Nipher—On the Nature of the Electric Discharge. 13 



shown in Plate III. This is what is required by the two- 

 fluid hypothesis. The result actually produced is shown 

 in Plate V. This effect presented on this plate seems 

 entirely inconsistent with the two-fluid theory. 



Assuming the one-fluid theory the result shown on 

 Plate V may be explained as follows : 



The electric current is flowing from the ground to the 

 positive terminal of the machine. The condition within 

 the wire may be described as one of rarefaction, such as 

 exists on the exhaust side of a pump. Electricity is leak- 

 ing into this wire from the photographic film, and it is 

 leaking up from the grounded wire below the center of the 

 plate, to the under surface of the plate. The inflow over 

 the film to the wire, is repelled from the central area 

 which is being charged by the grounded wire below. The 

 electricity streams to the wire around this area. The 

 electricity distributed over the lower face of the glass 

 plate, tends to flow upward through the plate, to replace 

 the charge which has streamed from the upper surface to 

 the wire. The grounded wire is now a line of leakage 

 into the discharge wire. The fogging shown on the center 

 of Plate V is due to the upward discharge from the 

 grounded line. This is shown by the two figures of 

 Plate VI. These figures show two photographic 

 plates which were placed back to back. The plate shown 

 in Fig. A was placed with its film in contact with the dis- 

 charge wire when the positive discharge was sent 

 through it. The film of the other plate faced downwards 

 towards the end of the grounded wire. The upper plate 

 shows no trace of a fogging effect. The upper film may, 

 however, be fogged on its under side if the time of ex- 

 posure is increased. If the upper discharge wire is raised 

 from the film, both films may be strongly fogged from a 

 pointed wire below, when no trace of any effect from the 

 discharge wire itself is observable on the upper surface 

 of the upper film. Such a result is shown in the two fig- 

 ures of Plate VII. The fogging shown on the upper plate 



