the Eledrical Dischavye from a Point to a Plane. G19 



is passintij, it is possible to ascertain whether any particles 

 Uiroer than ions are being produced : it may be noted that 

 the presence ot* positive ions cannot be detected by this 

 method, if negative ions are also i)resent. 



Apparatus and General Results, 

 The form of the apparatus eventually found most suitable 

 is drawn approximately to scale : the electrical connexions are 

 merely represented diaoTammatically. 



The discharge passed between a point and the water surface 

 in the bulb A, which was connected by a sealing-wax joint 

 to the expansion apparatus below, to the apparatus for regu- 

 lating the pressure, and to the aspirating bottles for filling 

 with the required gas. The measuring tubes being full of 

 mercury, the tube h was pulled beneath the surface of the 

 water in the bottle B containing the gas, and water allowed to 

 flow into the bulb and expansion-tube below. The wii-e bearing 

 the point was then inserted into the side tube C, by means of 

 sealing-wax, the tube b pushed up into the gas, and the piston 



