On Cathode and Canal Rays. 181 
part of it which is used up in producing the rays falling on 
AE is diverted when the collecting electrode is connected 
to earth. The decrease of current must therefore be pro- 
portional to. the quantity of diverted cathode or canal rays. 
This inference was confirmed by the experiments, and fur- 
nished me with a second though difficult check method, for 
determining the relation of the conveciion-currents repre- 
sented by the cathode and canal rays to the exciting current. 
Thereby I was put in possession of two mutually independent 
modes of investigation. 
Description of Apparatus. 
Altogether five different forms of discharge-tube were used. 
Here I shall, however, describe only two of the most im- 
portant. For one series of experiments I used the tube 
shown in fig. 1. This was quite symmetrical with respect to 
both electrodes. These latter consisted of two exactly equal 
brass tubes 3 cms. long, with a piece of gauze, forming a 
“net” electrode, soldered to each. The distance between 
the pieces of gauze was 6°5 cms. The three component glass 
portions of the tube fitted tightly into the brass tubes just 
mentioned, and were cemented to them by means of sealing- 
wax. The collecting electrode AE was provided with the 
following arrangement for displacing it without altering the 
vacuum. The collector was attached by means of two thick 
copper wires to a nut which moved between two guides, the 
latter being soldered to a springy ring of brass which pressed 
tightly against the glass walls of the tube. By means of a 
long screw passing through the nut and cemented to an 
easily rotating stopper, the electrode could be displaced to 
and fro by simply turning the stopper. 
The experiments with other gases required a different form 
of tube, in which all bodies capable of giving off gases, such 
as greased stoppers, cemented joints, &c. had to be avoided. 
For this reason in such experiments the tube shown in fig. 2 
was mostly used. It consisted of a glass tube about 35 cms. 
long and having an internal diameter of 3°2 cms. lt was 
used in a vertical position, the upper end being closed and 
the lower one continued into a barometer-tube. The two 
perfectly symmetrical net-electrodes consisted of ‘nets of 
the second kind.” It should be explained that in order to 
determine the effect of different nets, two kinds were used. 
The small-meshed nets, or nets of the first kind, were such 
that their wires covered 64°67 per cent. of the total area ; the 
openings were square. In the wide-meshed nets, or nets of 
the second kind, the wires covered 48°37 per cent. of the 
