ADDRESS. lis. 



exhibit linos identical with manj- of those shown by the components of this 

 planet, as Ave proceed to the more distant appearances of the nebulas we get 

 but one or two of such lines, and we get one or two new bands not yet iden- 

 tified with any known to be produced by substances on this globe. 



Within the last year Mr. Huggins has added to his former researches 

 observations on the spectrum of a comet (comet 1 of 1S6G), the nucleus of 

 which shows but one bright line, while 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 tlie 

 author thinks it is iu 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 also is shown in some of the nebulae. 



But the most remarkable achievement by spectrum analysis is the record 

 of observations on a tcmporaiy 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 12th, it wa.s nearly equal in brilliancy to a star of the 

 second magnitude ; when observed by Mr. Huggins and Dr. MUler, May IGth, 

 it was reduced to the third or fourth magnitude. 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 different sources. 

 One spectrum was analogous to that of the sun, viz., formed by the light of 

 an incandescent sohd or Licjuid photosphere which had suffered absorption by 

 the vapours of an envelo]3e cooler tlian itself. The second spectrum consisted 

 of a few lu'ight lines, ■which indicated that the light by which it was formed 

 was emitted by matter in the state of luminous gas. They consider that, from 

 the position of two of the bright lines, the gas must be probably hydrogen, 

 and from their brilliancy compared with the light of the photosphere the gas 

 must have been at a vcrj' high temperature. They imagine the phenomena to 

 result from the burning of hydrogen 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 previously seen by 

 Argelander and Sir J. Herschel, and that it is a variable star of long or irre- 

 gular 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 important 

 if it could even have been established that it is not a near neighbour, as the 

 magnitude of such a phenomenon must depend upon its distance. I forbear 

 to add any speculations as to the cause of this most singular phenomenon ; 

 however imperfect the knowledge given us by these observations, it is a great 

 triumph to have caught this fleeting object, and obtained permanent records 

 for the use of future observers. 



It would seem as if the phenomenon of gradual change obtained towards 

 the remotest objects with Avhich we are at ijresent acquainted, and that the 

 further we penetrate into space the more unlike to those we are acquainted 

 with become the objects of our examination, — sun, planets, meteorites, earth 

 similarly though not identically constituted, stars diftering from each other 

 and from our system, and nebiilae more remote in space and differing more in 

 their characters and constitution. 



While we thus can to some extent investigate the physical constitution of 

 the most remote visible substances, may we not hope that some further insight 

 as to the constitution of the nearest, viz. our own satellite, may be given us 



