Glasses Transparent to Ultra-Violet Radiation

Abstract

IN his letter to NATURE of Jan. 18, Dr. English suggests that our conclusion (NATURE, Sept. 21, 1929) that “complete degeneration by a mercury arc lamp results in a greater loss of ultra-violet transparency than does natural solarisation”, is merely a confirmation of his statement (Glass, Sept. 1928) that eight hours' exposure to a mercury vapour lamp is equivalent to six months' exposure to sunshine.