Page:Popular Science Monthly Volume 28.djvu/481

Rh record of parhelia for twenty-five years, confirms this opinion. We may, therefore, safely accept the conclusion that the change of color from the blue of the open sky to the intense glare of whitish light close around the sun, was until lately effected without the appearance of any reddish tinge in the transitional area.

The new corona, to which the name of "Bishop's ring" has been given after its first observer, has never been a very conspicuous affair, and therefore has not attracted the popular attention that it deserves; but it could easily be seen every clear day last winter, and has repeatedly been noticed since then in the latter months of 1885. The hazy days of summer are not favorable to its visibility. It is best seen from elevated stations, which gain their sky-colors chiefly from the finer particles floating at great altitudes, as they are above the lower strata of the atmosphere where the relatively coarse, haze-making dust is suspended. Forel, of Morges, one of the most acute observers of terrestrial physics in Switzerland, reports the distinct visibility of the ring from mountain-tops, while it is not to be seen from the valleys, where the whitish, hazy light overpowers its delicate colors. He adds that many of his countrymen in the higher Alps had been struck with the appearance of the new color in the sky before they had heard mention of it. For the same reason Tissandier found the distinctness of the corona greatly increased when viewed from a balloon high above the dusty air of Paris. At low-level stations it is best seen during the persistence of that type of weather known as "anti-cyclonic" among modern meteorologists. Such weather is characterized by high barometric pressure, and consequently has descending currents of pure, clean upper air. The sky is then brilliantly clear and free from haze, and at such times last winter the ring was of remarkable distinctness. Thin cirrus clouds generally hide it; but the presence of scattered, sharp-edged cumulus clouds adds to its visibility in the clear spaces between them. Let one of them stand before the sun, so that its heavy shadow darkens the lower air, whose reflecting particles ordinarily add much white light to the blue of the sky; then, looking between the clouds in the neighborhood of the sun, a broad arc of the ring appears with its colors blending in what may be fairly called the most delicate intensity. Just before a moderate thunder-storm early last June, the ring was thus presented with most beautiful effect. It was seen in Cambridge with extraordinary distinctness on the afternoon of November 2, 1885, when the lower clouds of a heavy rainstorm rapidly broke away in the west, about two o'clock, leaving the sun well hidden behind a sheet of upper cloud and a space of open sky below it. The lower air was thus well shaded from direct sunlight, and the strength of the colors was most remarkable. There was first the margin of the glowing central area at the edge of the cloud, soon turning pale brassy yellow, and then strong reddish gold at about fifteen to twenty degrees from the sun; farther out yet was the delicate