THE ELECTRON METHOD OF STANDARDIZING THE 

 CORONAS OF CLOUDY CONDENSATION. 



By carl BARUS. 



{Read April 24, 1909.) 



I. Introductory. — Last year I published some preliminary experi- 

 ments^ in which the coronal display of the fog chamber was stan- 

 dardized by aid of the value of Thomson's electron, 10^"^ = 3.4 

 electrostatic units, and of the known velocity of the ions. Later 

 similar experiments were made in terms of the former datum and 

 the decay constants of the ions, though this method is not here to 

 be considered. In the experiments in question a separate leaded 

 condenser was used to determine the ionization, while the nucleation 

 was measured in a cylindrical fog chamber. The data, though nec- 

 essarily rough, owing to the dampness of the room in the summer 

 time, when used for the determination of e by aid of my earlier and 

 independent constants of coronas, nevertheless gave a series of 

 promising values. In the paper cited it was assumed that the whole 

 current due to both positive and negative ions is measured. If, 

 however, the current observed is due to negative ions, while the 

 negative ions only were caught in the fog chamber used, as now 

 appears probable, then the data would be (F denoting the fall of 

 potential per second, dV/dr the average field, all referred to volts, A^ 

 the number of nuclei (negative ions), per cubic centimeter). 



where the velocity of negative ions in a unit field of dry air is taken 

 as z^=i.87 cm./sec. 



^American Journal of Science, XXVI., 1908, p. 87; idem, p. 324. 



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