The Bright Clouds and the Aurora

Abstract

ON the morning of the 11th inst. I had an opportunity of watching the curious cirrus-like clouds as daylight came on. The display was striking, though not such a bright one as on several former occasions. It first appeared about 2.30 a.m., when there were very faint indications of the clouds; it was some minutes before I noticed that they were the same brilliant kind as has appeared so often this summer. Their apparent upper border being irregular, it was uncertain whether they in any part reached the limit to which the sun could shine upon them, or whether the apparent border was altogether the actual edge of the cloud-sheet; however, it rose higher as the sun approached the horizon, but this might be owing to the circumstance that the motion of the clouds was, as usual, from an easterly direction. At 3.33½ a.m. they were visible as far as α Andromedæ, though they were very faint west of γ. By 3.45½ a.m. they reached down to within 5° of α Aquilæ, and were rather plain there, and by this time the sheet covered most of the sky, though none of it remained visible very low down in the east. It was no longer bright in any part. At 3.55½ they reached down to within 4° of α Aquilæ, and were plainest about there, but growing fainter. I was still uncertain whether the sheet extended beyond the western apparent border, that being simply the limit of sunshine, or whether the sheet ended there; but probably the former was now the case. At 4 a.m. they were scarcely noticeable, and by 4.11 they had disappeared altogether. By this time a faint pink glow had appeared in the east.