STANDARDIZATION OF FOG CHAMBER. 



57 



7; let C (electrostatic units) be the capacity of the electric system, con- 

 denser, and electrometer, together with such auxiliary capacity as may 

 be inserted to get a leakage of proper value. Let U be the efficient* 

 velocity of the ions, positive or negative as the case may be, in a field of 

 i volt per centimeter, V the voltage and V the change of voltage per 

 second. Finally, let N be the nucleation caught when the identical 

 condenser core is placed in the fog chamber. Then for the cylindrical 

 condenser (if natural logarithms be taken), 



ClnRJR 2 V 

 '' 6oo7tlUN V 



If V is small enough to keep V/V constant, the curves show this at 

 once. Rough tests, using the old data of my fog chamber, led to values 

 about as shown in table 20, where the irregularities are in the electro- 

 meter, due it was supposed to the connecting wires, which were not at 

 the time surrounded by earthed pipes. It has been assumed that relative 

 ions only are caught in the fog chamber and that a negative current only 

 is observed. The e so found is too large. 



TABLE 20. Preliminary values of e. Wires not surrounded by pipes. 



_ClnR l /R, V/V 

 6oonlU N 



C=i3o; [7=1.87 cm. /sec. (neg. ions); F<o.5 volt; field 0.7 volt/cm.; N 210,000 

 per cm 3 (neg. ions); 2/^ = 2.1 cm.; 2R 2 = o.62 cm.; /=i8.2 cm. 



*Same with N = 185,000 per cm 3 (neg. ions). 



46. The same. Wires surrounded by earthed pipes. In order to 

 make use of the high sensitiveness of the Dolezalek electrometer, the 

 wires were now surrounded, so far as possible, with pipes of galvanized 

 iron, 2 inches in diameter, put to earth. Under these circumstances there 

 was less irregularity, though the current still continued to be far from 

 proportional to the voltage, even for low values of the latter. It will 

 not, therefore, be worth while to give a detailed account of V/V, and the 

 mean value for a field of i volt per centimeter was taken, as found from 



*If one shell of the condenser is put to earth, positive or negative currents only are 

 measured and not the whole current. 



