54 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL.. 



In figure 41 are plotted the mean values of solar radiation asso- 

 ciated with faculae separately observed on the east and west limbs 

 of the sun, derived from observations at the Observatory of La Plata 

 in the years 1920 and 1921. The continuous line shows the mean 

 solar radiation for the interval from one day before to 14 days after 

 the appearance of faculas on the east limb of the sun, and the broken 

 curve shows the mean solar radiation for 12 days before and two days 

 after the appearance of faculse on the west limb. The plot shows 

 that there was a sharp maximum of faculae at zero day when the 



Fig. 41. — Mean values of solar radiation associated with faculae on sun's limb, 

 (i) Mean solar radiation one day before and fourteen days after appearance of 

 faculae on east limb of sun. (2) Mean solar radiation 12 days before and 2 

 days after appearance of faculae on west limb of sun. 



faculae were first seen on the east limb, and also a maximum 11 

 to 13 days later. There was also a sharp maximum when faculse 

 were first seen on the west limb of the sun (ii-day on plot) and 

 another maximum 10 to 11 davs earlier. 



FORECASTING FROM SOLAR RADIATION DATA 



The severest test of knowledge is prediction. Our researches give 

 clear proof of a connection between solar variations and weather 

 changes, but at the same time show that the relation is a complex 

 one. The question arose : Is it possible to base weather forecasts on 

 this knowledge, and to what degree of accuracy? Weather forecasts 

 based on observations of solar phenomena were already being tried in 



