ly exhaled may be one cause of
the luxuriancy of plants growing on dunghills or in very rich soils.

P. 146. Your observation that inflammable air consists of the union of
some acid vapour with phlogiston, puts me in mind of an old observation
of Dr. Cullen, that the oil separated from soap by an acid was much more
inflammable than before, resembling essential oil, and soluble in V. sp.

I have tried fixed air as an antiseptic taken in by respiration, but
with no great success. In one case it seemed to be of service, in two it
seemed indifferent, and in one was injurious, by exciting a cough.

NUMBER V.

_Extract of a Letter from Mr. WILLIAM BEWLEY, of GREAT MASSINGHAM,
NORFOLK._

March 23, 1774.

Dear Sir,

When I first received your paper, I happened to have a process going on
for the preparation of _nitrous ether_, without distillation.[25] I had
heretofore always taken for granted that the elastic fluid generated in
that preparation was _fixed_ air: but on examination I found this
combination of the nitrous acid with inflammable spirits, produced an
elastic fluid that had the same general properties with the air that you
unwillingly, though very properly, in my opinion, term _nitrous_; as I
believe it is not to be procured without employing the _nitrous_ acid,
either in a simple state, or compounded, as in _aqua regia_. I shall
suggest, however, by and by some doubts with respect to it's title to
the appellation of _air_.

Water impregnated with your nitrous air _certainly_, as you suspected
from it's taste, contains the nitrous acid. On saturating a quantity of
this water with a fixed alcali, and then evaporating, &c. I have
procured two chrystals of nitre. But the principal observations that
have occurred to me on the subject of nitrous air are the following. My
experiments have been few and made by snatches, under every disadvantage
as to apparatus, &c. and with frequent interruptions; and yet I think
they are to be depended upon.

My first remark is, that nitrous air does not give water a sensibly acid
impregnation, unless it comes into contact, or is mixed with a portion
of common or atmospherical air: and my second, that nitrous air
principally consists of the nitrous acid itself, reduced to the state of
a _permanent_ vapour not condensable by cold, like other vapours, but
which requires the presence and admixture of common air to restore it to
its primit