1 32 *The Constitution of the Sun . [March, 
Now what kind of spectrum would such a constitution 
give ? It would very probably give the solar spectrum line 
for line and band for band, but it would give the same 
spectrum over all its parts. This as a matter of fad is not 
the case, as we find the umbra of a spot to vary from its 
penumbra, faculse to be distinguishable from the adjoining 
surface, and the sun’s atmosphere itself to give an ever- 
varying speCdrum. If to fit this changing speCdra we 
assume the sun to consist of a solid body surrounded by 
glowing vapours , we will, at the same time, require to endow 
solar elements with properties differing widely from our own. 
In fad we at once require to resign the only certain ground 
that we have to work upon, and return to the doubts and 
difficulties of a bygone age. 
Everywhere throughout Nature we find simplicity and 
uniformity, — a solid changing to a liquid, and a liquid to a 
gas. But nowhere do we find gaseous iron, calcium, or 
magnesium suspended over solid sodium, nickel, or zinc. 
As long as our predecessors tried to explain planetary motion 
by their intricate cycles and epicycles, so long did they fail ; 
but the moment they applied the laws governing the motion 
of terrestrial matter all became simple, and their hitherto 
erratic hosts were seen to obey the same laws as the matter 
strewn around them. We know that the attraction which 
binds sun, planet, and system together is everywhere the 
same, whether it be engaged in building up the atoms of a 
chemical compound or holding together the constituents of 
a universe. Are we to accept this as an infallible law, not 
only when applied to force, but when compared with matter, 
the progenitor of force, and to hold that wherever matter is 
found there will we find it endowed with the same properties 
as terrestrial matter ? If we do this, and accept of the 
coincidence of the Frauenhofer lines as a sure index that the 
sun is made up of elements exactly the same as our own, 
then we require to find a new explanation for the phenomena 
taking place at the surface of the sun. 
As already mentioned, the sun, when seen through a pow- 
erful telescope, is no longer the bright unblemished mirror 
which our forefathers had pictured in their minds, but is 
seen to be a coarse-grained unpretentious-looking body, with 
its full complement of corrugations, pores, and granules, 
and its bright faculse as it were to light the way to the deep 
profundities of its vast willow-leaf strewn caverns. 
What do we know about these cavities ? Are they really 
vast cavernous depths reaching far below the surface-clouds 
hanging in a transparent atmosphere, — scoriae floating on a 
