EFFICIENCY OF FOG CHAMBER. 



19 



passed through the end of the fog chamber as in table 7. To guard 

 against direct inductive action the fog chamber was covered with an 

 earthed plate of aluminum, 0.5 mm. thick, though this precaution is 

 superfluous. The table shows the distance (D) of the anticathode above 



& B - 



160 



120 



100 



Figs. 15 and 16. Early data of efficient nucleations (A/, n) and coronal diameter (s), 

 appearing at different exhaustions (dp) in dust-free air. Imperfect fog chamber. 

 (Illustrating table 7.) 



the fog chamber, the coronal diameter (5/30), the nucleation (N; n would 

 have no meaning here), and the time elapsing (Lp), after the radiations 

 are cut off until the observations are made. The time of exposure was 

 uniformly 2 minutes. Longer exposures would have produced seriously 



