90. Mr. McClung on the Effect of Temperature on the 
the arm Q could always be brought back to the same point 
by adjusting the height of the mercury reservoir S, and the 
gas in the cylinder could thus be kept at a constant volume 

Fig. 4. 
eben 
Oi 
Ww 
pre 
EARTH y | EARTH 
ir i 
Q | 
H 2 | 

i 
EARTH 

ISIN 
BSIQs 
f 
Hef 
: LARTH. 
and density. Measuring the temperature by this method 
obviated the necessity of inserting a mercury thermometer 
into the vessel, and thereby the number of air-tight junctions 
to be made was lessened. 
The manner of taking observations was somewhat similar 
to that already described in the first method. In some cases 
the ionization was measured at the ordinary temperature of 
the room, and then the gas was gradually heated up from 
point to point. In other cases the reverse order was 
followed and the ionization was measured at the highest 
temperature first and the gas then gradually cooled down, 
and measurements taken at the various temperatures. 
