tween the arch and the western horizon "a sky of a bright silver-white color, which was so brilliant that it gave us quite a second daylight"; at another, of the sky nearer the zenith appearing "of a sea-green tint." The sea-green tint in the east was observed at Rome; and at Berlin, according to Herr Robert von Helmholtz, there was "a greenish sunset at 3.50, an unusually bright-red sky with flashes of light starting from southwest. An interesting physiological phenomenon which recalls 'Contrast-Farben' was there beautifully illustrated by some clouds, no longer reached by direct sunlight; they looked intensely green on the red sky." The whole phenomenon was exhibited, according to Mr. J. Addington Symonds, with remarkable intensity at Davos-Platz in the High Alps; and on one occasion "the whole north-eastern region of the heavens was at the same time of the most vivid golden-green—the peculiar green of chrysoprase and some highly-tinted beryls. Each tone of light, rose and green, was reflected on the long, broad basin of valley snow, the blending of both colors being of a strange, bewildering brilliancy." The sun, at this place, appeared through the day "surrounded by a luminous, slightly opalescent haze—not at all resembling halo or iridescence of vapor."
The red glow and the green sun are most likely due to a common cause. The same medium which will give by transmitted light a green color to objects viewed through it, will, by the universal law of the absorption and reflection of light, reflect the red rays. The close connection of the two phenomena may be regarded as real.
The spectacle must be due to some peculiar condition of our atmosphere, for, if it was produced by any cause outside of the atmosphere, it would have been visible in some form through the night, whereas its duration corresponded tolerably closely with that of ordinary twilight; the cause must have been co-extensive with the atmosphere, for the glow lasted as long as the twilight, if not longer. The manifestation was not auroral or electrical, for no auroras have been seen which could reasonably be associated with it, and no electrical disturbances have been mentioned in connection with it, except at Madras. Professor Michie Smith, of Madras, and Professor C. Piazzi Smyth, believe that it is the result of peculiar conditions of vapor in the air; but, while this might easily account for colors lasting a few days, it is difficult to suppose a peculiar accumulation and distribution of ordinary vapors enduring for so long a period. Nevertheless, Mr. Lockyer has seen the sun green through the steam of a steamboat; it has been seen green through the mist of the Simplon; and Mr. Henry Bedford, describing the summer sunset and sunrise just within the Arctic Circle in July, 1878, in an English magazine of that year, said: "The color brightens, and some small streaks of clouds grow brighter and brighter, until the sun—the green sun—appears. A distant low range of rocks comes between us and its point of rising, and, as we glide on, an opening between them shows us the sun, a
