Page:Popular Science Monthly Volume 82.djvu/279

Rh In a publication which, I regret to say, bears the official imprimatur of the Weather Bureau, I find a definition of the "solar aureole, corona, or glory." These names are stated to belong to the familiar phenomenon of diffraction rings around the sun; and the question arises—Why three names for one thing? Etymologically one is as good as another; but the single term "corona" was long ago appropriated to the phenomenon in question. If we consult Pertner's "Meteorologische Optik," we shall find that, according to this authority at least, the aureole is not identical with the corona. A separate name was desired for that inner portion of the complete corona which is, as a rule, the only part visible; extending from the blue-white zone around the luminary to the reddish brown circle adjacent, but not including either indigo or violet. Pernter was, I believe, the first person to distinguish this part of the corona under the name "aureole." The glory, again, is something quite different. This is not seen around a heavenly body, but surrounds the shadow of the observer's head—strictly speaking, of the observer's eye—cast upon a cloud or fog-bank. In the phenomenon of the Brocken specter the glory constitutes the "Brocken bow"—though the specter and the bow are persistently confused in the dictionaries and in the literature of meteorology.

This leads us to a further hopelessly confused statement in connection with the definition above quoted, reading as follows: "A smaller circle surrounding the shadow of the observer's head is called an anthelion, aureole, glory, or fog shadow." The word "anthelion has, indeed, been used persistently in this sense in English literature; though such a use has never been countenanced in French or German. Bravais and his successors applied the name "anthelion" to what is sometimes called in English the "countersun"; viz., a white image of the sun seen at the same altitude as that luminary, but opposite it in azimuth—one of the rarer phenomena of the great halo family. Although this, the preferable, use of the name is absolutely ignored in the English dictionaries—which uniformly confuse the anthelion with the glory—it is not quite unknown to English writers. I find the "anthelion," in this sense of the term (as observed in the year 1762), described and figured in the "Philosophical Transactions" (abridged), Vol. 11, p. 532. A similar use of the term occurs in Howard's "Climate of London," 2d ed. (1833), Vol. 1, p. 222. As to "aureole," we have already seen how Pernter has desynonymized this term. "Fog shadow" is obviously a most inappropriate name for a ring of light. In short, the sentence above quoted, revised in accordance with the requirements of accurate terminology, would read: "A smaller circle surrounding the shadow of the observer's head is called a glory." The three other names are untenable.