328 C, Barns — Thomson } 3 Constant. 



Thus with a correction for the external gamma radiation, 

 the data for e show reasonable values, in spite of the simplicity 

 of the experiment. It follows, therefore, that even in the 

 case of such large numbers of ions as occur in these experi- 

 ments (over 500,000), both positive and negative ions must 

 have been caught in the fog chamber and that the constants of 

 coronas used heretofore are substantially correct. In case of 

 the last value £Xl0 10 = 2'5, for the small capacities of 17 cm , 

 the aluminum leaves on the electroscope converge too rapidly 

 for measurement, so that the air resistance may have produced 

 an appreciable discrepancy. Hence both i and e are too small. 

 ISTo refinement has been attempted in these experiments, their 

 chief purpose being to test the standardization of the fog 

 chamber in terms of coronas and the degree to which positive 

 and negative ions may be caught even at very high nucleation. 

 One may note in conclusion that the currents of the order of 

 ^=77 electrostatic units or 2*6 XlO 10 amperes, are already quite 

 within the reach of the sensitive galvanometer." 



My thanks are due to Miss L. B. Joslin, for assistance 

 throughout this investigation. 



Brown University, Providence, R. I. 



