( 1095 ) 
In the lower part — the cryostat space — of the glass 4’, (Fig. 
1 and Fig. 2) is the reservoir 7%' of the helium thermometer, with 
which the temperature of the bath is determined, the resistance 2, 
the dilatometer A, and the control apparatus of the dilatometer d. 
And finally, a thick copper rod Cu is also placed in it so that, 
since the liquid in the bath cannot be stirred, conduction along the 
rod may keep the temperature of the bath more equable at all points. 
The narrow space between the regenerator spiral A and the wall 
of the vacuum glass /”, is filled with flannel, and now three capil- 
laries pass through it instead of the single thermometer capillary 
(that of 7A, Pl. HI Comm. N° 108). One of these, 77/’',, leads io 
the thermometer (replacing 7h,, Th, Zh, Th,, of Pl. HI, Comm. 
N°. 108), the second to the dilatometer (this was already used in 
Comm. N°. 112), and the third to the control apparatus of the dila- 
tometer (connecting JS with JI’). Furthermore, instead of the two 
insulated wires of the thermocouple (Comm. N°. 108) four insulated 
wires Wa, Wa,, WA, Wo,, now pass through this space; these 
are the pairs of wires that lead the current to and from the resi- 
stance 2. 
All these capillaries and insulated wires must pass through the 
space that is filled with liquid air, which must still remain airtight 
(this space is deseribed under Jd of Comm. N°. 108 § 2, and 5 PI. II 
of that Comm. shows how liquid air is introduced). This is accom- 
plished by soldering the capillaries to the new-silver wall of the 
liquid air vessel, while the insulated leads are enclosed in new-silver 
tubes that pass through the wall and are soldered to it. 
The operation of filling the lower portion /,, (Pl. I fig. 1) with 
liquid helium is conducted in exactly the same way as is described 
in § 4 Comm. N. 108. Practice in the various operations and the 
improvement made by introducing the second helium thermometer 
rendered it possible to save a fair amount of liquid hydrogen so 
that, as a part of the necessary hydrogen had been liquefied the 
previous day, it was possible to begin at half past seven in the 
morning and have the cryostat part of the apparatus full of 
liquid helium by a quarter to two in the afternoon. The circulation 
pressure was kept at 25 atmospheres (cf. § 2, Comm. N°. 112). 
The pressure under which the helium vaporizes is derived from 
the pressure obtaining in the wide space beneath the german silver 
chamber /’; from this space a tube passes through / and comes 
outside the apparatus at p,; it is there coupled to the apparatus for 
regulating and measuring the pressure. The difference of pressure 
between this space and the surface of the liquid helium necessary 
