58 Trans. Acad. Sci. of St. Louis. 
part a disruptive spark discharge. This is accompanied 
by a streaming in of the negative fluid from various 
directions over the film. See Plate XVIII, Fig. B, and 
Plate XIX, Fig. A. In the negative line the copper plate 
is in the case shown in Fig. 1 energized by a compression ~ 
Fic. 1. 
action from the machine terminal. The discharge from 
the film is urged towards and into the grounded line. . 
The flow lines resemble a system of rivers and tributary 
streams. 
In the positive line the terminal resting on the film is 
in a condition which may be described as an exhaust con- 
dition. The electric fluid is then drawn into the pin-head 
terminal from the film. The stream lines in this case 
certainly originate at the pin-head terminal, and elongate 
in a direction opposite to that of the flow. Possibly this 
may be true of the plate in the negative line also. The 
results seem to be alike in character. The action is, how- 
ever, different, and it may be that there is a difference in 
degree. There is in both cases a condenser effect. In 
Plate XVIII, Fig. A, and Plate XIX, Fig. B, are shown 
