1888.] of the various Species of Heavenly Bodies. 



53 



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 dis- 

 tinguish in what follows as carbon A, there is sometimes a fourth 

 more refrangible one beginning afc wave-length 461, which is due 

 to some other molecular form of carbon; this we shall distinguish 

 as carbon B. 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. 



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 Duner's apparent absorp- 

 tion band 11. 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 brightness 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 resulting 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 continuous 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 therefore be regarded as the connecting link between the bodies 

 belonging to Group I and those belonging to the group under con- 

 sideration. 



Band 10 is the dark space between the bright carbon A fluting at 

 474 and the carbon B at 461, and can only exist so long as the carbon 

 flutings are brighter than the continuous spectrum. Duner's mean 

 values for the band are 461 — 473, and on comparing these with the 

 wave-lengths of the carbon flutings (see fig. 16) it will be seen that 

 the coincidence is almost perfect. 



There is a little uncertainty about band 11, which Duner 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. 16). This would give a band somewhat 

 broader and more refrangible than that shown in Duner's map ; but, 



