The Piscian Stars. 



129 



General Characteristics of the Spectra. 



The main features of the spectra are three broad dark flutings, 

 which fade off to the violet end of the spectrum. These, as is now 

 well known, coincide with the three principal bands in the spectrum 

 of high temperature* carbon. 



The wave-lengths of the bands, and Duner's numbers, are as 

 follows : — 



No. of band. 



Duner's mean A. 



Yogel's mean \.f 



Hot carbon 

 (Angstrom) . 



6 



563-3 



563 -1 



563 -3 



9 



516 -3 



515 -9 



516 -4 



10 



472 -7 



472-9 



473 -6 



The greatest discrepancy is in the case of band 10, and this is easily 

 explained when we consider the variation of the position of the maxi- 

 mum intensity of the band to which I have previously drawn attention. | 

 At different temperatures the position of. the brightest part of the 

 band changes, and in Angstrom's measure of the carbon fluting this 

 was not taken into account. 



In addition to these principal bands, Duner mapped seven secondary 

 bands. In the Bakerian Lecture, I stated that " there is evidence that 

 some of the absorption is produced by substances which remain in the 

 atmosphere during the next stage, that of Group YII (dark bodies). ' 

 This probability is based upon the fact that some of the bands are 

 apparently coincident with bands in the telluric spectrum as mapped 

 by Brewster, Angstrom, Smyth, and others."§ 



* As in former papers, the term " high temperature," as used here, is only 

 relative, and refers to tlie spectrum of carbon which is seen in the electric arc, 

 Bunsen burner, or vacuum tube under certain conditions. The spectrum of carbon 

 at a still higher temperature consists of lines. 



t ' Potsdam Observations,' No. 14, 1884, p. 31. 

 'Koy. Soc. Proc.,' vol. 45 (1889), p. 167. 



§ Note (added 1899;. — Although my subdivision of the group into species, made 

 ten years ago, is based in part upon the secondary bands, it is not materially affected 

 by the new information as to the nature of these bands, since, as cooling goes on, 

 low temperature metallic lines would become more prominent relatively, just as we 

 might have expected the secondary bands to become stronger on the supposition 

 that they had th.e same origin as the telluric bands. 



