1055 
the gasometer from which it is pumped back into high-pressure 
supply-cylinders *). 
The uniformity of the temperature in the experimental space is 
checked by means of two resistance-thermometers 6, and @, (fig.1), 
consisting of platinum wires which are loosely wound on small 
porcelain cylinders with screwshaped grooves and. are provided with 
two pairs of conducting wires’). The axes of the cylinders are 
placed horizontally (see fig. 4) *). 
The regulation of the temperature to a constant value is conducted 
by means of a hydrogen thermometer, the german silver bulb of 
which @, (volume 5,2 ce, see fig. 3) is placed in the regulating and 
adjusting chamber. At the ordinary temperature the larger part of 
the quantity of the gas required is contained in the wide tube of the 
manometer-part Oo (fig. 6) of the thermometer: when the thermo- 
-meter-bulb has been cooled to the low temperature, the gas is 
transferred to it by forcing up the mercury in the manometer. For 
this purpose the open tube @,,, of the manometer is connected with 
the closed part attached to the thermometer by means of an india- 
rubber tube of sufficient length. The mercury is driven up, until it 
lifts a small glass float d (see figs 6 and 7), which is provided with 
a small platinum plate and a platinum contact-wire passing through 
the float and brings it close to a platinum point which is sealed 
into the capillary.®. The fine adjustment can be accomplished by 
means of a micrometer screw u. If. the temperature in the adjusting 
chamber of the cryostat, which we may take to be the same as 
that of the experimental space, falls, the float makes contact with 
the platinum point *), and in this manner switches in a shunt-con- 
1) As the figure shows, two other tubes are connected with e, viz. a leading-off- 
tube from the evaporator with safety tube and a tube connecting the evaporator 
with the gasometer independently of the “spedometer” (see section 3): both these 
tubes are closed by pinching screws lj, /. when the cryostat is in use, they both 
serve in filling the evaporator. ; 
2) So far we have not had an opportunity to exchange the thermometers and 
thus obtain a definite opinion as to the uniformity of the temperature, as in one 
of them a small change of the zero occurred, our statement that a constancy 
down to 0.00° has been reached is also to be taken as a provisional one founded 
on an estimation. 
8) The further apparatus which the experimental chamber will be seen to contain 
in the drawings are a vapour-pressure apparatus, a helium thermometer and a 
resistance thermometer to be examined: these are connected with measurements 
which will form the subject of later communications. 
4) The adjustment at this point corresponds to an initial pressure of about 8 
atmospheres, the thermometer being taken as one of constant volume. 
5) This contact works best, when the small plate is amalgamated and covered 
67* 
