300) > Mr, Ky McClung on the Relative Amount of 
was that it is a much more sensitive and exact one than that 
of comparing separate and direct measurements made on the 
two gases at different times. 
Description of Apparatus and Method. 
ee ee a a 
The apparatus which was used is shown diagrammatically 
in fig. 1. The Réntgen-ray bulb was enclosed as usual in a 
Fig. 1, 
a 
ri ee. 
si 
LARTH 
EARTH 
a 
C7, 
Cc’ 
EARTH 
lead-covered box and the rays emerged through a rectangular 
opening A. BB’ and CC’ were two brass cylinders which 
contained the gases which were ionized. These cylinders 
were about 27 cms. in length and 8 cms. in diameter. The 
ends at Band C were made of thick aluminium plates re- 
cessed at the centre, as shown in the diagram, so that the 
rays might only haye to pass through a small thickness of 
