156 Defcription of a Mercurial Gazometer. 
receiver is ufed, it is ferewed into its place, and refts upon a 
fmal] cup or ciftern of mercury D, in which the beak of a 
retort, furnifhed with a bent glafs tube, to be afterwards no- 
ticed, may be introduced under the receiver, E,E,E,E, fec-' 
tion of a wooden ftand upon which the cylinders of lignum: 
vite are fupported, having an openmg through the top to. 
permut the cock of the receiver C to be joined to the con- 
du@ting tube of the internal cylinder B. The ciftern D is 
adjufted to its height by means of a rifing cylinder in the 
pedeftal F. Gis a transfer glafs for mixing alkaline gafes in 
vacuo, or other purpofes; and, when ufed, is joined to the: 
top of the bell A. H,-a glafs globe and ftop-cock, capable 
of holding 14 ounces troy of diftilled water for weighing 
gafes: it receives its gas by being inverted, and fcrewed inte 
the bell A. I, a bladder furnifhed with a ftop-cock to affitt 
in holding, transferring, or mixing different gafes. K, an 
elaftic gum-bottle, capable of containing 30 ounces of di- — 
filled water, for holding the acid gafes: when ufed, it is 
{crewed into the top of the transfer G; the bottom cock of 
the latter being at the fame time joined to the bell A, previ- 
oufly charged with the alkaline gas: the cocks being turned, 
“the gafes ruth tagether in vacuo. L, a fmall portable air- 
pump, for exhautting the globe H. M,a double male fcrew, 
which fits any part of the apparatus, and on which a valve 
may be faftened. N, a double female ferew. O, a fmall in- 
ftrument, which [ would not have mentioned, had I not found 
it of peculiar fervice in collecting fpilled mercury : it is made 
of glafs, the mouth being applied at @: you may colle&t any 
{mall globules of mercury by the fmall end 4, by which 
means they are elevated into the receiver at Q. It is ufeful 
likewife for removing mercury from the {mall ciftern. 
One of the principal objections to the ufe of mercury im 
fuch experiments as this apparatus is mtended for, has been,. 
the great foree neceflary to overcome the refiftance of a co- 
lumn of mereury when gafes are to be received over that 
denfe fluid; a-refiftance in the proportion of one inch of 
mercury to fourteen inches of water, and which very few 
lutes are able to withftand. «This refiftance I overcome by 
a very fimple contrivance: a bent tube fitted into the beak 
of RY 
