70 Prof. J. A. McClelland on the 
Second Experiment. 
The experiment described above is not conclusive Fe ie 
whether the y rays carry an electric charge because 0 ae 
effect due to the surrounding ionized gas. This effect cou : 
of course be largely eliminated by carrying out the exper ar 
inahigh vacuum. It was more convenient, however, to modily 
the apparatus in another way (fie. s 1). 
Fig. 1. 
o 
N 
YY 
= 
S 
s 
G 
Si 
\ 
LZARTH 
A tin cylinder 6, 20 ems. long and 8 cms. diameter, was 
placed inside a second tin cylinder a, 25°5 cms. long and 10 ems. 
diameter, and the annular space between flooded with liquid 
paraffin, which solidified, insulating the inner cylinder from 
the outer, which was to earth. The inner cylinder was filled 
with shot so that it absorbed a pencil of y rays passed 
along it. The 50 milligrams of radium bromide producing 
the y rays were contained in a small vessel R placed in a hole 
in a block of lead, so as to limit its radiation to a diverging 
pencil with its axis parallel to the axis of the shot-cylinder, 
and thus prevent the rays from falling on other parts of the 
apparatus. | 
A wire from the inner cylinder leads to the electrometer 
placed some yards away, the wire being led along the axis 
of an earthed. metal tube filled with paraffin. The inner 
cylinder and the wire leading from it were thus not exposed 
to air ionized by the radium. | 
The vessel a was thick enough to stop all the « rays; the 
