[March, 
130 The Constitution of the Sun . 
With the exception of some minor details, the foregoing 
are nearly all the facts that have been gleaned with the aid 
of the telescope alone ; but when combined with the spec- 
troscope there is still a vast field to explore. 
As it is beyond the scope of this paper to go into the 
details of spectrum analysis, I will take it for granted that 
the reader is already familiar with the subject, and merely 
state a few general principles bearing on solar pheno- 
mena. 
Sunlight, as seen through a spectroscope, presents the 
appearance of a rainbow-tinted band, interspersed with nu- 
merous black lines which have been termed, from the name 
of their discoverer, Frauenhofer lines. These lines invari- 
ably occupy the same place in the solar spectrum, main- 
taining their respedbive distances one from another, whether 
the light be received diredb from the sun or refledbed from 
the moon, planets, or other opaque bodies. 
An incandescent solid or liquid, when looked at through 
a spedtroscope, gives a continuous spedbrum free from black 
lines ; but if the solid or liquid body be heated until it is in 
the state of a glowing vapour, the continuous spedbrum will 
disappear, and be replaced by a series of bright lines , each 
vapour having its characteristic lines as to colour and posi- 
tion, so that we can at once infer to which particular element 
the spedbrum belongs. 
An incandescent body shining through a vapour gives a 
continuous spedbrum, interspersed with black lines corre- 
sponding to the bright lines which the vapour would have 
given alone. 
The spedbrum of light refledbed from an opaque body de- 
pends on the nature of the medium surrounding the reflector. 
If the light has to pass through a vapour before reaching 
the opaque body, the black lines corresponding to the vapour 
will be intensified, and if the reflector is self-luminous the 
spectrum belonging to it will be superadded to that of the 
refledbed light. 
The spectrum of any element may vary according to the 
conditions of temperature and pressure under which it gives 
out its light. 
With these facts for our guidance we may now proceed 
to the actual examination, the first question which presents 
itself being — Is the body of the sun composed of the same 
elements as our earth, and, if so, are these bodies for the 
most part in a solid, liquid, or gaseous condition ? 
When the spectra of a number of different terrestrial ele- 
ments are compared with the solar spectrum, it is found that 
