256 



NATURE 



[Jli.v 1 1, 1895 



not to be compared with the tluonr-tcnLc utvci'i m i* lin. mi>- 

 charge in an}' known gas. The yellow and green lines can be 

 seen and measured in the s|>eclroscope in full daylight. 



The photographs give the following lines wavelengths. X X 

 579. 577 and 546; 456, 405, 354. 313 and 312 (ultra-violet): 

 one can see two \iolet lines besides, 420 and 416, scarcely 

 visible, and the lines 385 and 35S. 



The s[>ectrum observed at the end of fifteen hours was 

 maintained during thirty consecutive hours. 



.\lthough advantage has l>een taken of photography for the 

 r^istration of these phenomena, care must be taken not 

 to confound such eftVcts, observed in the daytime and under 

 norm.il pressure, with the glows developed by the discharge in 

 very rarefied gases, such as are generally observed in a si>eclro- 

 scope. 



The meaning of these lines is as follows : 

 The line A 579 is simply one of the lines visible in daylight, 

 ami under normal pressure, which I had described in Comptcs 

 rtiidiis (t. cxx. p. 800). ixjinting out that it was probably double. 

 The lines AX 580- 1 .and 577 'I descrilied in the spectrum of rarefied 

 argon, by Mr. Crookes (Jan. 24, 1895), rnust be comjiared with 

 them. 



Line X 546 is also described (547) in my preceding note, and 

 answers to a strong line 545 "6 attributed to the spectnmi of rarefied 

 argon by Mr. Cnvokes. M. I)i— landrcs h.as recognised the same 

 lines in the sjicctrum of rarefied argon, which he had prepare<l 

 by means of lithium. I have verified, by juxtaposition, the 

 coincidence of the last line of rarefied argon with that of my 

 tube. 



I have also announced line 436, found again in the photo- 

 graph, and very close to 434"5 of rarefied argon (Crookes). The 

 lines 420 and 416 coincide with the very strong lines 420"! — 

 4I9'8 and 4I5'<)6 of rarefied argon (Crookes). The line 405 can 

 lie Identified with the line 404-4 of Crookes (argon). I have 

 verified the coincidence. Line 385 coincides with Crookes" 

 strong line 385-I5 (argon). Line 354, with a group of strong 

 lines at 3547 — 353"4 of argon (Crookes). Line 35S with 

 CrtKikes' group of strong lines 3587 — 357'S (argon). 



K 5l6'5 is a hydrocarlion Kand ; 313 and 312 are the lines of 1 

 the va|K)ur of mercury vajxiur. I 



None of these lines, as I have already stated, coincide either I 

 with the line of helium (5S7'5I or with the principal line of the I 

 aurora Ijorealis (557), although the latter is very near to a .strong 

 line of argon ( 5557). If the .actual fluorescence is not the same 

 .as that of the aurora borealis, still its development, and the 

 nearness of the preceding lines, establish a probalile relation 

 lietwcen this meteor and the existence of argon in the 

 atmosphere. 



Here a very imp<jrtant circumstance presents itself. While 

 examining the table of argon lines, given by Mr. Crookes, 

 certain lines were seen to coincide with certain lines of the va|xnir 

 of mercury. The same coincidence is found in the straight lines 

 visible in daylight, under the normal pressure, in the fluorescence 

 developed during the reaction of lien^enc on argon. Such are, 

 according to M. Deslandres, the yellow lines 579 and 577 : al>o 

 the very cliar-icleristic green line 546, the blue line 436, the 

 violet line 405, the ultra-violet line 354. On the contrary, the 

 lines 420, 416, 385, 358, l>eloni.' to argon only, the lines 313 

 and 312 tomcrcur)-. 



.\I. Deslandres attributes the common lines lo the presence of 

 the vajxiur of mercury, either in rarefied argon, or in the 

 fluorescent light obtained with bcn/ene umler normal pressure. 



Nevertheless, as no known gas gives this fluorescence, or these 



bnes. under normal pressure in (.jierating with mercury, it is not 



|«.s-ible lo explain their production merely by the presence of 



this vaixjur alone. Otherwise it would not Ik: un<ler.stoiKl why 



thry did not show themselves in pure argon, in the presence of 



1, final pressure, and th.it Ihcy would not ppKluce 



Ihe first UKpments of rlischarge, either with 



■ . .nth lien/ene, or with sulphide of carbon over 



with nitrogen under the s.-imc conditions, where it 



•li I . [,/. ijf and sulphide of carlxin. f)n the con- 



Willi ■d with lien«ne. they develop themselves 



ii ilv i..l hours, anil after the progressive trans- 



••.u/ene into a M-rieM>f romixiunds more and 



It ii one of these roni|Miunds which, imme- 



' ■ " 'oth with argon and mercury, 



ir rc.mmon character of mon- 

 ■ begins when there still exists 

 |unntily ot li<|iiid licnAcnc in the lulx.-s ; it is (hen 

 ' d by a diminution of gaseous volume. 



