40 ; Mr. J. A. McClelland on the Conductivity of 



In the experiment the electrometer showed a positive 

 charge rising rapidly to a value at which it remained 

 constant. This was because the conducting gas entering B 

 caused a discharge to A, and equilibrium was produced when 

 the discharge was equal to the gain of positive electricity 

 from the carriers. 



Fig. 6. 



EARTH 



This experiment is difficult to explain except on the theory 

 that the negative carrier moves faster than the positive under 

 the same force. As the charges of the positive and negative 

 carriers are probably the same, the positive carrier must have 

 more uncharged particles attached to it. 



5. Change in the Velocity of the Carrier. 



In all the experiments described above on the velocity 

 with which the carrier moves under an electric force, the 

 experiments were made on the gas at a short interval after it 

 left the flame and when its temperature was always well over 

 100° C. Further experiments showed that this velocity does 

 not remain constant, but falls away rapidly when the gas 

 has cooled down at a distance from the flame. The gas is 

 drawn up a tube with a number of terminals placed along 

 this axis at different distances from the flame, so that the 

 velocity of the carrier can be determined at each of these 

 points. Knowing the velocity of the current of gas up the 

 tube, we know the time which has elapsed since it left 

 the flame ; and the temperature can be found by inserting 

 thermometers. 



