Nipher—On the Nature of the Electric Discharge. 18 
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 
