306 
while, as was already remarked, the temperature jump assumed to 
take place at the surface of the liquid has no influence upon the 
result. We also find 
m — 0,017, v, =110, v, = 1035. 
The line drawn in fig. 1 has been calculated from these data. 
The observed pressures, indicated by circles, agree well with the 
results of calculation. 
Between half-past four and five more liquid gas was admitted into 
the eryostat. The readings during which the resulting pressure inter- 
change was stopped by means of a valve are not marked in the 
figure. A slight temperature fluctuation occasioned by the refilling 
is clearly seen in the diagram. A small pressure increase at 5hóm 
dies down about six o’clock quite in accordance with the calculated 
curve. (See 3'27™. At this point the temperature also increased). 
As can be seen, it took more than an hour for the last 1.8 m.m. 
pressure difference to die down to 0.02 m.m. (the whole pressure 
was 9 CM.). 
The calculations show that the assumed distribution of temperature 
along the capillary is, in the main, correct. It gives a very welcome 
estimate of the time requisite for the last appreciable interchange 
of gas. 
To establish pressure equilibrium as rapidly as possible in such 
experiments it is necessary that: 
1. as little of the capillary as possible should project above the 
cryostat, and that the stem within the cryostat should be kept as 
cold as possible; 
2. the upper part of the capillary should be wider than the lower, 
as is the case, for instance, in the helium thermometer of KAMERLINGH 
Onnes, or better still, the connecting capillary should be gradually 
narrowed. (In fig. 5 Comm. Suppl. N°. 216 *) compare the tube which, in 
the experiments by KaAMERLINGH ONNES on the attainment of the lowest 
possible temperatures, had to carry off helium vaporised under a 
pressure of 0.2 mm. with the least possible reduction of pressure; 
the dimensions of this tube were calculated according to the principles 
of $ 2). 
(To be continued). 
1) Bericht über den II. Internationalen Kältekongres, Wien, October 1910, Bd. II. 
