322 Mr. R. T. Beatty on the Production of Cathode 



Parchment was found not to be air-tight, and after some 

 trials the method of treating it which gave most satisfaction 

 was to plunge it in boiling paraffin wax, and then remove 

 the excess of wax between filter-papers. This treatment 

 increased the weight of the paper to that of '01 mm. of Al, 

 but still its absorption of even the Fe radiation was quite 

 small. The parts shown in fig. 3 were assembled by heating 

 BB and CC, covering them with a layer of" beeswax and 

 resin, placing the parchment in position and pressing CG 

 tightly on BB. When the joint was made in this manner 

 no trouble with leakages of air ever arose in this part of the 

 apparatus. 



A brass ring RR was placed above the gauze, as shown in 

 fig. 2, and the opening in it was covered with a parchment 

 sheet tightly gummed on. Above this came the electrode E, 

 a thick brass disk which could be raised or lowered by three 

 vertical screws passing through ebonite plugs in the disk. 

 The points of these screws rested on three small ebonite 

 blocks which fitted in recesses in RR (see fig. 2) and a 

 conical depression at the centre of each block ensured that 

 E could always be replaced in exactly the same position. 

 A wire was led from E to the secondary electroscope, and 

 as the vessel was put at a high potential a guard ring- 

 was used. 



As the vessel had to be opened many times during the 

 course of the experiment, it was necessary to have a lid 

 which could be rapidly and efficiently sealed on or removed. 

 The usual method of soldering seemed unattractive, and, 

 instead, a brass casting AA was screwed on the outside of 

 the vessel, forming a deep channel into which melted wax 

 could be poured. The lid was then placed in position so 

 that the rim fitted into this channel, and a blowpipe flame 

 raised the lid to such a temperature (about 100° C.) that 

 the wax became fluid. On cooling, the joint became quite 

 air-tight. 



The whole vessel was placed above a circular opening in 

 a thick lead plate LL, and insulated from the lead by ebonite 

 blocks. 



The internal arrangements of the vessel were adjusted as 

 follows. A silver leaf was attached to the upper surface of 

 RR while the parchment covering of the latter was moist. 

 The parchment on drying shrank and formed a perfectly 

 plane surface with the leaf adhering to it everywhere. E was 

 then placed on RR and the screws adjusted till the two were 

 parallel. A microscope was used to determine the distance 

 between these surfaces with a possible error of - 02 mm. 



