precise observation of these curious solar flames. That reproduced
here was observed in Rome, January 30, 1885. It measured 228,000
kilometers (141,500 miles) in height, eighteen times the diameter of the
earth (represented alongside in its relative magnitude). (Fig. 31.)

Solar eruptions have been seen to reach, in a few minutes, a height of
more than 100,000 kilometers (62,000 miles), and then to fall back in a
flaming torrent into that burning and inextinguishable ocean.

Observation, in conjunction with spectral analysis, shows these
prominences to be due to formidable explosions produced within the
actual substance of the Sun, and projecting masses of incandescent
hydrogen into space with considerable force.

Nor is this all. During an eclipse one sees around the black disk of the
Moon as it passes in front of the Sun and intercepts its light, a
brilliant and rosy aureole with long, luminous, branching feathers
streaming out, like aigrettes, which extend a very considerable distance
from the solar surface. This aureole, the nature of which is still
unknown to us, has received the name of _corona_. It is a sort of
immense atmosphere, extremely rarefied. Our superb torch, accordingly,
is a brazier of unparalleled activity--a globe of gas, agitated by
phenomenal tempests whose flaming streamers extend afar. The smallest of
these flames is so potent that it would swallow up our world at a single
breath, like the bombs shot out by Vesuvius, that fall back within the
crater.

What now is the real heat of this incandescent focus? The most accurate
researches estimate the temperature of the surface of the Sun at
7,000 deg.C. The internal temperature must be considerably higher. A
crucible of molten iron poured out upon the Sun would be as a stream of
ice and snow.

We can form some idea of this calorific force by making certain
comparisons. Thus, the heat given out appears to be equal to that which
would be emitted by a colossal globe of the same dimensions (that is, as
voluminous as twelve hundred and eighty thousand terrestrial globes),
entirely covered with a layer of incandescent coal 28 kilometers (18
miles) in depth, all burning at equal combustion. The heat emitted by
the Sun, at each second, is equal to that which would result from the
combustion of eleven quadrillions six hundred thousand milliards of tons
of coal, all burning together. This same heat would bring to the boil in
an hour, two trillions nine hu