3* 



NATURE 



[May 10, 1888 



thing happens at the more refrangible edge of the other 

 absorption of Mg at 500, as DuneYs figures show. 



Less refrangible edge. 



5502 ... . 

 SOI 

 S03 ••• • 

 S05 ... • 



More refrangible sharp edge. 

 496 in a Herculis. 

 496 in p Persei. 

 496 in R Leonis Min. 

 496 in /3 Pegasi. 



If this explanation of the rigidity of the less refrangible 

 edge may be accepted, it is suggested that the rigidity of 

 the end of band 8 at 496, near the nebula line 495, seems 

 to indicate that we may have that line as the bright, less 

 refrangible, boundary of another radiation fluting. 



The fluting at 5 1 7 is the chief radiation fluting of carbon. 

 The next more refrangible one, which would be most easily 

 seen, as the continuous spectrum would be less bright in 

 the blue, has its less refrangible and brightest edge at 474. 



This in all probability has been seen by Dune'r, though, 

 as before stated, there is here a discrepancy between his 

 maps and his text. It lies between his dark bands 9 and 

 10, the measurements of which are as follow : — 



Band 9 

 Band 10 



Less refrangible edge. 

 482 ... 



484 ... 

 472 ... 



474 ... . 



More refrangible edge. 



476 in a Orionis. 



477 in & Pegasi. 

 460 in a Orionis. 

 462 in Herculis. 



It is not necessary for me to point out the extreme and 

 special difficulty of observations and determinations of 

 wave-lengths in this part of the spectrum. Taking this 

 into consideration, and bearing in mind that my observa- 

 tions of the chemical elements have shown me no other 

 bands or flutings in this region, I feel justified in looking 

 upon the narrow bright space between bands 9 and 10 as 

 an indication of another carbon fluting — the one we 

 should expect to find associated with the one at 517, with 

 its bright edge at 473 instead of 476, where DuneYs 

 measurements place it. There is a bright fluting in this 

 position in Nova Orionis. 



I shall refer to both these points later on. 



The third fluting, the carbon one with its brightest edge 

 at 564, is certainly also present ; though here the proof 

 depends upon its masking effect, and upon the manner 

 in which this effect ceases when the other flutings narrow 

 and become faint. 



In addition to these three flutings of carbon, which we 

 shall distinguish in what follows as carbon A, there is 

 sometimes a fourth more refrangible one beginning at 

 wave-length 461, which is due to some other molecular 

 form of carbon. It extends from wave-length 461 to 451, 

 and, as we shall presently see, it is this which gives rise 

 to the apparent absorption band No. 10 in the blue ; 

 this we shall distinguish as carbon B. 



It is very probable also that in some cases there is, in 

 addition to carbon A and carbon B, the hydrocarbon 

 fluting which begins at wave-length 431, the evidence of 

 this being DuneYs apparent absorption band 1 1. It may 

 be remarked here, that although most of the luminosity 

 of this fluting is on the more refrangible side of 431, 

 there is also a considerable amount on the less refrangible 

 side. 



With regard to bands 9, 10, and 11, then, there is little 

 doubt that they are merely dark spaces between the 

 bright blue flutings of carbon, and that whether they are 

 seen or not depends upon the relative brightnesses of" the 

 carbon flutings and the continuous spectrum from the 

 incandescent meteorites. When the continuous spectrum 

 is faint, it will not extend far into the blue, and the re- 

 sulting dark space between the bright carbon A fluting at 

 474 and the end of the continuous spectrum is the origin 

 of the apparent absorption band 9. When the con- 

 tinuous spectrum gets very bright, band 9 should, and 

 does, disappear. On reference to the maps of the 

 spectra of the "stars" with bright lines, it will be seen 

 that the broad apparent absorption band in the blue 



agrees exactly in position with band 9, and it undoubtedly 

 has the same origin in both cases. This band may there- 

 fore be regarded as the connecting link between the 

 bodies belonging to Group I. and those belonging to the 

 group under consideration. 



Band 10 is the dark space between the bright carbon 

 A fluting at 474 and the carbon B at 461, and can only 

 exist as long as the carbon flutings are brighter than the 

 continuous spectrum. DuneYs mean values for the band 

 are 461-473, and on comparing these with the wave- 

 lengths of the carbon flutings (see Fig. 10, which will be 

 given in the next instalment) it will be seen that the 

 coincidence is almost perfect. 



There is a little uncertainty about band 11, which 

 Dune'r was only able to measure in one star, but it very 

 probably has its origin in the dark space between the 

 bright carbon B fluting and the hydrocarbon fluting at 

 431 (see Fig. 10). This would give a band somewhat 

 broader and more refrangible than that shown in DuneYs 

 map ; but, as already pointed out, great accuracy in this 

 part of the spectrum cannot be expected. 



Chemical Substances indicated by the Absorption Flutings 

 and Bands. 



I may state that I have now obtained evidence to show 

 that the origin of the following absorption flutings is 

 probably as under : — 



Wave-length of 



less refrangible 



end, given by Duncr 



as measured in 



a Orionis. 



... 628 



- 595 

 ... 564 

 ... 550 

 ... 526 



- 5i7 

 ... 495 



These flutings are characteristic of the whole class, 

 and DuneYs catalogue consists chiefly of a statement of 

 their presence or absence, or their varying intensities, in 

 the different stars. 



He gives other bands and wide lines which he has 

 measured specially in a Orionis. I have also discovered 

 the origin of the majority of these. They are as 

 follows : — 



Lines 



Band 1, which extends from wave-length 649^5 to 663*8, 

 has not yet been allocated. 



Tests at our Disposal. 



In order to prove that my explanation of the nature of 

 these celestial bodies is sufficient, a discussion of the 

 individual observations of them, seeing that differences in 



1 Means strongest fluting. 



2 The sec jnd Pb band has been seen in a Scorpii and a Orionis. Owing 

 t > an error in the map in the former paper, this fluting was ascribed to zinc. 



3 This is the second brightest band, wave-length 525. The first, at wave- 

 length 515, is masked by the radiation fluting at 516. 



4 This is not given by Duner. It would be masked by the Mn fluting in the 

 star. I have inserted it to show that we could not be dealing with the 3rd 

 fluting of Cr at 536 if we could not explain the apparent absence of the 

 2nd. 



5 In the early stages this band is masked by the vivid light coming from 

 the carbon in the interspaces. 



