106 Dr. J. C. Beattie on the Electrification of 



foil was negatively or positively electrified. The electrifi- 

 cations were less than those obtained with the uranium bare. 

 For example, with the uranium wrapped in aluminium foil 

 kept at + 2 volts and the lead cylinder connected to sheaths, 

 or with the first to sheaths and the cylinder at — 2 volts, the 

 air when drawn through the filter raised it to a potential of 

 -J-'ll of a volt per minute of pumping. With +10 volts, 

 the potential per minute of pumping was +0 - 05 of a volt, 

 with 95 volts, +*015 of a volt per minute. The negative 

 electrifications of the air with the uranium wrapped in alu- 

 minium foil kept at —2, —10, or —95 volts, and the metallic 

 cylinder to the sheaths of the electrometer, were smaller than 

 the corresponding positive electrifications given above for 

 + 2, + 10, and + 95 volts. 



Finally the uranium was placed inside a paraffin cylinder. 

 Round the outside of this cylinder tin-foil was wrapped. 

 With both uranium and tin-foil connected to case — arrange- 

 ment (a) — there having been no previous electrification of 

 the uranium in the paraffin cylinder, the air drawn from the 

 cylinder showed no sign of electrification. 



With arrangements (b) and (c) similar results were ob- 

 tained to those found when the cylinder used was of metal, 

 with this difference, however, that the amount of electrification 

 with any given voltage depended on the voltage which had 

 been used in the experiment immediately preceding. For 

 example, after the tinfoil round the cylinder of paraffin had 

 been connected to the positive terminal of the battery, and 

 the uranium to sheaths, it was found that the air drawn 

 through the filter raised it to a potential of —'235 of a volt 

 per minute of pumping. In the succeeding six minutes, 

 while the tinfoil was kept at — 10 volts, and the uranium to 

 sheaths, the electrometer deviation was equivalent to a rise in 

 potential of the filter of +"7 of a volt per minute. In the 

 succeeding two minutes the rise of potential was +'6 of a 

 volt per minute, and six minutes later it was + '3 of a volt 

 per minute. 



Both uranium and tinfoil were next connected to sheaths 

 — arrangement (a) — and in the first two minutes of pumping 

 the rise of potential of the filter was — *G of a volt per minute. 

 In the second two minutes the rise was only — "13 of a volt 

 per minute. 



With the uranium connected to sheaths and the tinfoil at 

 + 10 volts, the air was found to be negatively electrified ; the 

 amount of this electrification was such as to raise the potential 

 of the filter — "65 of a volt per minute in the first minute and 

 — *2 of a volt per minute in the tenth minute. 



