362 Mr Townsend, Electrical Properties of [Nov. 22, 



not from an increase of the charge on the carriers already present ; 

 for, if the increase in density were due to an increase in p, we 



would have found — — ° to be proportional to the square of p . 



r 



(18) It would be almost impossible to arrange to pass the gas 

 along a tube in such a way that the discharging power would be 

 as small as the theoretical value, calculated from the numbers 

 given for k, section 13. Small differences in temperature between 

 the gas and the sides of the tube, and other effects which would 

 give rise to currents in the gas, considerably increase the dis- 

 charging power, but have a comparatively small effect on the loss 

 of charge when the gas is allowed to stand in the tube. The 

 velocity of the carrier towards the sides of the tube, due to an 

 electromotive force, will on this account be too large when calcu- 

 lated from the formula Po ~ ^ = -^— . ^— . 



p k q 



Thus, when we substitute the values given in §§ 10, 11 for 



— and p , we obtain for K the values : 



P 



K ff =S.e B , 



Causes which influence the discharging power. 



(19) In the above experiments the gases were always treated in 

 the same way before entering the tube C, being bubbled first through 

 a solution of potassium iodide and then through strong sulphuric 

 acid. When the gases are bubbled through water instead of sul- 

 phuric acid they will enter G carrying with them a cloud, the 

 effect of gravity upon which makes itself very apparent by com- 

 paring the charges acquired per minute by the tube, when in the 

 vertical and horizontal positions. Thus in the case of a stream of 

 highly charged hydrogen, which bubbled through water before 

 entering G, it was found that the charge acquired was 14 scale 

 divisions per minute as the gas passed through G in the vertical 

 position ; and 47 divisions per minute with C in the horizontal 

 position. The electric capacity of the conductor, consisting of G 

 and the quadrants, was uot altered by more than 3 per cent, by 

 turning the tube round ; so that the large increase in the dis- 

 charging power must have been caused nearly entirely by the 

 force of gravity acting on the drops forming the cloud. The 

 experiment shows that the charge resides on the drops forming 

 the cloud. 



