IN CONNEXION AVITII THE SPECTRUM OF THE SUN. 
647 
clearly transparent and fusible to the end, and evolves chlorine when treated for that 
purpose. 
Strontic Fluoride was the most stable of all ; it would not fuse, gave no coloration to 
the flame, and obstinately retained its fluorine to the last, as was shown by the mass 
giving the usual reaction of fluorine when treated on a glass plate with sulphuric acid. 
Conclusion. 
These facts justify us in coming to the conclusion that the similarity of the spectra 
observed under the conditions in question is due to the fact that the spectrum observed 
is that of the oxide ; for whereas in the first instance there is a differentiation between 
the various spectra, after the action of the flame has been continued for some little time 
the spectra observed are the same. 
Considerations which follow from the above observations in connexion with the spectra of 
chemical compounds. 
General discussion of Spectra. 
In what has been said before, both in this communication and in my former paper 
on the spectra of chemical compounds, I have only referred to the lines of the metals. 
I now propose to discuss the spectra generally. 
Some of the earliest observations of this nature (1860) have been described by 
Kirchhoff and Bunsen*. They remark, “We have compared the spectra represented 
on the Plate f, which we have obtained from the pure chlorides, with those produced 
when the bromides, iodides, hydrated oxides, sulphates, and carbonates of the several 
metals are brought into the following flames 
“ Into the flame of sulphur. 
,, „ bisulphide of carbon. 
,, „ aqueous alcohol. 
Into the n on-luminous flame of coal-gas. 
Into the flame of carbonic oxide. 
„ „ hydrogen. 
Into the oxy hydrogen flame. 
“ As the result of these somewhat lengthy experiments, the details of which we here 
omit, it appears that the alteration of the bodies with which the metals employed were 
combined, the variety in the nature of the chemical processes occurring in the several 
flames, and the wide differences of temperature which these flames exhibit, produce no 
effect upon the position of the bright lines in the spectrum which are characteristic of 
each meted. 
“ It was found that the same metallic compound, placed in one of these flames, gives 
* Translated in Philosophical Magazine, 1860, vol. xx. pp. 91-93. 
t The spectra shown on the Plate are those known as llame-spectra, 
MDCCCLXXIII. 4 S 
