1909] THE CORONAS OF CLOUDY COXDEXSATIOX. 185 



close together; but such errors necessarily compensated each other 

 in the mean values. 



10. Data: Moderate Ionization: Electrical Currents. — These re- 

 sults were obtained by placing but one radium tubelet, No. IV., in 

 the aluminum tube tt' of the condenser-fog-chamber. The data 

 were found in the same way as in the above. N = Kd{\ogV)/dt, 

 as usual. 



Both positive and negative currents were observed in succession 

 and the true total ionization is N -\- N' as before. Moreover, the 

 capacity of the condensers were widely varied, 410 to 1,459 cm., 

 without showing serious divergences. 



11. The Same: Coronas. — At a fall of pressure of 21 cm. (and 

 somewhat below) or 8/)/^ = .27, the nucleation was stationary and 

 equal to A' =113,000 in the exhausted fog chamber. At atmos- 

 pheric pressure therefore 113,000X1-37=154,000 nuclei should 

 have been present. The effect of a charge on the core of the con- 

 denser did not appreciably diminish the nucleation. 



12. The Same: Summary. — The successive observations in scale 

 parts at intervals, 30 seconds apart, are shown in Fig. 3a, the slopes 

 only being of interest. The apparent values of N are given in Fig. 3. 

 All the four series show about the same drift, even though taken 

 many days apart. The condenser effect (excessive rapidity of 

 needle) may be considered eliminated for capacities greater than 

 500 cm. 



By averaging the ionizations between V^.6 and V^^i.24. in 

 both curves the data found are as follows : 



Apparent negative ions. A'' = 278,000. 

 Apparent positive ions, N' = 107,000. 

 True total ions, N -}- N' = 385,000. 

 Total nuclei, 180,000. 



Hence about 47 per cent, of all the ions were caught on exhaustion, 

 if the values of u, v, e, N, inserted, are correct. Supposing that 

 negative ions only are caught in the above fog chamber, the value 

 of the electron would be 



io"^ = 3.4 X 2.14 X 2 = 3'^ electrostatic units. 



