Measurement of Ultra-Violet Light

Abstract

IN measuring the amount of ultra-violet light reaching the earth from sun and sky, it is customary to expose the acetone methylene blue tube in the vertical position. Since more ultra-violet light is received from the sun itself than from the whole of the rest of the sky put together, the vertical position seems unsuitable, for the amount of ultra-violet light received by the contents of the tube will be too low during the time of day and year when the sun is most nearly overhead. The horizontal position has occasionally been used, but this is open to the opposite criticism.