176 



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



should here get the second maxima of the two flntings brighter than 

 the first. 



This double effect on the carbon flutings at 564 and 51 7 of masking 

 by cool carbon and manganese was indicated in Coggia's Comet when 

 it was about a month from perihelion, and in the Comet III, 1881, 

 twelve days after perihelion, as shown below : 



Iron Absorption. 



In addition to the absorption flutings of lead and manganese as 

 indicated by their masking effects upon the carbon fluting at 564, we 

 have indications of the absorption of the iron fluting at 615. 



In Comet Wells Vogel J saw on June 2nd (the perihelion passage 

 occurring on June 10th) a bright fluting with its brightest edge at 

 613, fading towards the blue, which he attributed to hydrocarbon. 

 This was undoubtedly a contrast band due to the absorption of the 

 iron fluting at 615. Hasselberg also observed in the same comet on 

 June 5th a fluting with its sharpest edge at 61 5' 7, which he supposed 

 to be the red sodium line at 615. The iron fluting has its maximum 

 at 615, and fades away on the less refrangible side ; hence, when 

 absorbing, it will give rise to such an apparent bright band as that 

 observed by Yogel and Hasselberg in Comet Wells. 



V. THE FINAL STAGE OF HEAT PERIHELION. 



There is evidence to show that when a comet arrives at its shortest 

 distance from the sun, the mean temperature effects are exceeded ; 

 and that, speaking generally, a line replaces a fluted spectrum, and 

 we pass from a spectrum very similar to that which we ordinarily 

 get in a glow-tube to one which we cannot produce in it until we 

 employ the highest temperature. The spectral conditions brought 

 about in the comets which in our time have got nearest to the sun, 

 have been almost similar to those observed in the oxy-coal-gas flame ; 

 and the recorded observations of the spectrum show that we are 

 dealing with the lines of iron, manganese, and other substances seen 

 at that temperature, which is below that of the electric arc. 



We see in the telescope that a comet under the conditions of near 



* ' Astr. Nachr.,' vol. 85, p. 12. f ' Copernicus,' vol. 2, p. 225. 



J 'Astr. Nachr./ p. 2437. 



