174 Mr. J. N. Lockyer. On the Classification [Jan. 10. 



Fig. 



Hot carbon radiation. 

 Manganese absorption. 

 Lead absorption. 

 Integrated result. 

 Comet I, 1868. 



>. Diagram showing the result of the integration of hot carbon radiation and 

 the absorption of manganese and lead, compared with Comet I, 1868. 



persistent as the one at 517, we should still get pretty nearly the 

 same result by contrast ; that is, the darkening due to absorption 

 commencing at 545 would give rise to an apparent bright fluting at 

 546, fading away on the more refrangible side. This occurred in the 

 following comets : 



It is important to note, as a test of the validity of this explana- 

 tion, that the lead fluting never occurs without the manganese one, 

 otherwise we should get two bright maxima, one at 504, and the other 

 at 546. 



In the case of Comet III, 1881, it seems probable that both the first 

 and second flutings of lead were absorbing. Copeland (* Copernicus,' 

 vol. 2, p. 226) states that on June 25th, there was a dark band at 

 567'9. The perihelion passage of the comet occurred on June 

 16th, and the band was not seen in its spectrum on any other 

 occasion. 



There can be little doubt that the band at 567'9 was due to lead 



* ' Eo\. Soc. Proc.,' vol. 16, p. 386. 

 t ' Copernicus/ vol. 2, p. 233. 



J ' Copernicus,' vol. 2, p. 237. 



' Monthly Notices,' vol. 39, p. 420. 



