 specific gravity of the gas would lead to an 

 atomic weight of close upon 20 ; but it is 

 argued from the velocity of sound through it 

 that it is a monatomic gas, and therefore close 

 upon 40. Now, if 20 be the atomic weight, it 

 will fall in admirably with the periodic law ; if 

 40, it will be perfectly inconsistent with it. The 

 argument in favour of 20 is at least five-fold : — 



(i) It will fill an existing vacancy in Men- 

 dele'eff's arrangement ; that at the top of the 

 eighth column. This is the first "even " series; 

 and it should be remembered that the later 

 "even" series in that last column are repre- 

 sented by the iron, palladium and platinum 

 groups of metals; the "uneven" series being 

 as yet unrepresented. 



(2) It will follow the periodic law in regard 

 to its melting point. That should be very low, 

 like nitrogen, oxygen and fluorine ; and so it is. 



(3) It will follow the law in regard to its 

 atomic volume. That is small ; and so it should 

 be by analogy. 



(4) A great characteristic of argon is its not 

 forming stable compounds with other bodies, at 

 any rate at a temperature high above its boiling 



