( 441 ) 
into E by means of a funnel. We remove the excess of pentane by 
exhausting once more, so that the mercury at last penetrates into 
the bottom part of C, and KS remains filled with it. 
ABB X is placed in the cryostat, and B t CSE in a thermostat 
U (fig. 3), which is kept at 18° .0. 
The mercury now rises in C; mercury is poured into E, so that, 
when A has assumed the temperature of the cryostat, the mercury 
in E stands a few centimeters above the ground-glass junction. 
If the temperature of the cryostat has remained perfectly con¬ 
stant for an hour (the temperature is determined by means of a 
resistance thermometer), E is removed. The excess of mercury 
in E, is then received in a glass beaker V (fig. 3). If the capillary 
remains quite filled to the top, the vessel E is again placed on 
the ground-glass junction after having been care fully cleaned 
beforehand, and now the temperature of ABB X is slowly raised. 
The mercury that issues at S, is received in E. After some time 
the whole apparatus is placed in the thermostat of 18°.0, and there 
it is left for a considerable time. Now a glass beaker is placed 
under B x CSE, E is carefully removed from the ground-glass junction, 
so that the mercury flows into the beaker, the mercury on the 
surface of the ground junction being collected with a feather. 
The mercury found in the beaker is carefully washed with water, 
then with alcohol. This is removed by means of a current of air 
which has been filtered through cotton wool. The drying is repeated, 
till the weight has become constant. 
b. The Cryostat. 
10. For the measurements at — 38° we used liquid methyl 
chloride under reduced pressure, at —164° liquid methane at 1 atm. 
The apparatus constructed by Kamerlingh Onnes for such purposes *), 
1S ^grammatically represented in fig. 3. AA is an entirely transparent 
vacuum glass, which can contain ± 2 liters of liquid, BB is a brass 
cover, which can be fastened gastiglit on the glass by means of a 
rubber ring. The neck CC can be closed gastight by means of a 
terge rubber stopper. The stopper D was pierced in six places; 
through three holes passed the capillaries E of three dilatometers. 
Moreover the glass vessel AA was provided with a resistance 
thermometer G, a pentane thermometer F, and a glass tube H. The 
last reached to the bottom of the vacuum glass. 
*) These Proc. June 1905; Comm, from the Phys. Lab. at Leyden N°. 94c. 
30 
Proceedings Royal Acad. Amsterdam. Vol. XII. 
