The Fog Bow

Abstract

THE complete theory of the rainbow, as developed by Sir George Airy (Camb. Phil. Trans., vi. p. 379, 1836), besides explaining the supernumerary bows, shows that the main bow has a radius somewhat smaller than that calculated on the ordinary geometrical theory. The smaller the drops the greater is the discrepancy. With the tiny drops composing a fog, the discrepancy is so marked that the bow receives a new name—the fog-bow, or “arc-en-ciel blanc.” Mr. Mohn's (NATURE, February 23, p. 391) nearly simultaneous measurements of the fog-bow and Ulloa's rings afford a capital opportunity of putting the theory to the test, for from the latter phenomenon we can readily calculate the average size of the particles.