ELECTRON METHOD OF STANDARDIZING CORONAS. 67 



A special key was provided whereby C' could be switched into the 

 electrometer system or out of it and put to earth. Hence in a series of 

 successive discharges 



(C" + c)V= (C" + C' + c) V (C" + c)V'= (C" + C' + c) V" , etc. , 



so that for n discharges, if the residual potential is V n 



from which the total capacity C = C" -f C' + c is determinable in terms 

 of C' . The results were 



Positive charge C"+ C'+ c= 1445 1443 1422 



Negative charge C"+ C'+ c= 1482 1480 



Mean C= 1459 



the experiments alternating from positive to negative charge, because 

 of the marked drift by the electrometer system when isolated from the 

 cell, as already specified. To measure the small capacities c of the fog 

 chamber, the same method with ten discharges suffices, if C" is excluded 

 and C' retained. Thus the data were successively found, 



+ Charge c=n.S I2 -4 12.2 12.9 



Charge c=io.8 10.4 n.i 11.5 



Mean c=n.3 11.4 n.6 11.2 



eliminating the drift in the final mean =11.4. 



Since the capacity c in terms of the effective internal radius R 3 and 

 external radius R r and lengths / of the cylindrical condenser may be 

 written 



i i R^ i_ 



7 RZ 2X2. T,XC 



the constant c furnishes a mean value for the factor on the left. The 

 ratio of 4.6^ to the measured value of (log R/R z )/l was 0.568, a reduction 

 factor used throughout the tables below. 



57. Method pursued. If C is equal to C"+C' + c we may write the 

 equation for the negative ionization N (positive charge) 



_ C\nR 1 /R z d(\nV) d(\nV) 



i V ~ ; ~ K 



600 TT Ive dt dt 



where R lf R 2 , and / are the effective radii and length of the condenser, 

 io 10 <?=3.4, z;=i.5i cm. /sec., and li^i.^j cm. /sec., the velocity of the 

 negative and positive ions in the unit field, volt/cm., and in case of moist 

 air. The factor (lnR l /R^)/l is replaced by C/2, as specified in section 56, 



