Changes in the Solar Constant of Radiation

(1) Pettit, E. “Ultra-violet Solar Radiation.” Mount Wilson Contr., N ~ . 98. prp,.. Nat. Acad. sc., 13, 380-387, 1927. (2) Pettit, h. Measurements of Ultra-Violet Solar Radiation.” Mount Wilson Contr., No. 445; Astrophysical Jour., 75, 185-221, 1932. (3) .Davis, G. E. “Instruments for Radiometric and Radiobiological Investigations a t the Desert Sanatorium and Institute of Research, Tucson, Arizona.” Gen. Elec. Rev., 34,98-103,1931. loweratmosphere usually is accompanied by somewhat lowered radiation values. In the practice of heliotherapy. it is important to recognize the probability of frequent intensity variations of considerable magnitude. Only a very rough prediction of radiation values on any given day can be made by reference to average previously found. Accurate dosage can be determined only from