f the comparatively non-luminous interior.

As the ability of the sun to warm and light this earth arises from the
peculiar properties of the thin glowing shell which surrounds it, a
problem of the greatest interest is presented in an inquiry as to the
material composition of this particular layer of solar substance.
We want, in fact, to ascertain what that special stuff can be which
enables the sun to be so useful to us dwellers on the earth. This
great problem has been solved, and the result is extremely interesting
and instructive; it has been discovered that the material which
confers on the sun its beneficent power is also a material which
is found in the greatest abundance on the earth, where it fulfils
purposes of the very highest importance. Let us see, in the first
place, what is the most patent fact with regard to the structure
of this solar mantle possessed of a glory so indescribable. It is
perfectly plain that it is not composed of any continuous solid
material. It has a granular character which is sometimes perceptible
when viewed through a powerful telescope, but which can be seen more
frequently and studied more satisfactorily on a photographic plate.
These granules have an obvious resemblance to clouds; and clouds,
indeed, we may call them. There is, however, a very wide difference
between the solar clouds and those clouds which float in our own
atmosphere. The clouds which we know so well are, of course, merely
vast collections of globules of water suspended in the air. No doubt
the mighty solar clouds do also consist of incalculable myriads
of globules of some particular substance floating in the solar
atmosphere. The material of which these solar clouds are composed
is, however, I need hardly say, not water, nor is it anything in
the remotest degree resembling water. Some years ago any attempt to
ascertain the particular substance out of which the solar clouds were
formed would at once have been regarded as futile; inasmuch as such a
problem would then have been thought to lie outside the possibilities
of human knowledge. The advance of discovery has, however, shed a
flood of light on the subject, and has revealed the nature of that
material to whose presence we are indebted for the solar beneficence.
The detection of the particular element to which all living creatures
are so much indebted is due to that distinguished physicist, Dr. G.
Johnstone Stoney.

In the whole range of science, one of the m