CONTINUITY. 191 



the spectrum formed by the light of the coma is continuous, 

 seeming to show that the nucleus is gaseous, while the coma 

 would consist of matter in a state of minute division shining 

 by reflected light : whether this be solid, liquid, or gaseous is 

 doubtful, but the author thinks it is in a condition analogous 

 to that of fog or cloud. The position in the spectrum of the 

 bright line furnished by the nucleus is the same as that of 

 nitrogen, which line is also shown in some of the nebulae. 



But the most remarkable achievement by spectrum ana- 

 lysis is the record of observations on a temporary star which 

 has shone forth this year in the constellation of the Northern 

 Crown, about a degree S.E. of the star e. When it was first 

 seen, May 12, it was nearly equal in brilliancy to a star of the 

 second magnitude ; when observed by Mr. Huggins and Dr. 

 Miller, May 16, it was reduced to the third or fourth magni- 

 tude. Examined by these observers with the spectroscope, it 

 gave a spectrum which they state was unlike that of any 

 celestial body they had examined. 



The light was compound, and had emanated from two dif- 

 ferent sources. One spectrum was analogous to that of the 

 sun, viz. formed by the light of an incandescent solid or liquid 

 photosphere which had suffered absorption by the vapours of 

 an envelope cooler than itself. The second spectrum consisted 

 of a few bright lines, which indicated that the light by which 

 it was formed was emitted by matter in a state of luminous 

 gas. The observers consider that, from the position of two of 

 the bright lines, the gas must probably be hydrogen, and from 

 their brilliancy compared with the light of the photosphere 

 the gas must have been at a very high temperature. They 

 imagine the phenomena to result from the burning of hy- 

 drogen with some other element, and that from the resulting 

 temperature the photosphere is heated to incandescence. 



There is strong reason to believe that this star is one pre- 

 viously seen by Argelander and Sir J. Herschel, and that it is 

 a variable star of long or irregular period ; it is also notable 

 that some of its spectrum lines correspond with those of several 

 variable stars. The time of its appearance was too short for 

 any attempt to ascertain its parallax ; it would have been im- 

 portant if it could even have been established that it is not a 



