1909.] THE CORONAS OF CLOUDY CONDENSATION. 183 



question for relative logarithmic currents of the order of .035, 

 the y ray effect is .0010, the conduction leakage smaller than .0001. 

 The other extreme, /. c, the value of d{\og V)/dt for the freely 

 falling needle is about .1 in the same units. Hence it follows that 

 if tlie needle falls faster than would be quite trustworthy, the 

 auxiliary capacity selected is too small. The time interval between 

 observations for V was 4 sec, throughout. 



6. The Same: Coronas. — These results (to be given in Figs. 

 2a and 2) contain the data for the maximum ionizations obtainable 

 with the radium tubelets I., II., III., IV., V. at my disposal. The 

 corresponding corona was a large orange-yellow type, representing 

 (in my former reductions) 506,000 nuclei in the exhausted fog 

 chamber. I have supposed this to be equivalent to 653,000 when 

 the fog chamber is at atmospheric pressure, seeing that the coronas 

 are actually displaced during exhaustion; i. e., at the maximum 

 ionization does not coincide in the position with the largest corona 

 on exhaustion,* but is displaced in the direction of the exhaust 

 currents. The observation would seem to mean that exhaustion 

 is more rapid than the reproduction of ions to restock the region 

 of dilatation. In general this inherent discrepancy of a marked 

 distribution of ionization increasing from end to end of the fog 

 chamber is still outstanding. It is partially allowed for since the 

 observations are made near the middle of the chamber where the 

 average conditions supervene. 



7. The Same: Summary. — The data given in Fig. 2a merely show 

 the fall of potential in scale readings, in the successive observations 

 4 seconds apart, for positive and negative charges. Fig. 2 gives the 

 corresponding positive and negative apparent ionizations. If the 

 two curves between .8 and 1.2 volts be considered, the mean ioniza- 

 tion of each is 



Apparent positive ions (negative charge), A^= 540,000. 

 Apparent negative ions (positive charge), iV'= 1,164,000. 

 Total true ionization, N -{- N' =1,704,000. 



Total nuclei caught, 650,000. 



It will be seen that A'' + A^' is the true total ionization, positive 

 *See papers cited; also Science, XXVIII. , p. 26, 1908. 



