For more than fifteen years the Astrophysical Observatory of the Smithsonian Institution has been engaged in making measurements of the radiation of the sun. These measurements have indicated that the sun's emission is variable. The Institution now maintains two stations— one in Arizona and the other in Chile—for observing the solar variability. Telegraphic reports of the results obtained in Chile have been forwarded to Buenos Aires and Rio de Janeiro for the use of the meteorological services of Argentina and Bra