at the Electrodes in a Solution. 



75 



through the other side-opening is continued by the rubber 

 tube r. It contains the wire leading to the anode, formed of 

 a piece of pure electrotype copper, which lines the inside of 

 the vessel. This tube also serves to pass hydrogen into the 



r^3 



solution before each experiment. The tube / leads through 

 the lid to the gas-burette. The gas-tight joint //, through 

 which the stirrer passes, will be understood from the figure. 

 It may be described as an inverted cup rotating in a ring of 

 mercury. Glycerine is placed at the top of the mercury, 

 and after the cup had become well moistened with the 

 glycerine it could be made to rotate up to over 500 revolu- 

 tions per minute without any considerable leakage occurring. 

 When rotating at these very high velocities, a very slight 

 escape of the hydrogen contained in the vessel took place ; 

 but this w r as in the nature of diffusion occurring through a 

 porous cup, for it seemed independent of the pressure of the 

 gas, and a correction could therefore easily be made for it. 

 The stirrer s may be described as a modified Witt's stirrer. 

 It has four hollow arms out of which the liquid is thrown by 

 centrifugal force, being replaced by solution drawn from 

 above the cathode. Owing to the great extent to which it 

 causes the liquid in the vessel to rotate, which 'hinders the 



