352 



Mr Townsend, Electrical Properties of [Nov. 22, 



We thus know the weight of each drop and dividing this into 

 the weight of the corresponding cloud, we obtain the number of 

 drops per cubic centimetre. 



Fig. 3. 



When the number of drops is divided into the charge per cubic 

 centimetre the charge on each is obtained. 



The charge on the positive carrier was thus found to be 

 2*4 x 10 -10 , and that on the negative carrier to be 2*9 x 10~ 10 . When 

 we take into account all the experimental errors these two charges 

 may be considered equal and approximately 3 x 10 -10 . The charge 

 on the hydrogen was found to be between one-third and two- 

 thirds of this value but could not be arrived at very accurately 

 owing to the difficulty of finding the size of the drop. For present 

 purposes this charge will be taken as § x 10 -10 . 



Velocity of the cannier when acted on by an electric force. 



(8) It has been shown that the radius of the drop forming the 



cloud is in the case of negatively charged oxygen 810 -5 , so that 



its weight is 210~ 12 grammes and when acted on by gravity, it 



moves at the rate of 18 millimetres in four minutes. The force 



acting on the drop is practically 210 -9 , so that it would require 



210 -9 

 an electric force of s — tt<z:^ absolute units to produce an equal 







3 x 10 



velocity, or 2000 volts per centimetre 



As we are only dealing 



