1880.] 



On the Spectra of Meteor-swarms. 



389 



The wave-lengths and origins of the lines and flutings recorded in 

 the observations are shown in the following table : 



VI. Criteria between Groups III and V as deduced from the 

 Observations. 



The general conclusion to be drawn from the observations is that 

 there are several lines in the spectra of stars on the ascending side of 

 the temperature curve, which do not occur in stars with a spectrum 

 resembling that of the Sun, which must lie on the descending side of 

 the curve, as we know it to be cooling. 



Some lines, such as F, 6, D, and E, are common to both sides of the 

 curve, though the relative intensities are slightly different. 



The principal criterion in the visible part of the spectrum is the 

 double line about wave-length 540, which, with the two iron lines 

 E (5268) and 5327, forms the trio referred to in the observations. 

 Each member of the trio is seen to be double when a high power is 

 used. These three equidistant lines, which are of nearly equal inten- 

 sities, are well seen in Aldebaran and several other stars, but are not 

 seen as such in either Arcturus or Capella. 



Tn Arcturus and Capella, as in the Sun, there is a double line 

 (5403, 5404' 9) which makes an almost equidistant trio when com- 

 bined with E and 5327. Direct comparison with Group III stars, 

 however, shows that the lines are not coincident. On one or two 

 occasions the spectra of some stars of Group III were compared with 

 the spectrum of the Moon ; in the absence of the- Moon, compari- 

 son was made with Arcturus or Capella. A comparison of the 

 Group III line with the Mn line at 540 referred to in previous papers 

 shows a perfect coincidence with the dispersion employed ; and since 

 both are double we are driven to the conclusion that the 540 line 

 in stars of Group III is due to manganese. Again, the double in 

 Group V is considerably weaker than E, whereas that in Group III 



