1883.] 
The Constitution of the Sun . 
131 
the bright lines belonging to several of these elements ex- 
actly correspond with the position of certain black lines in 
the solar spedtrum. From these coincidences Kirchhoff 
concluded that those elements which gave spedtra consisting 
of bright lines corresponding with solar black lines must 
not only form part of the body of the sun, but enter into the 
composition of his atmosphere. He reasoned — “ There is 
a solid or a liquid something in the sun, giving a continuous 
spedtrum, and around this there are vapours of sodium, of 
iron, of calcium, of chromium, [of barium, of magnesium, 
of nickel, of copper, of strontium, of cobalt, and of alumi- 
nium ; all these are existing in an atmosphere, and are 
stopping out the sun’s light. If the sun were not there, and 
if these things were observed in an incandescent state, we 
should get bright lines from them.” 
“ Such, then, is Kirchhoff’s theory of the sun. There is 
a something — Kirchhoff said it was a liquid— which gives 
us a continuous spedtrum, and between our eye and that 
incandescent liquid surface there is an enormous atmosphere, 
built up of vapours of sodium, iron, and so on ; and the 
reason that we get the dark lines is that the molecules of 
the substances named absorb certain rays, those, namely, 
which they produce when they are in an incandescent 
state.” * 
Now if this inference of Kirchhoff’s, that the sun contains 
the same elements as the earth, be corredt, it follows that 
if they are the same in one respedt — namely, in that of 
emitting the same kind of light — it is almost certain that 
they are the same in every other respedt, and that the 
elements which go to form the sun obey the same chemical 
and physical laws as these elements would do at the earth’s 
surface. 
If we accept this elementary sameness as a fadt, and wish 
to explain solar phenomenon on a fiery basis, then since 
iron, calcium, and magnesium are invariably found in the 
spedtrum of the sun’s atmosphere, and since these bodies 
cannot be rendered gaseous without first passing through the 
liquid condition, we must infer that, if not the whole, at 
least the surface of the sun is in a molten state. And this 
molten mass must consist either of layers of the elements 
arranged according to their densities, or of a homogeneous 
mixture formed in accordance with the laws of liquid 
diffusion. And the gaseous envelope surrounding the sun 
must also be diffused or stratified in the same manner. 
* Lockyer’s Solar Physics. 
