THE 



LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENC 



[SIXTH SERIE& 



AUGUST 1905. 



XXV. Charge carried by the a, and j3 Rays of Radium. By 

 E. Rutherford, F.R.S., Macdonald Professor of Physics, 

 McGill University, Montreal* . 



IN the Bakerian Lecture (Phil. Trans. A 204. pp. 169-219, 

 1904), I gave an account of some experiments made in 

 order to measure the charge carried by the a rays, with a 

 view of determining the number of u particles shot out per 

 second from a given mass of radium. The method employed 

 is clearly shown in fig. 1. A known small quantity of pure 



Fk. 1. 



radium bromide was dissolved in water and the solution 

 spread uniformly on a metal plate A, and then evaporated to 

 dryness. The process of solution and evaporation liberates 

 the radium emanation and about three, hours afterwards 



* Communicated by the Author. A brief account of the results included 

 in this paper was published in a letter to ' Nature,' March 2, 1905. 



Phil. Mag. S. 6. Yol. 10. No. 56. Aug. 1905. O 



