352 



C. Bar us — Large and Small Coronas. 













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LEGENDS FOR FIGURES. 



Curve 1.— Periodicity of dust-free air, showing the angular apertures of 

 coronas (ordinates s) in successive identical exhaustions (numbered by 

 abscissas), made at two-minute intervals apart. Note that high (h) inferior 

 coronas are usually followed by low (I) superior coronas and vice versa ; 

 while high superior coronas are followed by high inferior coronas. dp=31 -2 cm . 



Curve 2. — The same for three-minute periods between the exhaustions. 



Curve 3. — The same for five-minute periods. Periodicity gradually 



Curve 4.— Periodicity of dust-free air energized by radium (10,000 x ) in 

 glass, within the fog chamber. The successive exhaustions gradually 

 reduce the nucleation. Sequences of h and I are apparent. The ordinates 

 are number of nuclei per cm 3 . 6p=25 cm . 



Curve 5. — Dust-free air not energized, showing the reduction of nuclea- 

 tion (decreasing apertures, s) in the lapse of time. 



Curve 6.— Periodicity of apertures (s) at different pressure differences dp. 

 The number of the exhaustions is attached to the observation. The loci of 

 inferior and superior coronas are well marked. 



Curve 7.— The same computed for number of nuclei (N) in one cub. cm. 

 of air at normal pressure. 



