PROCEEDINGS OF THE REGENTS. 133 



Since 1912 the Astrophysical Observatory has confirmed the vari- 

 ability of the sun by several independent methods and has perfected 

 and improved the means of determining it in several ways. A 

 notable improvement was made this year at the time when Dr. 

 Charles G. Abbot, the director, was visiting the Smithsonian Ob- 

 servatory at Calama, Chile, which is maintained under the Hodgkins 

 fund. He found that by taking into account the brightness of the 

 sky around the sun the transparency of the atmosphere for solar 

 rays could be inferred so accurately by means of measurements 

 extending over about only 10 minutes that the determination of the 

 solar heat could be made as accurately as by the older fundamental 

 process of Langley, which requires several hours of observing. The 

 computations by the new method are also much abbreviated, so that 

 now it is possible to determine the intensity of the solar radiation 

 for the given day within 2 or 3 hours instead of by methods which, 

 as heretofore, required the equivalent of 15 hours of work for one 

 observer. The new method of observing is being steadily applied 

 at the Smithsonian Observatory at Calama, Chile, and the founda- 

 tion for its application at Mount Wilson, in California, has been 

 laid. 



Studies are being made by officials of Argentina and Brazil on the 

 dependence of the temperature and rainfall of those countries on 

 the variations of the sun as reported to them by the observing sta- 

 tion at Calama. The Smithsonian Institution has now in press a 

 report by Mr. H. H. Clayton, principal forecaster of the meteoro- 

 logical service of Argentina, in which he gives investigations tending 

 to show that all the outstanding departures from normal which con- 

 stitute the weather as contrasted with the climate of a place depend 

 on variations of the sun. Without as yet fully accepting this star- 

 tling conclusion at least the importance of the observations of the 

 solar variability are greatly enhanced by these studies of Mr. Clay- 

 ton. Accordingly investigations are being made to determine the 

 best site for a proposed observatory for measuring solar variation 

 in the most cloudless region of the United States. This appears to 

 be a little north of Yuma, Calif. Plans are also being considered for 

 establishing such an observatory in Egypt, which is the most cloud- 

 less region of the world. As in every research, the drawback is the 

 lack of funds. It is greatly to be hoped that in some way means may 

 be found for establishing two or three of the special observatories 

 required for measuring the variation of the sun in the most cloudless 

 region of the earth. It is only in this way that a satisfactory basis 

 can be laid for further progress in world-wide weather forecasting 

 depending upon these measurements. 



In regard to the dependence of the weather on the terrestrial radia- 

 tion outward to space and the effect of the atmosphere upon that, re- 



