Halos—parhelia—the Spectre Of The Brocken, Etc

Some few years ago, in the summer of 1862, a French artist, M. Stroobant, witnessed and carefully sketched this phenomenon, which is drawn in full-page illustration, opposite p. 272. He had slept at the inn of the Brocken, and rising at two in the morning, he repaired to the plateau upon the summit in the company of a guide. They reached the highest point just as the first glimmer of the rising sun enabled them to distinguish clearly objects at a great distance. To use M. Stroobant's own words, "My guide, who had for some time appeared to be walking in search of something, suddenly led me to an elevation whence I had the singular privilege of contemplating for a few instants the magnificent effect of mirage, which is termed the Spectre [pg 272] of the Brocken. The appearance is most striking. A thick mist, which seemed to emerge from the clouds like an immense curtain, suddenly rose to the west of the mountain, a rainbow was formed, then certain indistinct shapes were delineated. First, the large tower of the inn was reproduced upon a gigantic scale; after that we saw our two selves in a more vague and less exact shape, and these shadows were in each instance surrounded by the colors of the rainbow, which served as a frame to this fairy picture. Some tourists who were staying at the inn had seen the sun rise from their windows, but no one had witnessed the magnificent spectacle which had taken place on the other side of the mountain."

Sometimes these spectres are surrounded by colored concentric arcs. Since the beginning of the present century, treatises on meteorology designate, under the name of the Ulloa circle, the pale external arch which surrounds the phenomenon, and this same circle has sometimes been called the "white rainbow." But it is not formed at the same angular distance as the rainbow, and, although pale, it often envelops a series of interior colored arcs.

"THE SPECTRE OF THE BROCKEN"

Ulloa, being in company with six fellow-travellers upon the Pambamarca at daybreak one morning, observed that the summit of the mountain was entirely covered with thick clouds, and that the sun, when it rose, dissipated them, leaving only in their stead light vapors, which it was almost impossible to distinguish. Suddenly, in the opposite direction to where the sun was rising, "each of the travellers beheld, at about seventy feet from where he was standing, his own [pg 273] image reflected in the air as in a mirror. The image was in the centre of three rainbows of different colors, and surrounded at a certain distance by a fourth bow with only one color. The inside color of each bow was carnation or red, the next shade was violet, the third yellow, the fourth straw color, the last green. All these bows were perpendicular to the horizon; they moved in the direction of, and followed, the image of the person they enveloped as with a glory." The most remarkable point was that, although the seven spectators were standing in a group, each person only saw the phenomenon in regard to his own person, and was disposed to disbelieve that it was repeated in respect to his companions. The extent of the bows increased continually and in proportion to the height of the sun; at the same time their colors faded away, the spectre [pg 274] became paler and more indistinct, and finally the phenomenon disappeared altogether. At the first appearance the shape of the bows was oval, but toward the end they became quite circular. The same apparition was observed in the polar regions by Scoresby, and described by him. He states that the phenomenon appears whenever there is mist and at the same time shining sun. In the polar seas, whenever a rather thick mist rises over the ocean, an observer, placed on the mast, sees one or several circles upon the mist.

THE ULLOA CIRCLE.

These circles are concentric, and their common centre is in the straight line joining the eye of the observer to the sun, and extended from the sun toward the mist. The number of circles varies from one to five; they are particularly numerous and well colored when the sun is very brilliant and the mist thick and low. On July 23, 1821, Scoresby saw four concentric circles around his head. The colors of the first and of the second were very well defined; those of the third, only visible at intervals, were very faint, and the fourth only showed a slight greenish tint.

The meteorologist Kaemtz has often observed the same fact in the Alps. Whenever this shadow was projected upon a cloud, his head appeared surrounded by a luminous aureola.

To what action of light is this phenomenon due? Bouguer is of opinion that it must be attributed to the passage of light through icy particles. Such, also, is the opinion of De Saussure, Scoresby, and other meteorologists.

In regard to the mountains, as we cannot assure ourselves directly of the fact by entering the clouds, we [pg 275] are reduced to conjecture. The aerostat traversing the clouds completely, and passing by the very point where the apparition is seen, affords one an opportunity of ascertaining the state of the cloud. This observation I have been able to make, and so to offer an explanation of the phenomenon.

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