in the way the air of our own planet does in great storms, it
is not easy to believe that it is a fluid, yet its sharply defined
upper surface leads us to suppose that it can not well be a mere mass
of vapour. The spectroscope shows us that this chromosphere contains
in the state of vapour a number of metallic substances, such as iron
and magnesium. To an observer who could behold this envelope of the
sun from the distance at which we see the moon, the spectacle would be
more magnificent than the imagination, guided by the sight of all the
relatively trifling fractures of our earth, can possibly conceive.
From the surface of the fiery sea vast uprushes of heated matter rise
to the height of two or three hundred thousand miles, and then fall
back upon its surface. These jets of heated matter have the aspect of
flames, but they would not be such in fact, for the materials are not
burning, but merely kept at a high temperature by the heat of the
great sphere beneath. They spring up with such energy that they at
times move with a speed of one hundred and fifty miles a second, or at
a rate which is attained by no other matter in the visible universe,
except that strange, wandering star known to astronomers as
"Grombridge, 1830," which is traversing the firmament with a speed of
not less than two hundred miles a second.

Below the chromosphere is the photosphere, the lower envelope of the
sun, if it be not indeed the body of the sphere itself; from this
comes the light and heat of the mass. This, too, can not well be a
firm-set mass, for the reason that the spots appear to form in and
move over it. It may be regarded as an extremely dense mass of gas, so
weighed down by the vast attraction of the great sphere below it that
it is in effect a fluid. The near-at-hand observer would doubtless
find this photosphere, as it appears in the telescope, to be sharply
separated from the thinner and more vaporous envelopes--the
chromosphere and the corona--which are, indeed, so thin that they are
invisible even with the telescope, except when the full blaze of the
sun is cut off in a total eclipse. The fact that the photosphere,
except when broken by the so-called spots, lies like a great smooth
sea, with no parts which lie above the general line, shows that it has
a very different structure from the envelope which lies upon it. If
they were both vaporous, there would be a gradation between them.

On the surface of the photosphere, almo