_Gas_, therefore, in our nomenclature, becomes a
generic term, expressing the fullest degree of saturation in any body
with caloric; being, in fact, a term expressive of a mode of existence.
To distinguish each species of gas, we employ a second term from the
name of the base, which, saturated with caloric, forms each particular
gas. Thus, we name water combined to saturation with caloric, so as to
form an elastic fluid, _aqueous gas_; ether, combined in the same
manner, _etherial gas_; the combination of alkohol with caloric, becomes
_alkoholic gas_; and, following the same principles, we have _muriatic
acid gas_, _ammoniacal gas_, and so on of every substance susceptible of
being combined with caloric, in such a manner as to assume the gasseous
or elastic aeriform state.

We have already seen, that the atmospheric air is composed of two
gasses, or aeriform fluids, one of which is capable, by respiration, of
contributing to animal life, and in which metals are calcinable, and
combustible bodies may burn; the other, on the contrary, is endowed with
directly opposite qualities; it cannot be breathed by animals, neither
will it admit of the combustion of inflammable bodies, nor of the
calcination of metals. We have given to the base of the former, or
respirable portion of the air, the name of _oxygen_, from [Greek: oxys]
_acidum_, and [Greek: geinomas], _gignor_; because, in reality, one of
the most general properties of this base is to form acids, by combining
with many different substances. The union of this base with caloric we
term _oxygen gas_, which is the same with what was formerly called
_pure_, or _vital air_. The weight of this gas, at the temperature of
10 deg. (54.50), and under a pressure equal to 28 inches of the barometer,
is half a grain for each cubical inch, or one ounce and a half to each
cubical foot.

The chemical properties of the noxious portion of atmospheric air being
hitherto but little known, we have been satisfied to derive the name of
its base from its known quality of killing such animals as are forced to
breathe it, giving it the name of _azote_, from the Greek privitive
particle [Greek: a] and [Greek: xae], vita; hence the name of the
noxious part of atmospheric air is _azotic gas_; the weight of which, in
the same temperature, and under the same pressure, is 1 oz. 2 gros
and 48 grs. to the cubical foot, or 0.4444 of a grain to the cubical
inch. We cannot deny that this name appears somew