I9I2] 



Secondary Rays Excited by the Alpha Rays. 



165 



Table VIII. 



Fatigued carbon electrode. 



Hydrogen in Apparatus. 



Charge on pol. = 8o volts. 



Next the apparatus was filled with hydrogen at atmospheric pressure 

 and left standing for eighteen hours. A series of readings was taken as 

 before and is given below. 



Table IX. 



It will be noticed that in these two last experimentswith the hydro- 

 gen the first reading was taken four minutes after the pump was started 

 while in the three experiments with the air the first reading was taken 

 seven minutes after the pump was started. The reason for this was that 

 the pump reduced the pressure of the hydrogen much quicker than the 

 air and it was desired to take the first readings for both hydrogen and 

 air at approximately the same pressure. 



From the results given in the last two columns of Tables VIII and IX 

 the two lower curves of Fig. 5 are plotted, while the upper curve of Fig. 

 5 is plotted from the results given in the last two columns of Table V. 

 The latter curve pictures the way in which the rate of charging of the 

 fresh carbon electrode decreased with the time, while the former curves 

 shew how the rate of charging of the fatigued carbon electrode, which had 

 been left in hydrogen at atmospheric pressure, decreased with the time. 



It will be noticed that there is hardly any drop in the lower curves 



