The Red Glows

Abstract

I HAVE recently been staying at Zermatt and have observed the great corona or circle round the sun mentioned by your correspondent, Mr. T. W. Backhouse, in NATURE for August 14 (p. 359). It was very distinct on July 29, both at Zermatt and on the Garnergrat, and likewise on the four following days. On August 3 rain fell in the evening, but the night became cloudless; on the 4th the corona had gone. I noted the following points:—(1) The colour of the circle was like the red of clean copper when it has become coated with suboxide; this faded away into what appeared brown against the blue sky. (2) Immediately surrounding the sun and between it and the circle the sky was blue. (3) The spectroscope directed towards the blue sky or a white cloud showed a complete absence of the bands lying near B, C, and D, which indicate the presence of water vapour. (4) A band appearing like a broad line was observed between D and E, distinct, but of lesser density than it usually appears at lower elevations. (5) There did not appear to be any marked difference in the intensity of the colour of the corona when viewed on the same day at altitudes varying between 6000 and 10,000 feet. (6) After rain had fallen on the evening of August 3 the almost cloudless sky altered in appearance; in that part close to the sun it appeared whitish, and the whiteness diminished as the distance from the sun increased, until it had faded away into blue. (7) On occasions when there were fleecy clouds in the sky during the visibility of the corona, the clouds as they approached the corona appeared of a pale but very vivid green. This colour effect was due to contrast.