160 
T)R. M. W. TRAVERS, MR. G. SEXTER, AXI) DR. A. .TAQUEROD 
The stem of the main and anxiliaiy thermometers passed through two holes in 
a ru]jl>er stopper, p. Througli one of two holes, pierced at right angles to the tirst, 
passed the stem of the hidh yrhich contained pure hydrogen (pp. 138. 130) and commu¬ 
nicated with a manometer. Tlie capillary tube, x, which was sealed at its lower end, 
communicated with a com})ression apjiaratus containing helium, passed through the 
other liole. Tliis tube was employed in an attempt to li(|uefy helium, which will he 
dealt with latei’. In order to make tlie diagram clearer, the glass walls and stem 
of the thermometer are blacked in, the compression tube is drawn in outline, and the 
tube and bulb for the })ui'e liquid hydrogen is represented by the dotted line. 
The thermometer bulb, &c., was enclosed within a wide glass tube, o, 75 millims. in 
diameter and 400 millims. long. This tube was open at the bottom for the intro¬ 
duction of the vacuum vessel containing the liquid hydrogen, and at the top was 
formed into a neck to fit the rubber stopper, p. Surrounding this tube for a 
considerable part of its lengtli was an annular zinc vessel, open at the top, which 
could be filled with liquid air. Tins vessel was in turn surrounded with natural 
wool enclosed within a jacket of linoleum. The diameter of the linoleum jacket was 
such that it exactly filled the space between the vertical wooden supports to which 
the mam and auxiliary thermometers were fixed (p. 141). The liquid-air jacket was 
not essential to the working of the apparatus, even when the liquid hydrogen in the 
vacuum vessel was boiling under reduced pressure at the extremely low temperature 
of 14° abs. It was thought tliat by using it an economy in the liquid hydrogen 
would be effected, but it is impossible to determine whether this was actually the 
case. Wool was packed into the top of the tube, o, and between the tubes which 
projected downwards through the rubber stopper, to shield off radiation from 
above. 
The vacuum vessel containing the liquid was inserted from the lower and open end 
of the tube, o, so as to surround the thermometer bulb, and Avas kept in place by the 
arrangement shoAvn in the figure. A stoppei', t, made of boxAvood, Avas turned on 
the lathe to fit the open end of the tube, o, and an air-tight junction hetAveen 
the tAvo Avas made lyy means of a rubber .sleeA'e, n. The sleeArn A\ as fixed permanently 
to the stopper, and the upper part of it could be rolled back, and then slipped OA*er 
the tube, o, A\dien the stopper was in position. A brass tube, r, passing through 
the sto])])er, could be connected Avith the exhaust pump by means of a rubber 
connection and lead tube; as the brass tube Avas soldered to a heavy brass plate, w, 
Avhich Avas screAved to the outer sindace of the stopper, it neA’er became cold, and 
a good iunction Avith the rublter tube Avas maintained during the experiment. It 
may be remarked here tliat in carrying out experiments at Ioav temperatures, it 
is impossible to make air-tiglit junctions hetAveen frozen rubber and metal on account 
of the greater contraction of the latter. 
The Anicuum vessel was su])})orted oii foui- Avires, pp let into the Avooden stopper 
and coA^ered at the top Avith pads of cloth. Wire rings Avere soldered to them at 
