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XVIII. Researches in Spectrum- Analysis in connexion with the Spectrum of the Sun . — 
No. II. By J. Norman Lockyer, F.R.S. 
Received March 14, — Read May 8, 1873. 
Contents. 
Introduction. 
I. Chemical compounds. 
«. Conditions of the experiments. 
f3. Results of experiments. 
Lead. 
Barium. 
Strontium and Magnesium. 
Sodium. 
Lithium. 
y. On the difference between flame-spectra and 
those produced by a weak electric discharge. 
Barium. 
Strontium. 
Conclusions. 
S. Experiments to determine the cause of the 
similarity of the spectra of the various salts 
observed in air. 
Conditions of the experiments. 
Spectra of Strontium salts. 
Conclusion. 
e. Considerations which follow from the above 
observations in connexion with the spectra 
of chemical compounds. 
General discussion of spectra. 
Bearing of the new observations. 
General statement. 
Spectra of the metalloids. 
Applications of these considerations to solar 
and stellar spectra. 
II. Mechanical mixtures. 
Method employed in preparing mixtures. 
Observations. 
Application of these observations to the solar 
spectrum. 
In my former communication under the above title I pointed out that the new method 
of spectroscopic research adopted by Dr. Frankland and myself had enabled me to 
establish : — 
(1) That when a metallic vapour is subjected to admixture with another gas or vapour, 
or to reduced pressure, its spectrum becomes simplified by the abstraction of the shortest 
lines and by the thinning of many lines. 
(2) That when metals are chemically combined with another element (I used 
chlorine) only the longest lines of the metal remain in the spectrum of the chloride — 
the number being large in the case of elements of low atomic weight, and small in the 
case of elements of high atomic weight and of twice the atom-fixing power of hydrogen. 
(3) That I had reason to believe that by means of mechanical admixtures the 
^ spectrum of a metal could be made simple in the same manner, thereby giving a 
foreshadowing of a quantitative spectrum-analysis. 
I then showed the bearing of these determinations on several questions connected with 
Solar Physics. 
I have now the honour of communicating to the Royal Society the results of the 
continuation of my inquiries. 
mdccclxxiii. 4 R 
