Optical Phenomena

Abstract

IN travelling up from Leeds on Monday afternoon I was able to watch the whole progress of the remarkable sunset sky on that afternoon. The sun went down quite clear, and the sky was all but cloudless. Shortly after sunset a crimson arch appeared stretching from south-east to north-east, with a very clear greenish blue sky beneath it in the east. This crimson arch gradually proceeded westwards over the sky, and at about 4.20 was stretching from south-west to north-west. At this time it developed a number of well-defined, pointed rays or streamers radiating from the point where the sun was below the horizon. Between the arch and the western horizon was a sky of a bright silver-white colour, which was so brilliant that it gave us quite a second daylight. The crimson arch continued to sink towards the western horizon, the streamers still retaining the same relative positions. At about 4.40 it formed simply a bright crimson band along the western horizon, and the streamers still pointing out from it gave the appearance of some large forest on fire in the west. Finally, at 4.50, when we were some twelve miles north-west of Nottingham the crimson arch had entirely vanished below the horizon. At one time, when the arch was at its brightest, with the silver-white sky beneath it, it had exactly the appearance of the aurora, except that the streamers remained fixed in relative position. In the silver-white sky there seemed to be a very thin cloud layer.