Colour of the Sky

Abstract

Your correspondent “H. A. N.” will find some interesting remarks on the blueness of the sky in Professor Tyndall's “Glaciers of the Alps” (p. 257, &c.), and one or two additional notes in my “Alpine Regions,” p. 150. With regard to the colour of the sky at great heights, I can inform him that in fine weather the blue becomes deeper as one ascends, as has been noticed by many persons accustomed to mountain climbing. The most striking instance that I have seen was during an ascent of Monte Rosa, 15,217 feet. On this occasion the colour was so deep as almost to approach a black, as deep as or deeper than the richest hues of Gentiana acaulis. This intensity of colour was only very conspicuous during the last few hundred feet of the ascent; and in expeditions to mountains of nearly the same height I have not often seen it approached, never surpassed. Mr. Hincliff in his “Summer Months among the Alps,” p. III, calls attention to the same phenomenon on Monte Rosa, and very appositely quotes Shelley : The sun's unclouded orb Rolled through the black concave.