260 FRAGMENTS OF SCIENCE. 
light of our electric lamp shining through such a composite 
flame would give us a spectrum cut up by dark lines, 
exactly as the solar spectrum is cut up by the lines of 
Fraunhofer. 
Thus by the combination of the strictest reasoning with 
the most conclusive experiment, we reach the solution 
of one of the grandest of scientific problems the constitu- 
tion of the sun. The sun consists of a nucleus surrounded 
by flaming atmosphere. The light of the nucleus would 
give us a continuous spectrum, like that of our common 
carbon-points; but having to pass through the photosphere, 
as our beam had to pass through the flame, those rays of 
the nucleus which the photosphere can itself emit are 
absorbed, and shaded spaces, corresponding to the partic- 
ular rays absorbed, occur in the spectrum. Abolish the 
solar nucleus, and we should have a spectrum showing a 
bright line in the place of every dark line of Fraunhofer. 
These lines are therefore not absolutely dark, but dark by 
an amount corresponding to the difference between the 
light of the nucleus intercepted by the photosphere, and 
the light which issues from the latter. 
The man to whom we owe this noble generalization is 
Kirchhoff, professor of natural philosophy in the Uni- 
versity of Heidelberg; * but, like every other great dis- 
covery, it is compounded of various elements. Mr. Talbot 
observed the bright lines in the spectra of colored flames. 
Sixteen years ago Dr. Miller gave drawings and descriptions 
of the spectra of various colored flames. Wheatstone, 
with his accustomed iugenuity, analyzed the light of the 
electric spark, and showed that the metals between which 
the spark passed determined the bright bands in the 
spectrum of the spark. Masson published a prize essay on 
these bands; Van der Willigen, and more recently Plucker, 
have given us beautiful drawings of the spectra, obtained 
from the discharge of Ruhmkorif's coil. But none of these 
distinguished men betrayed the least knowledge of the 
connection between the bright bands of the metals and the 
dark lines of the solar spectrum. The man who came 
nearest to the philosophy of the subject was Angstrom. 
In a paper translated from PoggendorfFs Annalen by 
myself, and published in the Philosophical Magazine 
*Now professor in the University of Berlin. 
