Radiation from Gases subject to X-Rays. 687 



direction perpendicular to the two ends, and from which it 

 was separated by an ebonite plug P. Connexion could be 

 made between this rod and the insulated plate and gold-leaf 

 by means of a light spring K which was attached to the rod, 

 and which when set in vibration made contact with the 

 insulated portion of the electroscope. The capacity of this 

 was exceedingly small in the Inter experiments, the brass 

 plate being replaced by a straight piece of copper wire to 

 which was attached a narrow strip of gold-leaf. The deflexion 

 of the gold-leaf was observed through a microscope with 

 graduated eyepiece, which was fixed just outside a small 

 glass window M in one side of the case. 



When the rod was connected to one terminal of a battery, 

 while the other terminal was earth-connected, the insulated 

 plate and gold-leaf could be charged by means of the Contact- 

 maker, which made momentary connexion between the rod 

 and plate, leaving the plate and gold-leaf charged and 

 insulated. 



When this was the case, a leak of electricity from the plate 

 and gold-leaf was only possible by the sulphur support or 

 through the air in the electroscope. It was shown that the 

 leak by the support was negligible by first discharging the 

 electroscope completely, and then charging the cylindrical 

 supporting rod to a high potential, by connecting to one 

 terminal of a battery the other terminal of which was earthed, 

 and then leaving the apparatus for a number of hours. The 

 amount by which the leaf and plate charged was (the amount 

 of leak through the support) — (the amount of leak through the 

 air). The latter was very small, as the potential of the plate 

 and gold-leaf was little different from that of the case, which 

 was earth-connected. There was no perceptible change in 

 the position of the gold-leaf. 



When the rod was kept at a higher potential than the 

 insulated portion, and this again was at a considerably higher 

 potential than the earthed case, the leak through the gas was 

 not negligible, and the amount by which the leaf and plate 

 charged was 



(amount of leak through tin 1 support) — (amount of leak 



through the air)=«. 

 When, on the other hand, the leaf and plate 4 were charged to a 

 higher potential than the supporting rod the loss of charge by 

 the former was 



(amount of leak through the support) + (amount of leak 



through the air)=/3. 

 When the potential of the leaf and plate was the same in each 



