]

"Flames" or "prominences," if more conspicuous, are less constant in
their presence than the glowing stratum from which they spring. The
first to describe them was a Swedish professor named Vassenius, who
observed a total eclipse at Gothenburg, May 2 (o.s.), 1733.[181] His
astonishment equalled his admiration when he perceived, just outside the
edge of the lunar disc, and suspended, as it seemed, in the coronal
atmosphere, three or four reddish spots or clouds, one of which was so
large as to be detected with the naked eye. As to their nature, he did
not even offer a speculation, further than by tacitly referring them to
the moon. The observation was repeated in 1778 by a Spanish Admiral, but
with no better success in directing efficacious attention to the
phenomenon. Don Antonio Ulloa was on board his ship the _Espagne_ in
passage from the Azores to Cape St. Vincent on the 24th of June in that
year, when a total eclipse of the sun occurred, of which he has left a
valuable description. His notices of the corona are full of interest;
but what just now concerns us is the appearance of "a red luminous
point" "near the edge of the moon," which gradually increased in size as
the moon moved away from it, and was visible during about a minute and a
quarter.[182] He was satisfied that it belonged to the sun because of
its fiery colour and growth in magnitude, and supposed that it was
occasioned by some crevice or inequality in the moon's limb, through
which the solar light penetrated.

Allusions less precise, both prior and subsequent, which it is now easy
to refer to similar objects (such as the "slender columns of smoke" seen
by Ferrer)[183] might be detailed; but the evidence already adduced
suffices to show that the prominences viewed with such amazement in 1842
were no unprecedented or even unusual phenomenon.

It was more important, however, to decide what was their nature than
whether their appearance might have been anticipated. They were
generally, and not very incorrectly, set down as solar clouds. Arago
believed them to shine by reflected light,[184] but the Abbe Peytal
rightly considered them to be self-luminous. Writing in a Montpellier
paper of July 16, 1842, he declared that we had now become assured of
the existence of a third or outer solar envelope, composed of a glowing
substance of a bright rose tint, forming mountains of prodigious
elevation, analogous in character to the clouds piled above our
horizo