Defeription of a Mercurial Gazometer. 155 
poflible to japan tin or copper fo perfectly as to prevent their 
being attacked by mercury when brought in contaét with 
them, I had the cylinders turned in hignum vite, on which 
the mercury has no action: the conduéting tube is of glafs 3 
and the cocks aré coated on the infide with varnith. 
The ufefulnefs of an apparatus fo conf{tracted will appear 
fufficiently obvious, when it is recollected that all gafes pafled 
through any other fluid than mereury, watef for inftance, 
take up a quantity of moifture, which adds confiderably to 
their gravity, and makes it impoffible to determine their 
x. real weight. 
' 
- For Pp Pighing of gafes I make ufe of a glafs globe and ftop- 
eock of a fasaller fize than is commonly employed, as greater 
accuracy can be obtained by ufing a proportionally delicate 
beam than by employing a larger globe, which muft be fuf- 
pended to a beam of fuch Giese as greatly to inereafe the 
' friction on its axes. Itis of great importance, in the analyfis 
of bodies, or in other chemical experiments, to be able to 
afcertain with accuracy the weight of any gas obtained by 
the procefs. The weight of two or more quantities of gas 
fhould however be always tried; and the mean be taken to 
prevent any error. 
A, (Plate IIT.) is a reprefentation of the bell of the gazo- 
meter, made of glafs, furnifhed with a cock at top, ach able 
to contain 34 ounces troy of diftilled water. The divifions 
Of capacity, determined by actual meafurement, are marked 
on the glafs with a diamond. BB, fection of two cylinders 
of lignum vite, the outward one {crewed upon the folid in- 
ternal one, which is made to project at its lower extremity, 
and furnifhed with a male fcrew; to work into a female ferew 
with which the lower end of the external cylinder is fur 
nifhed. The fpace between thefe is fo adjufted as to be al- 
moftt filled up by the fubftance of the glafs bell A when 
dropped into it, fo that the quantity of mercury neceflary-to 
fill up that fpace is proportionally fmall. The internal cy- 
linder has a conducting tube up through its axis, the lower 
end of which is furnifhed with a female ferew anfwering to 
the male fcrew of the cock of the {mall receiver C. The re- 
eeiver C is made of glafs, and open at bottom, When this 
tn X 2 receiver 
