144 LIGHT SCIENCE FOR LEISURE HOURS. 



Faint as is the light of Uranus, yet, when a telescope 

 of sufficient size is employed, the spectrum of the 

 planet is seen as a faint rainbow-tinted streak. The 

 peculiarities of this streak, if discernible, are the means 

 whereby the spectroscopist is to ascertain what is the 

 condition of the planet's atmosphere. Now, Father 

 Secchi, studying Uranus with the fine eight-inch tele- 

 scope of the Roman Observatory, was able to detect 

 certain peculiarities in its spectrum, though it would 

 now appear that (owing probably to the faintness of 

 the light) he was deceived as to their exact nature. 

 He says : ' The yellow part of the spectrum is wanting 

 altogether. In the green and the blue there are two 

 bands, very wide and very dark.' But he was unable 

 to say what is the nature of the atmosphere of the 

 planet, or to show how these peculiarities might be 

 accounted for. 



Recently, however, the Royal Society placed in the 

 hands of Dr. Huggins a telescope much more powerful 

 than either the Roman telescope or the instrument with 

 which Dr. Huggins had made his celebrated observa- 

 tions on sun and planets, stars and star- cloudlets. It 

 is fifteen inches in aperture, and has a light-gathering 

 power fully three times as great as that possessed by 

 either of the instruments just mentioned. 



As seen by the aid of this fine telescope the spectrum 

 of Uranus is found to be complete, 'no part being 

 wanting, so far as the feebleness of its light permits it 

 to be traced.' But there are six dark bands, or strong 

 lines, indicating the absorptive action of the planet's 



