ELECTRON METHOD OF STANDARDIZING CORONAS. 



69 



58. Data. High ionization. Currents. The following tables con- 

 tain the mean potentials V, the positive and negative logarithmic cur- 

 rents d(\og V)/dt (apart from the constant), the apparent nucleation N 

 positive and N' negative, computed from these data and the additional 

 information at the head of the tables. In most of the cases the corre- 

 sponding logarithmic currents due to rays outside the fog chamber was 

 carefully measured in the same units by placing a short hard rubber rod 

 between the end t of the aluminum tube (fig. 19) and the wire leading to 

 the electrometer. This cuts out the fog chamber, but leaves the whole 

 remaining circuit undisturbed. 



Similarly the leak value of d (log V) jdt in the absence of radium and due 

 to mere conduction of moist parts is always quite negligible. Thus in the 

 first part of table 23, for relative logarithmic currents in the order of 

 0.035, ^e y ray effect is o.ooio, the conduction leakage smaller than 

 o.ooo i. The other extreme, i. e., the value of d(log V)/dt for the freely 

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

 first part of table 23 the needle falls faster than would be quite trust- 

 worthy, therefore the auxiliary capacity selected is too small. 



Moreover, the negative current only is here measured, as the indis- 

 pensable need of measuring both currents was not then apparent. Hence 

 in the second part of table 23 the measurement of both currents is under- 

 taken. At the same time the capacity of the condenser has been increased 

 to give the needle the necessary slow descent. The time interval between 

 observations for V is 4 seconds in both parts. 



TABLE 23. Number of ions per cm 3 . Cylindrical condenser fog chamber. Capacity 

 of system: small auxiliary condenser, 330 cm. ; electrometer and wire, 69 cm. ; fog 

 chamber, 11.4 cm.; total, 410 cm. Fog chamber: glass 2R } = 13. 4 cm.; aluminum 

 core, 2.^2 = 0.635 cm.; / = 3g.5cm. Velocity of ions: u= 1.37 cm./sec.; v= 1.51 cm. /sec. 

 in field of volt/sec; e = 3.4Xio~ 10 . Current due to f-rays without: d (log V)/dt = 

 o.ooi; current due to conduction leakage d (log V)/dt = 0.000081. Accelerated free 

 fall of needle, d (log V)/dt = o.o6 to 0.16 for corresponding deflections. Time interval 

 4 sec. Radium I + II + III + IV + IV' + V. K = 76Xio 6 . Cm. of scale equivalent to 

 0.0585 volt. 



