70 200 



74 100 



nn iqq y still lower pressure. 



Rays of Posit ice Electricity. 42t> 



Deflexion of Electroscope Potential Difference in volts 

 per minute. between the plates. 



6 200 ^ 



7 200 | Pressure so high that 



6 100 )■ spot was only just 



6 200 j visible on the screen. 



6-5 100 J 



16 200 } 



15 100 -p. ...., , 



,,. qq y Pressure a little lower. 



16 !"'."."'.".".!!!."! 100 J 



} 



CO 200 J 



12 200 1 



10 100 



12 200 V Much lower pressure. 



11 100 j 



12 100 ; 



The fact that the current between the plates was saturated 

 by the potential-difference used to deflect the Canalstrahlea 

 is confirmed by the fact that the electrostatic deflexion of 

 the Canalstrahlen is proportional to the potential-difference 

 between the plates ; this would not be the case unless the 

 current were saturated. 



It follows from these results that the electric force deflect- 

 ing the Canalstrahlen was the same when the pressure was 

 very low and the potential-difference between the electrodes 

 40,000 volts, as it was when the pressure was higher and the 

 potential-difference only 3000 volts; and therefore that the 

 constancy of the deflexion in the two cases implies that the 

 velocity of the particles was the same. 



It thus appears that when the pressure is high the velocity 

 of some of the positively charged particles is greater than 

 that which could be imparted by the electric field as the 

 particles move from the place where they are liberated up to 

 the cathode. 



The place where the positively charged particles are pro- 

 duced can, by observation of the shadows thrown by obstacle- 

 placed in front of the hole in the cathode, be shown to be 

 the region near the boundary of the dark space ; thus, if the 

 particles when liberated were positively charged, the velocity 

 they would acquire from the electric field would be that due 

 to a fall through the dark space; hence if this were the 

 source of their velocity, a passage back through the dark space 

 from the cathode to the anode would bring them to rest at 

 the boundary of the dark space, and they would not travel 

 any further down the tube. 



