34 



of chemists, and both classes of scientists now constantly 

 resort to spectral analysis. If a chemist is unable to 

 dissolve a body into its constituent elements though its 

 unity arouses suspicions, he places a piece of the sub- 

 stance on a platinum plate or wire, heats it in the 

 lamp, and studies the result in the spectroscope. If the 

 burning substance yields a single line it is a chemically 

 homogeneous substance, but if, on the other hand, two 

 or three lines make their appearance, or one main line 

 with branches, the chemical elements of the body are 

 compounded, and those of these lines which coincide 

 with lines already investigated in the solar spectrum, 

 belong to those gases, metals or minerals which scien- 

 tific men in their researches have already examined. 



The very same may be said regarding the starry 

 sky. You catch the light from any star in your spec- 

 troscope, it passes through the prism and gives the dia- 

 gram of Frauenhofter lines, and you can see at once that 

 this is a sun-star by force of the analysis made before- 

 hand by students of the spectroscope. 



Again you catch the ray from another star, which fur- 

 nishes you the same spectrum, but this time without 

 Frauenhoffer lines ; the spectrum is confluent and smooth. 

 What does this signify? It signifies that the star is 

 cold, i. e. a planet merely reflecting the rays of its own 

 sun. or shining in consequence of the action of ozygen 

 on the nitrogen gas of the planet's atmosphere. 



Finally this same smooth and confluent spectrum ac- 

 companied by the lines of hydrogen and azote, some- 

 times even the solar spectrum accompanied by the ap- 

 pearance of the same lines, separately , present us 

 with the picture of planetary cloud, in the former case 

 representing an already extinct solar system, in the latter 

 such a system on the road to extinction, as we shall see 

 when we come to the investigation of cloud-spots in 

 particular. 



Such unerring and invariable accuracy in the phen- 

 mena of light and the celestial forces of nature surely 



