rj Argils and surrounding Nebula. 13 



the apparent coincidence with G F leaves, therefore, little 

 doubt that these lines in the star are due to hydrogen. 



For the yellow line there were at first three candidates. 

 D, a nitrogen line on less refrangible side of D, and the sun 

 protuberance line ; instrumental evidence has pretty satis- 

 factorily narrowed the competition by eliminating the nitrogen 

 line; whether or not the star line is due to sodium or to the 

 substance whatever it be found in sun flames, cannot at 

 present be said ; a higher dispersion, when the star has 

 sufficiently increased in brilliancy, will probably settle the 

 point. 



One of the green lines is probably due to nitrogen, for 

 although the limits of error might bring in iron as a com- 

 petitor, the iron hne in that position is not a bright one, and 

 would therefore not be seen alone of the large number of 

 lines which iron produces. 



The second green line is involved in the group 6, and may 

 be accounted for by magnesium or nitrogen ; the already 

 assumed presence of nitrogen might perhaps lead us to infer 

 that this second line is also due to it, but we know that 

 nitrogen may be certainly indicated by the chief green line 

 alone. Moreover if the conditions were such as to make 

 others of its large number of lines visible, the second green 

 one would not be the first to appear. 



On the whole, therefore, it would seem that the bright 

 lines seen in the spectrum of rj Argus, indicate the presence 

 of hydrogen, nitrogen, sodium, and magnesium. 



No dark lines have been seen with certainty, one is 

 strongly suspected in the red, and occasionally there is an 

 appearance as if the whole spectrum were crossed by a mul- 

 titude ; this is probably the case (the lines escaping our notice 

 from faintness of the general light), for no star sufficiently 

 bright to give a fairly visible spectrum has been found 

 without dark lines ; Secchi has lately seen a bright line in 

 the variable A at its maximum. In the case of T Coronse, 

 both dark and bright lines were seen by Messrs. Huggins 

 and Miller. 



As these physicists remark, it is difficult to imagine the 

 condition of a body producing light of this description ; we 

 seem driven to the conclusion that the star consists of a solid 

 nucleus, a gaseous envelope cooler than the nucleus pro- 

 ducing the dark lines, and a second envelope, hotter than 

 the nucleus, accounting for the bright ones. 



