though it would stand much
more heat than a wire of iron or of steel, would not have retained the
solid form by the time it had been raised to the temperature necessary
for an incandescent lamp.

There is no known metal, and perhaps no substance whatever, which
demands so high a temperature to fuse it as does the element carbon.
A filament of carbon, and a filament of carbon alone, will remain
unfused and unbroken when heated by the electric current to the
dazzling brilliance necessary for effective illumination. This is
the reason why this particular element is so indispensable for our
incandescent electric lamps. Modern research has now taught us that,
just as the electrician has to employ carbon as the immediate agent in
producing the brightest of artificial lights down here, so the sun in
heaven uses precisely the same element as the immediate agent in
the production of its transcendent light and heat. Owing to the
extraordinary fervor which prevails in the interior parts of the sun,
all substances there present, no matter how difficult we may find
their fusion, would have to submit to be melted, nay, even to be
driven off into vapor. If submitted to the heat of this appalling
solar furnace, an iron poker, for instance, would vanish into
invisible vapor. In the presence of the intense heat of the inner
parts of the sun, even carbon itself is unable to remain solid.
It would seem that it must assume a gaseous form under such
circumstances, just as the copper and the iron and all the other
substances do which yield more readily than it to the fierce heat of
their surroundings.

The buoyancy of carbon vapor is one of its most remarkable
characteristics. Accordingly immense volumes of the carbon steam
in the sun soar at a higher level than do the vapors of the other
elements. Thus carbon becomes a very large and important constituent
of the more elevated regions of the solar atmosphere. We can
understand what happens to these carbon vapors by the analogous case
of the familiar clouds in our own skies. It is true, no doubt, that
our terrestrial clouds are composed of a material totally different
from that which constitutes the solar clouds. The sun evaporates the
water from the great oceans which cover so large a proportion of our
earth. The vapor thus produced ascends in the form of invisible gas
through our atmosphere, until it reaches an altitude thousands of
feet above the surface of the earth. The chill that the