1053 
~ 
formed by the side-wall £b, and the bottom of the experimental 
chamber and is of high conductivity and comparatively large heat- 
capacity (the vessel with its lid weighs 1.2 k.g.) Finally the gas 
emerges in the experimental space immediately above the bottom at 
Eb,, and finds its way to the protecting space in the eryostat-glass 
above the experimental chamber through small apertures‘) in the 
copper lid Ze (fig. 1), which closes the experimental chamber at 
the top. 
The copper vessel 4b with its lid He which encloses the experi- 
mental space, together with the box attached to the bottom, occupies 
the lower part of the eryostat-vessel (see fig. 1), and hangs, without 
touching the inner wall of this vessel, by means of the vacuum- 
tube C, and the glass rod Hd from the air-tight cap By, which 
closes the vacuum-vessel B, in the manner commonly used in the 
laboratory (see previous Communications of this series). Supply of 
heat by conduction to the walls of the experimental space is therefore 
practically excluded *). 
Besides the measuring-apparatus, the necessary electric wires and 
the supply-tube of the superheated hydrogen-vapour C,, the cap of 
the cryostat-vessel By (see fig. 1) transmits air-tight a second doubly 
bent syphon-like silvered vacuum-tube d,d,d,, through which the 
hydrogen flows back to the evaporator. Here it passes through the 
regenerator Vr, which serves to effect a preliminary cooling of the 
hydrogen of ordinary temperature by which the evaporator is fed *) ; 
ultimately (see fig.6) by way of e and a tap A, it finds its way to 
wall being shaped for the tubes to fit it as nearly as possible. Moreover the con- 
duction between tubes and wall is promoted by a thick filling of solder. 
1) The lid closes the experimental chamber as nearly as possible, but is not 
made air-tight. The side-wall Eb, (see fig. 1) is provided at the top with a 
horizontal ring-shaped rim Ec, which is soldered to it. On to this rim a number 
of small copper covering-plates are screwed, 2 mm. thick and fitting the rim, of 
such profiles, that when the measuring apparatus are in their proper places the 
plates cover up the experimental chamber as completely as possible and complete 
the lid until only a few interstices and small holes remain, through which gas 
may escape while at the same time the measuring apparatus in the experimental 
space are protected from radiation. 
2) In order to prevent a radiation from the cap to the lid of the experimental 
chamber, screens Ef (shown as dotted lines in fig. 1) can be fitted in the pro- 
tecting space, which are cooled down by the gas which emerges from theexperi- 
mental space. : 
8) The dimensions of the apparatus do not admit of more than a moderate 
degree of regeneration, as the tube bz cannot be very narrow in connection with 
a proper regulation of the supply. 
67 
Proceedings Royal Acad. Amsterdam, Vol. XIX. 
