88 Mr. Richardson on the Positive Ionization produced 



volts, whilst the second wire, which was earthed, was kept 

 at a red heat for 15 minutes. On allowing evervthing to 

 cool and stand for a short time, and again heating the first 

 wire with '241 ampere, the following values of the cnrrent 

 were obtained with + 200 volts (the units of current are the 

 same as before") : — 



Current (+ leak). 



Heating current (amps.). 



2250 



2810 



91 



136 



•241 

 •241 

 •224 



•2.37 



The activity induced by the second hot wire is in this case 

 enormous compared with the greatest current (46) due to the 

 activitv which the hot wire originally possessed. 



The above readings for the current were taken at intervals 

 of about 6 minutes, so that it is evident that the value of the 

 induced positive leak falls off very rapidly with the time 

 when the wire is heated. In other words the induced activity 

 is almost all driven off in about half-an-hour, and in some 

 cases even less. 



This effect is not due to ions which remain suspended 

 inside the bulb, or to any effect produced on the walls of 

 the tube by heating, for absolutely no leak was obtaine*^! 

 when the first wire was cold, it is also evident from the 

 above experiments, and from others which will be described 

 later, that the effect persists for a considerable length of 

 time. 



Each time the experiments were repeated the induced 

 activity was found to become continuously smaller and higher 

 temperatures had to be employed to show the effect. This 

 is probably due to the substance which causes the effect 

 becoming diffused onto the waUs of the tube and the cold 

 parts of the electrodes, since it goes hand in hand with a 

 falling off" in the conductivity produced when the first wire 

 alone is heated to still higher temperatures. 



Three experiments were now made to see if the effect could 

 be produced by merely charging up the first wire to a 

 suitable potential, the second being cold and put to earth. 

 The wire was charged to + 200. 0. and —200 volts respectivelv 

 and left for 40 minutes each time : but the conductivity was 

 again found to be zero on heating to the original temperature. 



