86 ROYAL SOCIETY OF CANADA 
It is well known that these rays impress electrical conductivity upon 
gases which they traverse, and it is generally agreed that they consist 
of very small negatively charged particles of matter. Their presence 
within the cylinders would therefore account for the observed conduc- 
tivity, and for the negative charges gained by the electrode at low 
pressures. 
But there are difficulties connected with the supposed production 
of cathode rays within the cylinders which are not easily explained. 
That these rays travelled from the cathode of the discharge tube through 
the thick brass walls to the electrode C, Professor Thomson considered 
highly improbable. He suggested, however, that possibly the effects 
may have been due to secondary discharges between the cylinder and the 
inclosed electrode; that, in fact, the ends of the cylinders, when under 
bombardment by the cathode rays of the discharge tube, may have be- 
come negatively charged, and acting as new cathodes may have pro- 
jected streams of cathode rays against the electrode. 
As an objection to this explanation it may be pointed out that 
when the discharge tubes were excited, the cylinders were always con- 
nected to earth by wires of small resistance. It therefore seems pro- 
bable that if portions of cylinders acquired potentials sufficiently high 
to produce discharges of cathode rays, these discharges would also have 
been accompanied by electric curfents of considerable intensity along 
the earth wires. There appears, however, to be no indication that such 
currents existed, and in default of further experimental evidence the 
hypothesis of secondary discharges seems hardly tenable. 
The object of the experiments described in this paper was to in- 
vestigate this point more fully and to determine, if possible, a more 
satisfactory explanation of the effect. 
The investigation was begun with tubes identical in construction 
with those used by Professor Thomson, but as these could not be taken 
apart to make changes in the cylinders the experiments were com- 
pleted with tubes somewhat modified in form. 
The experiments are described under the following subdivisions :— 
1. Preliminary experiments. 
2. Electrical conduction along the surface of glass. 
3. Penetrating power of cathode rays. 
4. Influence of bad earth connections. 
5. Influence of small openings in Faraday cylinders inserted in 
vacuum tubes. 
