46 SPECIAL RESULTS IN THE URANOLOGICAL 



of the year, particular lines were wanting ; but Brewstet 

 has shewn that this is a consequence of the different heighr 

 of the sun, and the different absorption of the rays of light 

 in their passage through the atmosphere. In the coloured 

 spectra given by the reflected light of the Moon, Yenus, 

 Mars, and the Clouds, we find, as would no doubt have 

 been expected, all the characteristics of the solar spectrum. 

 On the other hand, the dark lines of the spectrum of Sirius 

 differ from those of Castor or of other fixed stars. Castor 

 himself shows other lines than those shown by Pollux and 

 Procyon. Arnici has confirmed these differences, which 

 had already been indicated by Fraunhofer, and has called 

 attention to the fact that, in fixed stars of at present equal 

 and perfectly -white light, the dark lines are not the same. 

 There still remains here a wide and important field for 

 future research, ( 96 ) in order to separate what is certain 

 from what is rather to be termed accidental dependent on 

 the absorbing effect of the atmosphere. 



There is another phenomenon deserving to be here noticed, 

 in which the specific character of the source of light has a 

 powerful influence. The light of glowing solid bodies and 

 that of the electric spark show great variety in the number 

 and position of Wollaston's dark lines. According to Wheat- 

 stone's remarkable experiments with revolving mirrors, the 

 light of friction-electricity appears also to have a velocity 

 greater than that of solar light, in the ratio of at least 3 to 2 

 (or fully 83920 geographical miles in a second of time). 



A new life has animated all departments of optics from 

 the time when (in 1808) the reflection of the light of the 

 setting sun from the windows of the Palais du Luxembourg 

 accidentally led the acute Malus to the important dis- 



