ABBOT: SOLAR RADIATION MEASUREMENTS 23I 



1913, 191 4, 1915 and 1916/ for the months May to November, 

 The solar observations were made at Mount Wilson. Note the 

 pronounced and opposite courses of the temperature departures 

 after high and low solar radiation values, and the nearly normal 

 temperature following mean solar values. Note, too, that the 

 temperature departures are not small. They amount to several 

 whole degrees, not mere tenths of degrees. In fact on the 

 second, tenth, and seventeenth day after the event, the tem- 

 perature departure after the high solar radiation differs in each case 

 more than 6° F. from the corresponding departure after low 

 values. This corresponds to 5 per cent change in the sun's 

 radiation. Meteorologists need not be reminded that 6° F. 

 change in the mean temperature of a whole day is not trifling. 

 People in general would also very easily recognize a day whose 

 mean temperature was 90° from one of 84° F., or one of 10° F. 

 from one of 16° F. 



Perhaps equally or more important in Argentina, where there 

 is hardly adequate rainfall, are Clayton's results on the depend- 

 ence of precipitation on solar radiation, if confirmed.^ He finds 

 that heavy rains are apt to occur from three to five days after 

 large decreases of the solar radiation. He shows this result by 

 table I. 



At times of nearly stationary solar intensities there seems to 

 be practically no precipitation in these cities of Argentina. In 

 a few instances precipitation follows large increases of radia- 

 tion. But almost universally great decreases of solar radiation 

 are followed in from 3 to 5 days by heavy precipitation. Such 

 information is of great value for vineyard growers and agricul- 

 turists in other lines if it proves to be well founded. 



These are but specially striking samples of the results which 

 Clayton lays before us. He has discussed all of the Mount 

 Wilson and Calama solar observations for their bearing on the 



^ Clayton did not have solar results of 191 6 and 191 7 available for study when 

 he obtained these results. 



° Clayton's statement is not specific at this point, but I think his precipitation 

 table depends only on a few months of observation, not on the mean of 4 years 

 like the temperature data. 



