SECT. iv. SPECTRA OF THE PLANETS. 161 



brighter parts of the nebula. As soon as the light from 

 one of these stars entered the slit of the instrument, its 

 continuous spectrum was seen to flash across the field of 

 vision in a long coloured band. This shows that the 

 mass of matter in this immense nebula is in a different 

 state from that of the stars themselves, as Mr. Huggins 

 had already observed. Padre Secchi does not draw any 

 inference from his observations as to the structure of 

 nebulse in general, probably thinking it premature, but 

 he expresses astonishment at their results. 



Since the preceding lines were written, Mr. Huggins 

 and Professor W. A. Miller have continued their re- 

 searches on the constitution of the celestial bodies by a 

 method of direct simultaneous comparison of the lines 

 in their spectra with the lines in the spectra of many of 

 the terrestrial elements. The spectra for comparison 

 were obtained from the spark of the induction coil 

 taken between points of various metals ; and sometimes 

 a platinum wire was used, surrounded with cotton, 

 moistened with a solution of the substance required. 

 The telescope of the instrument was mounted equato- 

 rially, and followed the star by clockwork. By this 

 arrangement the spectrum of the star, and the spectrum 

 of the metal compared with it, are seen in juxtaposition ; 

 and the coincidence or relative position of a dark line 

 in the stellar spectrum with a bright line in the metallic 

 spectrum can be determined with great precision. 



It was found that Jupiter's atmosphere has a much 

 greater absorptive power than the terrestrial atmosphere ; 

 that they have some gases or vapours in common, but 

 that they are not identical. 



Some of the lines seen in the atmosphere of Saturn 

 appear to be identical with those seen in the spectrum 

 of Jupiter. 



' The lines characterizing the atmospheres of Jupiter 

 and Saturn are not present in the spectrum of Mars. 



VOL. i. M 