NO. I 34 I, VOL. 52] 



Irary 



"nlv 



1 iii> !uii'iL->^ L-iKc L. 'Utituicsa V cry long lime, even after there 1> 

 no apivirent benzene; at last the fluorescence ceases lo be visible in 

 the daylight, in consequence of the very prolonged action of the 

 discharge, which at last extinguishes the green tint, and brings 

 back this gaseous system to a glow analogous to that of ordinary 

 gases, this happens doubtless in consequence of the destruction 

 of the last traces of benzene (or the products of intermediate 

 condensation), which maintained the equilibrium of the dissocia- 

 tion of the system. 



( )nce the green fluorescence is well established, the comixjuiuls 

 which develop it are stable Viy themselves ; even after twelve 

 hours" break, if the apparatus h.as not l>een disturbed, it suftices 

 to pass the discharge, to see that the fluorescence re-establishe.s 

 itself vvith all its brilliancy in an instant. But it ceases so soon 

 as the electric current is stopped. 



But if the gas is separated from the condensed matter, the 

 phenomenon cannot be immediately produced, either on the one 

 or on the other. The gas alone, subjected to the action of thedis- 

 charge, puts on almost immediately a special violet fluorescence, 

 visible in darkness, and which generally precedes the develop- 

 n>ent of the beautiful green fluorescence. Nevertheless this does 

 not reproduce itself then, which seems to indicate that the con- 

 densed matter contains one of the products necessary to the 

 equilibrium. If, on the other hand, new argon is reintroduced 

 into the tulic containing the condensed matter (free from visible 

 benzene), the green fluorescence does not reproduce itself: Imt 

 after some time, near the surface of the mercury, there appears, 

 where the sirarking is most intense, a local green lint, which gives 

 the special lines, although not ver>- distinctly. This appearance is 

 doubtlcssdue to the existence (or to the regeneration) of a trace 

 of benzene, more or less modified. In fact, if a few more drops 

 of liquid benzene are added in the tube which contains the 

 condensed matter and the new argon over mercury, half an 

 hour is enough to make the green tint reappear in all its 

 brilliancy. Hut if there is an excess of lienzene, several hours are 

 required for its reappearance. 



These various observations, added to the limited character of 

 the absorption of argon, demonstrate the existence of a com- 

 plex state of equililirium. in which at the same time argon, mer- 

 cury, and the elements of benzene, or rather a compound con- 

 densed from it, are concerne<l. 



T 



II IE REFORM OF OCR WEIGHTS ANH 

 MEASURES. 



'111. Report of the Select Committee appointed to inquire 

 whether any, and what, changes in the present system of 

 weights and measures should be adopted, has been published as 

 a Parliamentary paiier. 



Kvidence from witnesses representing oflicial, commercial, 

 manufacturing, Irade, educational, ami professional interests was 

 received by the Committee, and numerous corporations. School 

 Boards, and other public iKidies sent resolutions in favour of the 

 adoption of the metrical system. 



.\ll the witnesses expressed a strong opinion .as lo the compli- 

 cated and unsatisfactory condition of the present weights and 

 mea.sures in use. and of the distinct and serious drawback ti> 

 British commence, especially in the foreign tnule. which this 

 system entails, difl"ering as it does from the system ( met rical ) now 

 adopted by almost every Luropcan nation, as well asbyiarthe 

 majority of non-l-".uro|x.'an countries with which this kingdom 

 trades. The evidence also showed that the home trade -.vould 

 be benefited if more simple and uniform standards of weights 

 and measures than those now existing were adopted. 



.Moreover, strong evidence was brought forward as to the 

 -.erious loss of time incurred by Knglish sclioiil-childreii In having 

 lo learn the complicated system of tables of existing weights and 

 measures, and the urgent need of the adoption of a sliiiplei 

 system. It was .statedihat no less than one year's school lime 

 would lie saved if the metrical system were taught in place of 

 that now in use. ■ t ■ 



IMdence from competent witnesses proved to the satislaclion 

 of the Committee that a compulsor)- change from an old .and com- 

 plicated system to Ihe melrical had taken jilace in tlerinany, 

 Norway and Sweden. Switzerland, Italy, and many other 

 Kuropean countries without serious opposition or inconvenience : 

 that this change was carried out in a comparatively .short period ; 

 and thai as s.M.n as the simple character of the new system was 

 understi«.d it was appreci.ated by all clas.ses of the population. 



