CKLKSTIAL CHEMISTRY. 253 



twice and our own atmosphere once ; and thus any absorptive influ- 

 ence in the atmospheres of the planet and of our earih would he con- 

 siderable. l>ut the light reilerh'd I'IMMI the sky when the sun is just 

 below the horizon, having to traverse a very much greater stratum of 

 the earth's atmosphere of high density, necessarily would experience 

 a greater absorption than the light which reaches us through the com- 

 paratively thin stratum of the earth's atmosphere interposed between 

 the observer and the planet ; unless, therefore, the planetary atmos- 

 phere exerted an absorbent action, all the lines due to the action of 

 the earth's atmosphere should, in the light from Jupiter, appear 

 fainter. The results of examination showed that some were really 

 fainter, some of equal intensity, while one was much stronger ; thus 

 indicating, that some of the gases which compose the atmosphere of 

 Jupiter are the same as those which constitute the earth's atmosphere, 

 but possibly existing in different proportions. The atmosphere of 

 Mars was also found to absorb certain rays in the blue end of the 

 spectrum in a special manner ; and the loss of these is not due, more- 

 over, to mere diminution of light, but is of such a character as to 

 prove it to be due to some gaseous absorptive material. 



With regard to Venus, although as might be expected the spec- 

 trum was of great beauty, and the principal lines of the solar spec- 

 trum were well shown, no specific atmospheric lines could be traced. 



The analysis by the prism of the light of the planets, while it largely 

 confirms the astronomical doctrine of their possessing extensive atmos- 

 pheres, may, perhaps, be thought less conclusive than might have 

 been expected, but, on the other hand, it should be remembered that, 

 with the exception of Mars, telescopic observation shows that we are 

 looking not directly at the bodies of the planets, but at masses of 

 cloud suspended in their atmospheres, and reilecting the sun's light to 

 us, and therefore such light has passed through but a very small and 

 rarefied portion of such atmospheres, instead of through the lower 

 and denser portions, which we know in the case of our own aerial cov- 

 ering, to be the principal source of the specific atmospheric lines. 



The Fixed Stars. Striking as are the results obtained by spec- 

 trum analysis Avhen applied to the sun, moon, and planets, they sink 

 into insignificance when compared with the revelations afforded us of 

 the constitution of those distant bodies, the stars, and the light which 

 is thus thrown upon their structure is conclusive as to their being of 

 the same nature as our own sun ; a result which analogy had previously 

 indicated, but which had not been supported by any positive evidence. 

 It might be supposed that their distance offered insuperable obstacles 

 to such an inquiry, but spectrum analysis knows no such limits, and as 

 long as we can obtain light of an incandescent substance from a suit- 

 able source, it matters not whether it exists within a few inches of the 

 spectroscope, or at a distance of unnumbered millions of miles, the 

 result being equally certain. 



The difficulties of these observations from other causes are, how- 

 ever, according to Messrs. Huggins and Miller, very great, arising 

 principally from the extremely few occasions when telescopic obser- 

 vations with a large instrument can be carried on in England, on 

 account of the frequent atmospheric changes. The amount of work 

 done by these gentlemen during the past two years, although at first 



22 



