54 
PKOFP]SSOB W. RAMSAY AND DR. I\r. 5V. TRAVERS 
Fig. 3. 
amalgamated silver-foil, wliich effectually retained any small globule of mercury which 
miglit have been carried over into the globe E by the stream of gas. The apparatus 
communicated witli the 2 :»ump through the stoj)-cock c. 
The method of manipulation was briefly 
as follows. The apparatus was first filled 
with mercury to the level of the stoji-cocks 
a and 6, which were closed ; the reservoir D 
was then lowered, so as to leave a baro¬ 
metric vacuum in the tubes A and B; the 
stop-cock d was then closed. The globe E 
was now attached to C by a short length 
of thick-walled india-rubber tubing, which 
was wired at both ends; the globe itself 
Avas enclosed in a small cardboard box, 
Avhich also contained the bulb of the thermo¬ 
meter. The stop-cocks a, c, and e Avere noAv 
turned, so as to place the Avhole of the 
apparatus in communication AAuth the jAump. 
It Avas pai'ticidaily important to remoA'e 
the air in the bore of the stop-cock a, as its 
volume Avas not inconsiderable in com- 
2)arison Avith that of the gas Aveighed, 
After exhausting the apparatus, the stop¬ 
cock a AAns closed, and bv turning the 
sto])-cock d, the mercury Avas alloAved to rise 
in the burette. The gas Avas then intro¬ 
duced through the siphon into the burette, 
and the stop-cock c Avas closed. On turn¬ 
ing the stop-cock o, the gas entered the 
globe, while the resei’A’oir D aa'us held in 
such a position that the mercury did not 
rise above a. The stoj)-cock 6 AAns then 
opened, the stop-cock a being momentarily 
closed, in order to aAmid any danger of 
mercury being forced up into C ; and the 
^Aosition of the reseiwoir D Avas adjusted, so that the surface of the mercury in A lay 
as near as possil)le to the top of the tul)e. After about a cpiarter of an hour, the 
temperature and pressure Avere observed, the stop-cock e AAns closed, and the barometer 
Avas read. The gas contained in the tube C and in the burette Avas remoAnd by 
exhaustion, and collected through the pump, and the globe Avas detached from the 
apparatus and suspended in the balance. 
