Nipher—On the Nature of the Electric Discharge. 3 
famous experiment on the electromagnetic effect due to 
the motion of a charged body, establishes the fact that a 
positively charged body, moving in space, produces the 
same electromagnetic field as a negatively charged body 
moving along the same path with equal velocity in the op- 
posite direction. These two actions are, however, not 
identical, since they involve the motion of masses of mat- 
ter in opposite directions. : 
The positive luminiscence in the Geissler tube is not 
necessarily a discharge of positive electricity, although 
it seems to proceed from the positive terminal. J. J. 
Thomson found that this positive luminescence in a tube. 
15 meters in length moved outward from the positive 
terminal, with a velocity somewhat more than half that of 
light. But this may only be a result of the negative dis- 
charge. A stream of water issuing with great velocity 
from a pipe may wear a channel into the earth, and this 
channel may lengthen for a time in the direction of flow. 
At a distant point where this stream runs down a steep 
bank into the sea, a channel may also be worn, which may 
elongate indefinitely in a direction opposite to that in 
which the stream flows. The gradual recession of the 
falls of Niagara is an illustration of such action. 
If the water were invisible, and if the recession of 
Niagara Falls from Lake Ontario to Lake Erie should 
occur in ten minutes, the phenomenon might be thought 
to be a ‘positive discharge’’ into Lake Erie. 
The positive luminescence in Thomson’s long tube may 
be explained as follows: 
The ikonization of the column of gas at the anode end. 
begins at the anode wire. Negative particles pass from 
molecules in contact with it to the wire. These molecules 
thus ikonized are then capable of accepting negative par- 
ticles from their neighbors who are slightly more remote - 
from the anode. In other words, they have acquired the 
property of conduction. It is as though the length of the 
anode wire had been extended into the tube. In the lan- 
guage of the two-fluid theory, positive electricity has be- 
