IV.

OF THE AREOMETER, OR PROOF BOTTLE.

This instrument is indispensable to the distiller: it ascertains the
value of his spirits, since it shows the result of their different
degrees of concentration. I will give the theory of this useful
instrument, as it may be acceptable to those who do not know it.

Bodies sink in fluids, in a _compound ratio_ to the volume and the
density of those fluids, which they displace. It is from that law of
nature, that a ship sinks 20 feet in fresh water, while it sinks only
about 18 feet in sea water, which has more density on account of the
salt dissolved therein.

The reverse of this effect takes place in fluids lighter than water, as
bodies floating in them sink the more, as the liquor has less density.
Upon those principles are made two kinds of areometers--one for fluids
denser than water; the other for those that are lighter: the first are
called _salt proof_; the second _spirit proof_. Distilled water is the
basis of those two scales: it is at the top for the _salt proof_, and at
the bottom for the _spirit proof_; because the first is ascending, and
the other descending; but by a useless singularity, the distilled water
has been graduated at 10 deg. for the spirit proof bottle, and at 0 for the
_salt proof_. We shall only dwell upon the first, because it is the only
one interesting to the distiller.

Water being graduated at 10 deg. in the areometer, it results from thence
that the spirit going to 20 deg., is in reality only 10 deg. lighter than water;
and the alcohol gaaduated [TR: graduated] at 35 deg., is only 25 deg. above
distilled water.

The areometer can only be just, when the atmosphere is temperate; that
is, at 55 deg. Fahrenheit, or 10 deg. Reaumur. The variations in cold or heat
influence liquors; they acquire density in the cold, and lose it in the
heat: hence follows that the areometer does not sink enough in the
winter, and sinks too much in the summer.

Naturalists have observed that variation, and regulated it. They have
ascertained that 1 deg. of heat above temperate, according to the scale of
Reaumur, sinks the areometer 1/8 of a degree more; and that 1 deg. less of
heat, had the contrary effect: thus the heat being at 18 deg. of Reaumur,
the spirit marking 21 deg. by the areometer, is really only at 20 deg.. The cold
being at 8 deg. below temperate, the spirit marking only 19 deg. by the
areometer, is in reality at 20 deg.. 2-1/4 of Fahrenheit corresp