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 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 deg., 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 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.”