138 



Sir Norman Lockyer. 



of carbon. This was the information wanted, but more recently 

 Professor Hale has published photographs of the spectra of 280 Schj., 

 273 Schj. (19 Piscium), 132 Schj. (U Hydrse), and 152 Schj., taken 

 with the aid of the Yerke's telescope at Chicago, and showing a wealth 

 of fine detail."^ The dark line spectrum is very marked, and the 

 details of the carbon bands themselves are clearly revealed. Besides 

 these, there are certain bright places in the spectrum which Professor 

 Hale has been led to believe are true bright lines, and he mentions that 

 Professor Keeler has arrived at the same conclusion as a result of his 

 observations with the Lick refractor. 



Duner appears to have continued his observations of this group of 

 stars after his removal from Lund to Upsala, and he states that with 

 the Upsala refractor he was able to see more detail, and could detect 

 without difficulty bright lines in the spectra of various stars of the 

 group, t 



The Question of Bright Lines. 



As I have already pointed out. Professors Hale, Keeler, and Duner 

 consider that there are bright lines in some of these spectra, but I 

 must confess that the published photographs do not convince me upon 

 this point. In the plate which accompanies Professor Hale's paper of 

 April, 1899,1 the spectra of four stars are shown, namely, 280 Schj., 

 273 Schj., 132 Schj., and 152 Schj. A study of these photographs 

 shows that the supposed bright lines are involved in the carbon ab- 

 sorption bands in the yellow green, and occur where there is reduced 

 absorption, on the less refrangible sides of the dark flutings. 



This at once led me to suppose that they could not be real bright 

 lines, but simply places in the continuous spectrum where there is least 

 absorption. These supposed bright lines are most marked in 152 Schj., 

 and there is no suggestion of them in 280 Schj., while I think few 

 would be disposed to suggest their presence in 273 Schj. and 132 Schj. 

 without having 152 Schj. as a guide. Nevertheless, in these inter- 

 mediate stars there are certainly bright ]places corresponding in posi- 

 tion with the "bright lines" in 152 Schj., the principal one being at 

 A 5592. So far as appearances go, the greater apparent intensity of 

 the bright line in 152 Schj. appears to be due to the introduction of a 

 strong absorption line on the less refrangible side. 



In another paper§ Professor Hale reproduces photographs of 152 

 Schj. in which the contrast has been increased by photographic means, 

 so that the whole spectrum appears to consist of bright lines, rather 

 than dark ones. 



* ' AstropTiys. Journ.,' vol. 8, pp. 238-9 ; vol. 9, p. 271 ; vol. 10, p. 110. 



t * Astrophys. Journ.,' vol. 9, p. 121. 



X ' Astropliys. Journ.,' vol. 9, p. 271. 



§ ' Astropbys. Journ.,' vol. 10, August, 1899, p. 108. 



