﻿Periods of Transformation of Radium. 73 



electrode, with about 100 volts less than when the untreated 

 electrode was employed. It was further very noticeable 

 that, using the treated electrode and gradually reducing the 

 voltage, a much fainter luminosity of discharge could be 

 obtained without actual extinction of the discharge than was 

 the case when the untreated electrode was employed, in 

 which case the transition from a visible discharge to no 

 luminosity was much more abrupt. This fact goes to show- 

 that the differences in the minimum voltage required to pro- 

 duce a visible discharge in the two cases was actually due to 

 the presence of radium, and not to any slight difference in 

 the distances between the electrodes or other want of symmetry 

 in the tube. 



A d'Arsonval mirror galvanometer was next inserted in 

 the circuit. With a plain alternating current this galvano- 

 meter would, of course, give no deflexion. It was, however, 

 found that whether the radium treated or the untreated elec- 

 trode was used, there was always a slight deflexion of the 

 galvanometer, due no doubt to some unidirectional valve action 

 on the part of the vacuum-tube. It was found, however, that 

 using the treated electrode, the galvanometer deflexion was 

 between two to three times as great as when the untreated 

 electrode was used, tins being evidence that the presence of 

 radium increased the valve action to a considerable extent. 



The thermo- galvanometer was next substituted for the 

 d'Arsonval mirror galvanometer, and it was then found that. 

 using the radium treated electrode, the amount of current that 

 passed through the tube was from one and a half times to 

 twice as large as when the untreated electrode was employed. 

 this showing that the presence of radium on the cathode 

 materially increases the amount of current that passes through 

 the tube with any given voltage. 



The writer is indebted to Mr. J. C. M. Stanton and 

 Mr. R. C. Pierce for their assistance in making the above 

 investigations. 



XII. On the Periods of Transformation of Radium A. B, 

 and C, By Howaed L. Beonson, Ph.D.* 



THE present investigation was originally undertaken in 

 order to determine whether or not radium A was the 

 parent of radium B. Rutherford (Phil. Trans. 1901, p. 198) 

 had previously pointed out that the experimental /3-ray curve 

 seemed to agree better with the theoretical curve calculated 

 on the assumption that the products A and B were not 



* Communicated by Professor E. Rutherford, F.E.S. 



