SOLAR CHEMISTRY. 
213 
line. This holds true for all the substances which have yet been 
examined. The coloured bright lines are converted into dark 
lines, if the rays from the coloured flames are made to permeate 
vapours of the same constitution as those which produced the 
particular spectrum under examination. 
Incandescent gases and vapours give off Light of certain 
definite degree of refrangibility, or they furnish spectra consist- 
ing of certain fixed lines ; and those incandescent gases or 
vapours absorb Light of the same degree of refrangibility as that 
which they emit. This is only the expression in relation to 
Light of the celebrated statement made in regard to Sound — 
that a body absorbs all the oscillations which it can propagate. 
All the bright lines of the spectra produced by the vapours of 
known metals which have yet been examined appear to be 
represented by the dark lines of the solar spectrum. Angstrom 
says, "The analogy between the two spectra, the metal and the 
solar, may be more or less complete when we consider the details. 
When taken together, they produce the impression of one being 
the reverse of the other. I am therefore convinced that the 
cause of the hues of the solar spectrum involves that of the 
bright electric lines.-” 
It is difficult, within a limited space, to express, in terms 
which shall be intelligible to those who have had no previous 
acquaintance with the subject, the evidences which support the 
views of Kirchoff as respects the Sun. If we have been suc- 
cessful in our description of the phenomena involved in the con- 
sideration of this subject, it will be understood that all the 
bright lines which are seen when we produce spectra from the 
coloured flames obtained by burning any of the metals, corre- 
spond with the black lines of the solar spectrum. That is 
to say, dark lines always existing in the solar spectral image 
correspond with every line produced by a spectrum obtained by 
burning Iron ; and so with regard to the other metals which 
have been examined. 
The conclusion, therefore, is that the radiations from the centre 
of our system, — the Sun, — producing the phenomena of Light, 
Heat, and Actinism, — are due to the combustion of metallic 
bodies such as we find on this Earth. 
The mass of the sun is, according to this hypothesis, regarded 
as being intensely incandescent. Matter, in all respects, pro- 
bably, similar to that with which we are acquainted, is under- 
going combustion, and, of course, surrounding the sun with a 
vaporiform atmosphere, consisting of the emanations from the 
ignited nucleus. But for this atmosphere (or, to employ a 
better term, this photosphere) , the solar spectrum would give 
a series of biilliantly-coloured bright bands. We have 
stated that vapours are opaque to their own class of rays : 
