26 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IIO 



which interdiurnal decreases in sea-level pressure ^ 5 mb. had been 

 observed in Frankfurt a.M., and furthermore all 121 days, on 

 which interdiurnal increases in sea-level pressure ^ 5 mb. had been 

 observed at the same station. For these so selected key days, as 

 well as for 11 preceding and 6 following days, average calcium 

 flocculi character numbers have been computed by means of the 

 superposed-epoch method. Moreover, a subdivision of these statistics 

 has been made according to different seasons and to years with in- 

 creasing and decreasing sun activity. The results are represented in 



I SeasonsI 

 1936 - 1938^ 



The Averoge Behaviour of the Character- Figures of 



Calcium - Flocculi (whole sun-oiso related to oil ( 101 ) those 



Days when the Interdiurnal Decrease of Sea-Level 



Pressure ( daily mean) in Fronkfurto.M. was I 5 mb (— ) 



ond to on ( 121 ) those Doys when the Interdiurnal 

 Increase of Sea-Level Pressure in Fronkfurto.M. wos 



s 5 nob ^ ) 



W Winter 1936-1941 



rOctober to i March 1 



-7 -S -3 .1 •! tS ♦S .7 



Day I A(r«r 



-H -9 -7 -5 -3 -I ♦( ♦S ♦S ♦7 



Before Ooys After 



\ / l93j9-[. .. 



V^^^i°>' i ' >3 '.»'«; 



-11-9 

 Before .' Days 



Fia 20. 



figure 20. The similarity between the winter and the summer curves 

 is again striking ; the same is on the whole true for the years with 

 increasing and decreasing sun activity, although even here the tabu- 

 lations are completely independent of each other. Besides, the op- 

 posite course of those calcium curves which were computed for the 

 pressure decreases, and of those calcium curves which were computed 

 for the pressure increases, is rather remarkable. As to the sea-level 

 pressure increases, it can be stated that 3 to 5 days before these 

 increases the calcium flocculi character number likewise increases 

 distinctly, after having been particularly low 6 days before the key 

 dates. This finding is compatible with our previous statement that 

 the sea-level pressure in Frankfurt a.M. shows a maximum 4 to 6 

 days after intense ultraviolet invasions. The assumption made hereby, 



