1889.] of the various Species of Heavenly Bodies. 



165 



flutino- of cool carbon at 483. This observation was made on the 



5 



25th of March. 



III. COMETS ABOUT MEAN DISTANCE 2ND STAGE OF HEAT. 



When meteorite dust is more strongly heated in a glow tube, the 

 whole tube, when the electric current is passing, gives us the fluted 

 spectrum of carbon, and other bright metallic flutings are added to 

 that of magnesium at 500. Among those metallic flutings which are 

 first added may be chiefly mentioned Mg 5210 and Mn (1) 558. 



Both these as well as the high- temperature fluting of carbon, have 

 been seen in comets, and I now proceed to give the details of the 

 observations. 



Magnesium Radiation, 5210. 



"While comets at their lowest temperatures give the magnesium 

 fluting at 500, as they approach perihelion, to this is added the fluting 

 at 5210. The result when this is seen with the 517 fluting of carbon, 



Hot carbon radiation. 

 Magnesium n dial ion. 

 Integrated result. 

 Comet d, 1880. 



FiG. 1. Diagram showing the result of the integration of tlie hot carbon fluting at 

 517 and the magnesium fluting at 521, compared with Comet d, 1880. 



which is always present, is an apparent displacement of the carbon 

 fluting to a less refrangible position as shown in fig. 1. This probably 

 occurred in the following comets : 



* ' Astron. Soc. Monthly Notices,' vol. 41, p. 53. 



t Pamphlet. ' Mem. de 1'Acad. de St. Petersbourg,' vol. 28, No. 2. 



