Abstract :
Discovery of reasons for the well-known beneficial effects of sunlight on health has been a stimulus to efforts to produce artificial sunshine for use when and where natural sunshine is not available. Knowledge of the amounts of energy in various wavelengths of the solar spectrum throughout the year is necessary for production of the best artificial sunlight. Therefore measurements of sunlight in summer, fall, and winter, have been made at two sanatoria, in Ohio and Colorado, where sunlight has been used for years in treating disease. The physicians in charge in Colorado have found that noon winter sunshine has given the best results.
