396 Celestial Chemistry. 



nous bodies themselves, and not, as might have been expected, 

 to our own atmosphere. 



Although a very bright star, the observations of Sirius are 

 extremely difficult, from its low altitude in this country, by 

 which it is brought within the densest and most impure part 

 of our atmosphere. Sodium, magnesium, hydrogen, and pro- 

 bably iron, have been found by coincidences, and a photograph 

 of the spectrum was obtained on wet collodion, but owing to 

 the combined difficulties of the experiment, the lines could not 

 be traced in the picture. It is, however, believed by the 

 observers that further experiments will result in this important 

 object being attained, and the facility which will then be afforded 

 of comparison of the more refrangible and less luminous parts 

 of the stellar spectra, when thus self-registered, with existing 

 metallic charts, must be obvious. 



Vega (a Lyras) has a spectrum full of lines. Those of 

 sodium, magnesium, and hydrogen have been identified. 

 Capella certainly contains sodium. This star was photographed 

 at the same time as Sirius. In the spectrum of Arcturus thirty 

 lines were measured — that of sodium is present ; but in this 

 and all the other stars referred to, the work is still incomplete, 

 although in progress. Pollux shows sodium, magnesium, and 

 iron ; a Cygni and Procyon sodium ; and the following stars 

 have been observed, and their lines partly measured., but 

 metallic comparisons have not yet been made. Castor, e, £, and rj 

 Ursas Majoris ; a and e Pegasi ; a, @, and 7 Andromedas, the 

 last an interesting spectrum ; Kigel, full of lines ; i) Orionis ; 

 a. Trianguli ; 7 and e Cygni ; a, /S. 7, e, and 77 Cassiopeiae ; 7 

 Geminorum ; /3 Canis Majoris; /S Canis Minoris; Spica; 

 7, S, and e Virginis ; a Aquilas ; Cor Caroli ; /3 Aurigas ; 

 Pegulus ; /3, 7, S, e, £, and rj Leonis. 



One of the most important and interesting deductions 

 which the observers, whose work we have been discussing, 

 draw from their results, is connected with the origin of the 

 colours of the stars. That there is great variety of tints 

 among these bodies is well known ; white, yellow, and red stars 

 are the most frequent, whilst in double stars the contrasted 

 colours are often green or blue. The source of the light of the 

 stars, as well as of that of the sun, must be a solid or liquid body 

 in a state of incandescence, as only such bodies, when raised 

 to a high temperature, give a continuous spectrum. In the 

 case both of the sun and stars, this continuous spectrum be- 

 comes crossed by dark bands, which are produced by the 

 absorbing power of the constituents held in a vaporous form in 

 the investing atmospheres. These atmospheres vary in chemical 

 constitution according to the elements composing the star, and 

 should the dark lines produced by the absorptive power of the 



