586 Mr. A. E. Garrett on Positive Electrification 



electrometer and a potential difference of 314 volts was used 

 This is shown by the following Table : — 



Volts. 



Current due to 

 positive ions in 

 Arbitrary Units. 



Volts. 



Current due to 

 positive ions in 

 Arbitrary Units. 



42 



46 



390 



130 



84 



58 



432 



130 



126 



75 



474 



128 



168 



85 



516 



130 



210 



95 



558 



126 



236 



111 



608 



130 



275 



123 



656 



130 



314 



130 







348 



130 







Under the conditions of experiment (velocity of air through 

 the tube being 40 cms. per sec.) it can easily be calculated 

 from the formula 



(& 2 -a 2 )log c &/<* 



2W 



in which 



v = velocity of ions in cms. per sec, 

 /> = radius of the tube, 

 a == radius of wire electrode, 



V = potential- difference in volts between wire and tube, 

 £ = time taken by air to pass from one end of the elec- 

 trode to the other, 



that all ions with velocity greater than O0027 cm. per sec. 

 are withdrawn when the saturation voltage of 314 volts is 

 put on. When the voltage is raised to 656, ions must have 

 a velocity less than 0*001 cm. per sec. to be able to escape 

 from the first tube. 



If the front electrode (i. e. one nearer the heated salt) is 

 earthed and the front tube kept at any positive potential 

 greater than 320 volts, no current should be found near the 

 back electrode when this is connected with the electrometer, 

 and the back tube raised to any positive potential ; a current 

 could, however, be detected. 



Even when both tubes were raised to a positive potential 



