﻿excited by the Alpha Rays from Polonium. 



833 



a distance of about 6 mm. The polonium, which was carried 

 by the electrode B, could be made to face in any direction by 

 turning the axial rod A. This rod passed through, and was 

 sealed to, a glass tube J), which fitted over another glass 

 tube E, so arranged that the joint could be covered with 

 mercury and so made air-tight. The electrode C, which was 

 made of carbon, was connected with the quadrant of an 

 electrometer, the connecting rod passing through an ebonite 

 plug fitted into the side of a vessel by a side tube F. Another 

 side tube Gr connected the vessel to the McLeod gauge and 

 the Gaede pump. The vessel itself, which was a cylindrical 

 brass tube about 5 cm. in diameter and 8 cm. in length, was 

 connected to earth. All joints were made air-tighfc by means 

 of wax and solder. 



The first experiment was conducted as follows. A fresh 

 carbon electrode was placed in the apparatus, the polonium 

 was turned away from the electrode, and the air was pumped 

 from the vessel for over an hour with the pump going con- 

 tinuously. Then the polonium was charged to a positive 

 potential of 80 volts, and turned so that it faced the carbon 

 electrode. A reading was at once taken of the rate at which 

 the carbon electrode charged up, and similar readings were 

 made at suitable intervals of time afterwards. The results 

 obtained are given in Table XIT. 



Table XII. 

 Fresh carbon in apparatus. 



Turned polonium to face carbon 1 hour 20 minutes after 

 pump was started. Voltage on polonium=80 volts. 



Pressure of air in 



vessel. 



Time from initial 



reading taken lh. 20 m. 



after starting pump. 



Current to 

 electrode. 



•<-001 mm. 

 <-001 „ 



<-ooi „ 



<-001 „ 

 -c-001 „ 



minutes 



5 



15 

 30 

 60 „ 



122 

 123 

 124 

 122 

 123 



These results show that there was no sign of a " fatigue " 

 in the rate at which the carbon electrode charged up with 

 the time, for the rate was practically constant throughout all 

 the readings. 



Phil Mag. S. 6. Vol. 23. No. 137. May 1912. 3 I 



