Young Folks' Library: Wonders of Earth, Sea and Sky HTML version

Halos—parhelia—the Spectre Of The Brocken, Etc
(From The Atmosphere.)
Treatises on meteorology have not, up to the present day, classified with sufficient
regularity the divers optical phenomena of the air. Some of these phenomena have,
however, been seen but rarely, and have not been sufficiently studied to admit of their
classification. We have examined the common phenomenon of the rainbow and we have
seen that it is due to the refraction and reflection of light on drops of water, and that it is
seen upon the opposite side of the sky to the sun in day-time, or the moon at night. We
are now about to consider an order of phenomena which are of rarer occurrence, but
which have this property in common with the rainbow, viz., that they take place also
upon the side of the sky opposite to the sun. These different optical effects are [pg 269] classed
together under the name of anthelia (from Greek, opposite to, and Greek, the sun). The
optical phenomena which occur on the same side as, or around the sun, such as halos,
parhelia, etc., will be dealt with later on.
Before coming to the anthelia, properly so called, or to the colored rings which appear
around a shadow, it is as well first to note the effects produced on the clouds and mists
that are facing the sun when it rises or sets.
Upon high mountains, the shadow of the mountain is often seen thrown either upon the
surface of the lower mists or upon the neighboring mountains, and projected opposite to
the sun almost horizontally. I once saw the shadow of the Righi very distinctly traced
upon Mount Pilate, which is situated to the west of the Righi, on the other side of the
Lake of Lucerne. This phenomenon occurs a few minutes after sunrise, and the triangular
form of Righi is delineated in a shape very easy to recognize.
The shadow of Mont Blanc is discerned more easily at sunset. MM. Bravais and Martins,
in one of their scientific ascents, noticed it under specially favorable circumstances, the
shadow being thrown upon the snow-covered mountains, and gradually rising in the
atmosphere until it reached a height of 1°, still remaining quite visible. The air above the
cone of the shadow was tinted with that rosy purple which is seen, in a fine sunset,
coloring the lofty peaks. "Imagine," says Bravais, "the other mountains also projecting, at
the same moment, their shadows into the atmosphere, the lower parts dark and slightly
greenish, and above each of these shadows the rosy surface, with the deeper rose [pg 270] of the
belt which separates it from them; add to this the regular contour of the cones of the
shadow, principally at the upper edge, and lastly, the laws of perspective causing all these
lines to converge the one to the other toward the very summit of the shadow of Mont
Blanc; that is to say, to the point of the sky where the shadows of our own selves were;
and even then one will have but a faint idea of the richness of the meteorological
phenomenon displayed before our eyes for a few instants. It seemed as though an
invisible being was seated upon a throne surrounded by fire, and that angels with
glittering wings were kneeling before him in adoration."
Among the natural phenomena which now attract our attention, but fail to excite our
surprise, there are some which possess the characteristics of a supernatural intervention.
The names which they have received still bear witness to the terror which they once