47 



metallic substances. It will be remembered, however, that 

 some of the coloured lines produced by these metallic vapours, 

 although very characteristic and decided, are but of short 

 duration. 



1st. Sodium. — The spectrum-reaction of Sodm?n produces 

 only one yellow line which is coincident with Fraunhofer's 

 dark solar line D, for if the soda and the sola?' spectra 

 were to fall one over the other the yellow soda line would 

 exactly cover the dark solar line D. This is important, as it 

 enables us to draw the conclusion respecting the presence of 

 soda in the Sun's atmosphere. 



2nd. Lithium. — The spectrum produced by this metal is 

 very beautiful and quite characteristic. It consists of one 

 intensely brilliant crimson line, and one less distinct orange 

 line. 



3rd. Chlorate of Potassium. — All compounds of this sub- 

 stance give a widely extended continuous spectrum, which 

 contains only two characteristic lines, one in the outermost 

 red, approaching the ultra-red rays, which coincides with the 

 dark line A. of the Solar Spectrum, and a second line situated 

 at the extreme end of the violet rays. 



4th. Nitrate of Strontia. — The spectrum produced by 

 Strontia is especially characterized by the absence of green 

 bands. There are eight lines in this spectrum which 

 are remarkable, namely, six red, one orange, and one blue. 

 These Strontia bands are important both as regards their 

 position and intensity. 



5th. Chloride of Barium. — The spectrum of the com- 

 pounds of Barium is the most complicated of the spectra of 

 the alkalis. It is at once distinguished from all the others by 

 two green lines, which are by far the most distinct, appearing 

 the lirst, and continuing during the whole of the reaction. 



6th. Chloride of Calcium. — This substance becomes gas at 

 the t^emperature of flame, and gives a characteristic spectrum, 

 which is distinguished from the foregoing spectra by a very 

 bright green line and one intensely bright orange line, lying 

 very near the red end of the spectrum. 



There are other substances I propose to submit if time 

 allows, viz., the metal Thalium, which j)roduces the beautiful 

 intense green Thalium line, very near the solar line D ; 

 SuljDhur, which is various ; and a mixture of the foregoing 

 substances, which gives the characteristic lines of each in the 

 spectrum. 



In conclusion, it may be asked what new knowledge have 

 we gained by prismatic analysis ? We have seen that the 

 Stars contain material elements and have a structure analagous 

 to that of the Sun, also that their colours originate in the 



