472 Mr Edmonds, On Quasi- Radio-activity 



To further test this point, connections were made both with 

 the open air and a water pump, by which air could be sucked 

 through a long lead composition pipe, earth connected, over some 

 phosphorus pentoxide, and through a long glass-wool plug into 

 the box, which thus became filled with pure dry air free from 

 dust. 



On causing the discharge to pass between points and disc in 

 this air, practically the same effect was produced as when the box 

 had been closed for some time, the deflection produced when the 

 discs were placed respectively in the testing vessel being 2'5 

 divisions, the sign of electrification of the disc having no effect 

 whatsoever in altering this deflection. 



The same results were obtained for similar experiments to the 

 preceding when the points were made of other metals — brass and 

 copper — suggesting that the phenomenon noticed is not a property 

 peculiar to one of the metals. 



By a slight modification of the apparatus it was possible to 

 ascertain if any activity had been induced upon the points, but 

 no difference could be ascertained between the rates of leak 

 obtained with or without the points being connected to the 

 electrometer quadrants, which were charged up to the potential 

 of one Clark standard cell for purposes of testing. 



The capacity of the apparatus was measured by carefully 

 insulating it on paraffin wax blocks, and comparing it with the 

 capacity of an adjustable standard air condenser, and was found 

 to be, in electrostatic units, 7*5 cms., for the voltage used through- 

 out the experiments.' 



In the first series of experiments, in which this quasi-radio- 

 activity was shown, the deflections rose to one-half their final 

 value at the expiration of 2 minutes from the start, so that the 

 discs were giving off ions during that time at the rate of 110 per c.c. 

 per second for the positive leak, and 121 per c.c. per second for the 

 negative leak. 



A series of experiments were made, in which different times 

 were allowed to elapse between the passing of the discharge and 

 the testing of the discs, and it was found that the various discs 

 lost their activity almost entirely at the expiration of an interval 

 of 3 hours between the two operations. 



These experiments show that this quasi-radio-activity, pro- 

 duced by the action of the point discharge, is due to the presence 

 of dust particles in the air. These dust particles come into 

 contact with the stream of ions present, moving from the points 

 to the plane, carrying the discharge, and, when they become 

 deposited on the plane, trap some of these ions, and hold them, 

 so that they can only enter very slowly indeed into the metal 

 of the disc under the force of attraction they experience by virtue 



