upon a Table, will
burn perhaps a Minute or two in Proportion to the Quantity of Air pent up
with the Candle in the Bell; but as soon as the Quality in that Air, which
is necessary to feed the Flame, is exhausted, the Candle goes out; this
has been often try'd with the same Success; and we find, that by letting
into the Bell some fresh Air, a little before the Candle should have gone
out, it will still continue burning: And then to shew that this Quality in
the Air is the same which feeds the Life in Humane Bodies, it was try'd,
whether the Air, returning from the Lungs, would not have the same Effect
upon the Candle, as the External Air had before, but it had not, the
Candle went out at its usual Time: Thus, it seems, when we suck in Air for
Breath, the Lungs takes what is necessary for the Nourishment of our
Bodies, and returns back the rest.

After this we may naturally conclude, that where the Rooms, or Houses are
small, there ought to be frequent Admissions of the External Air, but
especially where those Rooms or Houses are too much crouded with People;
and if it is supposed that the External Air is Infectious, the burning of
_Aromaticks_, _Gums_, or _Herbs_, upon the letting in of fresh Air, is
necessary.

From the foregoing Observations we may learn, that all Pestilential
Distempers, whether in Animals or Plants, are occasion'd by poisonous
Insects convey'd from Place to Place by the Air, and that by uncleanly
Living and poor Diet, Humane and other Bodies are disposed to receive such
_Insects_ into the Stomach and most noble Parts; while, on the other Hand,
such Bodies as are in full Strength, and are well guarded with
Aromaticks, would resist and drive them away, but chiefly how necessary it
is to allow the Body a Freedom of Air, and how to correct it if it is
Infected.

And I shall conclude with some Memorandums taken from the Papers of a
learned Gentleman, who in the time of the late Plague in _London_ was
curious enough to make his Remarks upon the Signs of that Distemper, and
the Method of its Cure.

He tells, the Plague proceeds first from a corrupted and unwholsome Air.

The Second, is putrified Humours, hot Blood, caused by breathing in such
corrupt Air; and if the Diet before were perverse, it fills the Body with
superfluous Humours.

Concerning the common Fear of Infection, which makes many rich Men, which
might and ought to maintain poor visited People; and some Physicians
likewise, whose Duty i