Emission and Absorption of Rays of same Refrangibility. 195 
Professor Kirchhoff’s communication “On Fraunhofer’s Lines,” 
dated Heidelberg, 20th of October, 1859, was brought before the 
Berlin Academy on the 27th of that month, and is printed in 
the Monatsbericht, p. 662. 
“ On the occasion of an examination of the spectra of coloured 
flames not yet published, conducted by Bunsen and myself in 
common, by which it has become possible for us to recognize the 
qualitative composition of complicated mixtures from the appear- 
ance of the spectrum of their blowpipe-flame, I made some ob- 
servations which disclose an unexpected explanation of the origin 
of Fraunhofer’s lines, and authorize conclusions therefrom re- 
specting the material constitution of the atmosphere of the sun, 
and perhaps also of the brighter fixed stars. 
« Fraunhofer had remarked that in the spectrum of the flame 
of a candle there appear two bright lines, which coincide with the 
two dark lines D of the solar spectrum. The same bright lines 
are obtained of greater intensity from a flame into which some 
common salt is put. I formed a solar spectrum by projection, 
and allowed the solar rays concerned, before they fell on the slit, 
to pass through a powerful salt-flame. If the sunlight were 
sufficiently reduced, there appeared in place of the two dark 
les D two bright lines; if, on the other hand, its intensity 
surpassed a certain limit, the two dark lines D showed themselves 
in much greater distinctness than without the employment of 
the salt-flame. 
“The spectrum of the Drummond light contains, as a general 
rule, the two bright lines of sodium, if the luminous spot of the 
cylinder of lime has not long been exposed to the white heat ; 
if the cylinder remains unmoved these lines become weaker, and 
finally vanish altogether. If they have vanished, or only faintly 
appear, an alcohol flame into which salt has been put, and which 
~ is placed between the cylinder of lime and the slit, causes two dark 
lines of remarkable sharpness and fineness, which in that respect 
agree with the lines D of the solar spectrum, to show themselves in 
their stead Thus the lines D of the solar spectrum are artificially 
evoked in a spectrum in which naturally they are not present. 
“ Tf chloride of lithium is brought into the flame of Bunsen’s 
gas-lamp, the spectrum of the flame shows a very bright sharply 
defined line, which lies thidway between Fraunhofer’s lines B 
and C, If, now, solar rays of moderate intensity are allowed to 
fall through the flame on the slit, the line at the place pointed 
out is seen bright on a darker ground; but with greater strength 
of sunlight there appears in its place a dark line, which has quite 
the same character as Fraunhofer’s lines. If the flame be taken 
away, the line disappears, as far as I have been able to see, com- 
pletely. 
