Mr Alrny , On a Diminution of the Potential Difference, etc. 189 
Table VI. Potential difference between the electrodes. 
Without 
magnet 
1 
Magnet 
transverse 
Magnet 
parallel 
With cathode a 
2200 
1550 
1500 
With cathode b 
5000 
3900 
3600 
a surrounded with tinfoil 
1600 
1550 
1550 
1 b surrounded with tinfoil 
4000 
4000 
4000 
the effects produced have magnitudes in the ratio 6 : 10 while 
the distance between the walls of the tube varies as 1 : 4. 
As this experiment is hardly to be re- 
garded as conclusive a tube of the form 
shown in Fig. 3 was tried. One electrode, 
a thick aluminium wire, partly enclosed by 
a thick-walled glass tube was inside the 
other electrode, a cylinder, with end closed 
by a disc of metal next the glass tube ; by 
this form of electrodes the inner was shielded 
from the action of a static charge on the 
glass. 
With this tube the magnetic diminution 
was produced, and, with the wire as cathode 
the effect produced is of remarkable mag- 
nitude, in some cases ; namely at times the 
discharge reduces to a small luminous brush 
or bundle of lines, passing from the wire to 
the cylinder, resembling the arc discharge 
at atmospheric pressure. (Table VII.) 
The potential differences in the two 
cases indicated as < 400 was much smaller 
than that necessary to give a single division 
deflection of the voltmeter; its actual mag- 
nitude was not obtained. 
These results seem to show conclusively that the action of the 
magnetic field is independent of any static charge on the walls of 
the discharge-tube, since it is produced when the cathode is prac- 
tically surrounded by the other electrode. 
In short, the action of the magnetic field seems to be simply 
