Nov. 24, 1887] 



NA TURE 



81 



line at 495- The remaining lines du not all appear in one 

 nebula, but are associated one by one with the other three lines. 

 The lines at 500 and 495 and F have been seen in the glow of 

 the Dhurmsala meteorite when heated, but the origin of 495 

 has not yet been determined. 



The result of this comparison then is that the nebula spectrum 

 is as closely associated with a meteorite glowing very gently in 

 a very tenuous atmosphere given off by itself as is the spectrum 

 of a comet near the sun by a meteorite glowing in a denser one 

 also given off by itself when more highly heated. 



Further, it has been seen that the nebula spectrum was exactly 

 reproduced in the comets of 1866 and 1867, when away from the 

 sun. As the collision of meteorites is accepted for the explana- 

 tion of the phenomena in one case, it must, faute de inieux, be 

 accepted for the other. The well-known constituents of 

 meteorites, especially olivine, fully explain all the spectroscopic 

 phenomena presented by luminous meteors, comets, and 

 nebulce. 



I published many years £^0 an experiment in which I had 

 found that the gases evolved from meteorites under some condi- 

 tions gave us the spectrum of hydrogen and under others the 

 spectrum of carbon ; but in the globes I then used I was not 

 enabled to study the spectrum of the glow itself. 



I should add that the line at 495 makes its appearance much 

 more rarely than the one at 500, in meteorite glows. 



/3. " Stars " with bright lines. 



On reference to the maps which I exhibit to the Society, 

 though they and the discussion of them are yet incomplete, it 

 will be seen that the principal lines which are seen bright 

 in star spectra are, if we make due allowance for the 

 discrepancies likely to occur in observations attended with 

 great difficulties, lines which either have been observed in 

 the vapours and gases given off by meteorites in vacuum- 

 tubes or which we might expect to see in a combined 

 series of observations on meteorites having different chemical 

 constituents. Among these lines are Ha, H/3, H7, Ha, 464, 

 540, 570, 580, 587 ; in one case (ist Cygnus) there are lines at 

 5065 and 5268, the latter due to iron. The difficulties attend- 

 ing this part of the inquiry are referred to subsequently, and 

 it must be understood that in the absence of a detailed discussion 

 especially of the spectra of the " Novas," which I have not yet 

 completed, the opinion I express in the next part of this 

 preliminary notice with regard to bright-line stars must be 

 regarded rather as suggestions than as final conclusions. 



Discussion of the Maps showing the Bright Lines visible in 

 Stars and Nebula. 



It results from the discussion of the bright lines seen, whether 

 associated with the bright lines C and F of hydrogen or not, 



MAGNESIUM 



BARIUM 



HYDROGEN 



MET. GLOW 



NEBULA 



Map 5.— Shows the positions of three of the nebula lines as compared with well-known lines. 



that, while on the one hand we have a class of bodies — the nebukie 

 — which give us the lines visible at the lowest temperature of 

 chemical elements known to exist in meteorites, we have in the 

 other class — the "stars" with bright lines — those lines visible at 

 somewhat higher temperatures in meteorites. In the stars with 

 bright lines the two most important lines, which have been 

 separately mapped by Vogel,i occur at 540 and 582. The 

 mean readings of all the observations gives the positions 

 of these lines as 540 and 580. In an experiment on the glow 

 of a meteorite rich in manganese, the line of Mn at 5395, 

 easily seen at the temperature of the bunsen, is distinctly seen 

 in addition to the structure-spectrum of hydrogen. There is 

 reasonable ground therefore for supposing that this line, the only 

 one of the iron group of metals visible at the temperature of the 

 bunsen, may be the origin of one of the two lines seen alone in 

 the spectrum of these " stars." It will be seen that in the map it 

 has been easy to arrange all the bright lines hitherto seen in 

 stars into one order, in which we begin with this line of 

 manganese, and a line of iron seen at the temperature of 

 the oxy-coal-gas flame, the wave-length of which is 579. 

 As other lines indicating other substances are added to 

 these fundamental ones, we pass from those stars in which 

 ' Potsdam ObservatioHs, vol. iv. No. 14. 



C and F are not visible to those in which they make their 

 appearance. Here, however, it is necessary to move with 

 caution, because it may be that we are in presence of some^ of 

 the lines visible in the structure-spectrum of hydrogen. The 

 chief lines of hydrogen, as seen in the end-on tube when the 

 conditions are such that C and F are not visible, have been 

 already stated. Some of the lines observed in these stars, 

 even the one at 540, have been found to be very nearly coincident 

 with bright lines seen in the structure-spectrum, as well as with 

 lines seen in the spectra of meteorites. 



The suggestion, therefore, that some of the lines seen m 

 bright-line stars are lines of cool hydrogen must be noted, 

 although there are strong grounds for rejecting it, as will shortly 

 appear. One objection is that strong lines of the 1 1 structure 

 at 607-610 and 574 have not been recorded in star spectra with 

 those at 540 and 580. . 



In thenebul* (see Map 5) we deal chiefly with lines seen in the 

 spectrum of magnesium at the lowest temperature ; and these, as 

 far as observations go, have not yet been associated with the lines 

 at 540 and 580 to which reference has just been made, although 

 they may or may not be associated with the bright lines C and F of 

 hydrogen. In the nebulse, however, no lines coincident with the 

 lines of cool hydrogen have been observed. It will be seen, there- 



