Mr. Schmeisser's Description of an Instrument, &c. 165 
preferable to, those which have been hitherto made public ; 
and even to that lately invented and recommended by Mr. 
Rams den. 
The whole apparatus is represented in Tab. XIX. fig. 1 ; it 
consists of a flat-bottomed glass bottle (fig. 2) in which is 
fitted, by grinding, a glass stopper having a thermometer 
passing through it, (fig. 3.) The bore of this stopper is coni- 
cal, (fig. 4) and the thermometer has a glass collar, (fig. 5) 
which is ground into the bore of the stopper, so as to be per- 
fectly tight. There is some difficulty both in making the glass 
collar, and in fitting it into the stopper. If the thermometer 
tube and the collar be not made of the same metal, the collar 
is very apt to fly off in grinding ; for this reason I have some- 
times fixed the tube into the stopper by means of a thin piece 
of elastic gum, wound very tight round the tube. This gum, 
by its elasticity, effectually excludes air and liquids, and is, in 
the usual temperature of the atmosphere, not dissolved by 
any liquor, except vitriolic aether, and not even by that, un- 
less it is particularly prepared for the purpose. 
The cavity left at the upper part of the stopper may be 
filled up with sealing w r ax, or any other kind of cement ; this 
will assist in fixing the tube, and as the liquors to be weighed 
do not come in contact with this part, if the bottle be care- 
fully filled, there is no danger that the wax, or cement made 
use of, should in any degree affect the accuracy of the ex- 
periments. 
I have made, at different times, comparative experiments 
with this instrument, with a view to the further ascertaining 
its accuracy, and the different improvements made in it ; 
and I can with much confidence assert, that I have never 
MDCCXCII I. Z 
