July 28, 188 1] 



NATURE 



285 



Nature (vol. xxiv. p. 124). It was, I should think, almost 

 unique in a scientific journal. It turned upon a contradiction 

 which he had detected between a statement which I never 

 made and tlie fact that he surely entertained an impression 

 that he had somewhere or other (he did not say w here) seen 

 me quoted as holding an opinion at variance with that state- 

 ment. I did not think that time would be well employed 

 in answering it. Even now he talks of his "quotation or 

 mi>quolation " ; a convenient but unusual latitude of expression 

 for a serious case of the latter of these alternatives. Really I 

 am not in the examination-room, and will not therefore attempt 

 to compress into a few paragraphs the answers I should give 

 upon intricate philosophical points, even were the questions 

 reasonably framed. Moreover I must remind Mr. McColl that 

 he does not profess to write as an impartial inquirer or critic, 

 but asked for the insertion of his letter upon the ground that he 

 conceived himself to have been attacked. I have fully explained 

 the only point upon which he had any claim to call for an answer, 

 and therefore now close the correspondence. J. Venn 



Achensee, Turol 



Jupiter 



The great red spot on the planet seems unchanged as I saw it 

 on July 8, while the north temperate zone belt (Gledhill's No. 2) 

 shows a development nearly as striking as the equatorial belts. 



Millbrook, Tuam, July 20 J. Birmingham 



New Red Variable 



This star, which I found on May 22 only 9 magnitude (see 

 Nature, vol. xxiv. p. 164), progressively increased jp to 8 m. 

 on June 6, and is now again no more than 9. Its deep crimson 

 colour is unchanged. It is 2° 5i''7 north of o Cygni, and forms, 

 with three other stars, the southern end of a little inverted and 

 irregular cross. It will probably decrease to ci mplete disap- 

 pearance, at least from telescopes of moderate power. 



Millbrook, Tuam, July 20 J. Birmingha.m 



A Fireball 



On Wednesday the 20th ult., about midnight, a house at 

 Mont Dore, in the Auvergne, was destroyed by a fireball during 

 a severe thunderstorm. My brother, who has lately arrived from 

 thence, did not see the ball himself, but his valet, an intelligent 

 Italian, saw it distinctly. He describes it as a globe of fire 

 about half a metre in diameter, which approached the house 

 obliquely, seeming to pass over a distance of 200 metres in 

 about half a minute. It entered the dour of the house and there 

 burst. My brother heard the explosion as well as his valet, and 

 describes it as a dull thud like that of a smothered blast. The 

 house, which was a wooden one, was set on fire, a child burnt 

 to death, and another inmate seriously, if not mortally, injured. 

 Several inhabitants of Mont Dore are said 1 y the valet to have 

 seen the bail, one of whom lived in the adjacent house. 



It will be interesting to readers of Nature to compare the 

 accounts given by Prof. Tait in Nature, vol. xxii. p. 409. 



19, The Boltons, S.W. John Tennant 



Meteor 



On July 23, at 7.15 p.m. (Irish railway time) a meteor passed, 

 travelling nearly from south to north, being lost In a bank of 

 black cloud. It must have been of considerable bridianey, as it 

 was quite distinct, although at the time the sun was well above 

 the horizon. July 22 from ten to fourteen brilliant red pencils 

 and thin columns of auroric lights were rising at intervals. 

 There were also auroric lights on July 23 between 11 and 12, 

 but much less brilliant. G. H. Kinahan 



Ovoca, July 24 



THE COMET 

 \X7E have received the following further comniunica- 

 ' ■' tions on this subject : — 



The following " Preliminary Note on the Photographic 

 Spectrum of Comet b 1S81," has been communicated to 

 the Royal Society by Dr. Hviggins, F.R.S. (For Dr. 

 Huggins's first note on this subject, see Nature of 

 June 30.) 



On the evening of June 24, I directed the reflector 

 furnished with the spectroscopic and photographic ar- 

 rangements described in my paper " Cn the Photographic 

 Spectra of Stars" {Phil. Trans., 1880, p. 669) to the 

 head of the comet, so that the nucleus should be upon 

 one half of the slit. After one hour's exposure the open 

 half of the slit was closed, the shutter withdrawn from 

 the other half, and the instrument then directed to 

 Arcturus for fifteen minutes. 



After development, the plate presented a very distinct 

 spectrum of the comet, together with the spectrum of the 

 star, which I have already described in the paper referred 

 to above. 



The spectrum of the comet consists of a pair of bright 

 lines in the ultra-violet region, and a continuous spec- 

 trum which can be traced from about F to some distance 

 beyond H. 



The bright lines, a little distance beyond H, with an 

 approximate wave-length from 3S70 to 3890, appear to 

 belong to the spectrum of carbon (in some fomi, possibly 

 in combination with hydrogen), which I observed in the 

 spectra of the telescopic comets of 1866 and 1S68. 



In the continuous spectrum shown in the photograph, 

 the dark lines of Fraunhofer can be seen. 



This photographic evidence supports the results of my 

 previous observations in the visible spectra of some tele- 

 scopic comets. Part of the light from comets is reflected 

 solar light, and another part is light of their own. The 

 spectrum of this light shows the presence in the comet of 

 carbon, possibly in combination with hydrogen. 



On the next night, June 25, a second photograph was 

 obtained with an exposure of an hour and a half. This 

 photograph, notwithstanding the longer exposure, is 

 fainter, but shows distinctly the two bright lines and the 

 continuous spectrum, which is too faint to allow the 

 Fraunhofer lines to be seen. 



Postscript. July 9, 1S81.— I have since measured the 

 photographs of the comet's spectrum, and I find for the 

 two strong bright lines the wavelengths 3883 and 3870. 

 The less refrangible line is much stronger, and a faint 

 luminosity can be traced from it to a little beyond the 

 second line 3S70. There can be, therefore, no doubt that 

 these fines represent the brightest end of the ultra-violet 

 group which appears under certain circumstances in the 

 spectra of the compounds of carbon. Professors Liveing 

 and Dewar have found for the strong line at the beginning 

 of this group the wave-length 38S27, and for the second 

 line 3870-5. 



I am abo able to see upon the continuous solar spec- 

 trum, a distinct impression of the group of lines between 

 G and //, which is usually associated with the group 

 described above. My measures for the less refrangible 

 end of this group give a wave-length of 4230, which agrees 

 as well as can be expected with Professors Liveing and 

 Dewar's measure 4220. 



In their paper " On the Spectra of the Compounds of 

 Carbon' {Proc. Roy. Soc, vol. xxx. p. 494), Professors 

 Liveing and Dewar show that these two groups indicate 

 the presence of cyanogen, and are not to be seen in the 

 absence of nitrogen. If this be the case, the photograph 

 gives undoubted evidence of the presence of nitrogen in 

 the comet, in addition to the carbon and hydrogen sho-wn 

 to be there by the bright groups in the visible part of the 

 spectrum. Cn this hypothesis we must further suppose 

 a high temperature in the comet unless the cyanogen is 

 present ready formed. 



I should state that Mr. Lockyer regards the two groups 

 in the photograph, and the groups in the visible spectrum, 

 to be due to the vapour of carbon at different heat-levels 

 (Proc. Roy. Soc, vol. xxx. p. 461). 



It is of importance to mention the strong intensity in 

 the photograph of the lines 38S3 and 3870, as compared 

 with the continuous spectrum, and the faint bright group 

 beginning at 4230. At this part of the spectrum, there- 



