190 Mr Almy, On a Diminution of the Potential Difference, etc. 
Table VII. Potential difference between the electrodes. 
Wire as cathode 
Wire as anode 
Without magnet 
7400 
8400 
Magnet parallel to tube 
2800 
<400 
Magnet normal to tube 
3000 
<400 
1 
that of concentrating the discharge, so that the discharge through 
the gas takes place by a sort of brush — or arc — discharge, in fact 
with some similarity to disruptive discharge, instead of as usual 
in the Crookes’ tube discharge. And the effect of this concen- 
tration is to very greatly increase the conductivity, or diminish 
the resistance to discharge, of the tube. 
In conclusion, I wish to express my thanks to Professor 
J. J. Thomson for the many privileges afforded at the Cavendish 
Laboratory, and for his advice and help given in the course of 
this work. 
