1052 
evaporator in the manner commonly used in the laboratory (Comm. 
N°. 94/, Proc. 1X p. 156 comp. also PL. 1 Comm. N°. 103 Proc. X p. 592) 
from a supply-bulb through the tube a,, which is closed by a small 
rubber tube with glass stopper. In the beginning the evaporator is 
filled up to X,; when the liquid surface has sunk to X, a fresh 
supply is put in. Through the copper tube 5, gaseous hydrogen is 
led in from a high-pressure supply cylinder; this gas undergoes a 
preliminary cooling in 6, and is then carried into the liquid hydrogen 
by the tube 6, (which is made of german silver in order to reduce 
heat-conduction to the liquid hydrogen) and the copper tube b,; this 
causes a continuous evolution of hydrogen vapour, which is carried 
to the eryostat-glass 5, — a silvered vacuum glass — by the glass 
tube C,. On its way it passes the glass spiral C, and the syphon- 
like twice bent silvered vaeuum-tube C,, C, C, which is sealed to C,. 
Its end-piece C, is sealed into the supply-tube Za, of the heating- 
chamber Ea, which is the lower one of two adjoining flat horizontal 
copper boxes, the upper one Ea, serving as regulating and adjusting 
chamber, the two together being attached to the hollow bottom of 
the experimental chamber. The two boxes are isolated from each 
other and similarly the upper one from the bottom of the experi- 
mental chamber by means of paper; inside each of the boxes is 
provided with a vertical partition running round as a spiral Za, 
Ea,, by which they are made into spirally wound tubes of rectan- 
gular section. Inside the spiral of the heating box is a heating wire 
of constantan of 100 £, insulated with silk. and wound round a 
flat spirally wound band (the wire is shown diagrammatically in 
fig.6 as Ea,,). After passing through the heating tube the superheated 
hydrogen-vapour, which is now brought to the desired temperature, 
flows into the regulating and adjusting chamber £a;, where it follows 
again the spiralshaped path shown it by the partition Za,,. In doing 
so it passes along a tin wire insulated with silk and arranged as 
Ea,, the resistance of which is measured to 0.001 on a commercial 
Wueatstone-bridge. According to the indication of the resistance of 
this wire the temperature is approximately adjusted. The same 
adjusting chamber also contains the bulb of the regulating thermo- 
meter @, (see fig. 3), which will be discussed further down. 
After having passed the adjusting and regulating chamber at the 
bottom of the experimental chamber, the gas passes (zie figs. 3, 4, 5) 
a copper exchange tube £b, which consists of eight tubes alternately 
running up (£6,) and down (£6,) coupled by horizontal chambers 
(Eb,), the whole being intimately united *) with the vessel which is 
1) The tubes are soldered to the side-wall of the experimental chamber, the 
