3^ 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. Jl 



Taking important individual cities and averaging the rainfalls per day 

 succeeding the day of changes in solar radiation, the following results were 

 obtained for the three summer months, December, January, and February : 



The values in the first column show how much higher the solar values were 

 on any selected day than on the preceding day, and the remaining columns 

 show the average daily rainfalls following from three to five days later. 

 These averages were derived from the monthly reports from the cities named. 



After very marked rises of solar radiations 0.050 to 0.070, there was some 

 rainfall at certain places probably because a very marked rise usually followed 

 on the succeeding day by a marked fall. After more moderate rises of from 

 0.030 to 0.050, there was practically no rain. After decreases of solar radiation 

 rainfall was general and at the northern stations increased in intensity with 

 increasing intensity of the solar changes. 



In the winter half year relation to the solar changes is a different one. 



At that time the sun is vertical over the land surfaces of the northern hemis- 

 phere where the pressure generally falls with increasing solar radiation and the 

 air overflow's to the southern continents. At any rate increases of solar 

 intensity between April and October are followed three to five days later by 

 rises of pressure and cooler weather in Argentina. 



There are certain periodic changes accompanying these solar changes which 

 are now the subject of much study in this office. These studies, it is believed, 

 will permit the prediction of the weather with a fair degree of accuracy for 

 much longer intervals in advance than three days and may perhaps extend 

 them to weeks or years. 



The solar data as now received is of aid in day to day forecasting, but it will 

 be seen from the curves that even in the dry climate of northern Chile, where 

 the solar observations are now made, there are very frequent breaks in the 

 observations due to the unfavorable state of the atmosphere, and if these 

 observations are to fulfill the great promise of usefulness which the past 

 summer's experience leads me to look forward to with confidence, then we 

 must have complete records. 



These, in my opinion, can be obtained only by the establishment of more than 

 one solar observatory devoted to this class of work. It would be a matter of 

 congratulation if Argentina could establish at least one such observatory and 

 if others could be established elsewhere, between which reports might be 

 exchanged. 



