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 
af oetimointhodinootian_of.fiaare a" 
CORRECTIONS. pa¢ a 
ACADEMY OF SCIENCE OF ST. Louis, VoL. XIX. No. 1. 
Page 8, line 12 from top, for Thompson read Thomson. 
fe ‘““ 9 from bottom, for ironization read ionization. 
6 from bottom, for ironized read ionized. 
** 6, bottom line read used. 
6 6é 
to be a ‘‘positive discharge’’ into Lake Erie. 
The positive luminescence in Thomson’s long tube may 
be explained as follows: 
The ixonization 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- 
