8o CONDENSATION OF VAPOR AS INDUCED BY NUCLEI AND IONS. 



70. Data. Origin of the electrometer current. The seat of the chief 

 electromotive force or charging current in the electrometer follows 

 from the following data, summarized in fig. 27, in which the capacities 

 C, C', C", fig. 26, are successively removed. The currents increase in the 

 same ratio as the reduction of capacities, E being that of the electro- 

 meter. The data are, potentials in scale parts (where i cm. is equivalent 

 to 0.0595 volt), V a being the fall per second: 



The change of voltage throughout the main contours of the curves 

 is almost a linear variation with the lapse of time, except that at the 

 beginning the motion is accelerated from rest as usual; for instance: 



Time o 



V a o 



3 



12 16 20 24 28 32 60 sec. 



3-7 6.1 8.7 ii. o 13.4 15.5 3i.ocm. 



It is the linear character of these curves that greatly simplifies the 

 following measurements. 



TABLE 24. Measurement of ionization N, and voltaic contact difference V c . Time 

 intervals 4 sec. Aluminum-brass condenser. / = so cm., a/?, = 2.01 cm., 2^2 = 0.634 

 cm. Scale part cm. =0.0588 volt. Radium I, II, III, IV, V in aluminum tube. 

 N= i, 750,000; F c = 6.37 cm. or 0.375 volt. 



* After additional 60 sec. 



