THE SOLAR CONSTANT.—In No. 4, vol. xxxix., of the Memorie della Societa degli Spcttroscopisti Italiani Dr. Gorczynski discusses the pyrheliometric observations of the solar constant made at Ursynova (Polonia) during 1909. The value obtained was 2·05 gr. cal./cm.2 min., and, from a discussion of the values obtained at various observatories by different methods, Dr. Gorczynski concludes that this value is very near the truth.