The transparency of amorphous silica for ultra-violet radiations

✍ Scribed by G.F.S.

• Publisher: Elsevier Science
• Year: 1927
• Tongue: English
• Weight: 66 KB
• Volume: 204
• Category: Article
• ISSN: 0016-0032
• DOI: 10.1016/s0016-0032(27)91701-3

✦ Synopsis

694

CURRENT TOPICS.

[J. F. I.

high over the earth and in the west toward, the sun, was in the sunshine. This was verified by calculation. Subsequent comparison of other unusually high auroras showed that they also had been exposed to sunlight. Rays with their lower edges 300 to 40o kin. above the earth and their highest points at an elevation of 600 or 800 kin. were illuminated by the sun throughout, 95 to IOO per cent. of the ordinary rays seen at Oslo from 191I to 1922 were in darkness and had no higher range than from IOO to 4o0 kin. The high auroras have generally red, blue or violet as colors, while the lower ones are a greenish-yellow. The spectroscopic study of the high auroras may furnish very valuable data on their origin and on the conditions holding in the upper atmosphere. G.F.S.