h
as _Malignant Influences of the Heavens_; _Arsenical_, _Bituminous_, or
other _Mineral Effluvia_, with the like imaginary or uncertain Agents.

THIS however I do not say with design absolutely to exclude all
Disorders in the _Air_, that are more latent than the intemperate _Heat_
and _Moisture_ before mentioned, from a Share in increasing and
promoting the Infection of the _Plague_, where it is once bred: for I
rather think this must sometimes be the Case; like to what is observed
among us in relation to another infectious Distemper, namely, the
_Small-Pox_, which is most commonly spread, and propagated by the same
manifest Qualities of the _Air_ as those here described: Notwithstanding
which, this Distemper is sometimes known to rage with great Violence in
the very opposite Constitution of _Air_, _viz._ in the Winter during dry
and frosty Weather. But to breed a Distemper, and to give force to it
when bred, are two different things. And though we should allow any such
secret Change in the _Air_ to assist in the first Production of the
Disease; yet it may justly be censured in these Writers, that they
should undertake to determine the _Specific Nature_ of these secret
Changes and Alterations, which we have no means at all of discovering:
Since they do not shew themselves in any such sensible manner, as to
come directly under our Examination; nor yet do their Effects, in
producing the _Plague_, point out any thing of their _Specific Nature_.

ALL that we know, is this, that the Cause of the _Plague_, whatever it
be, is of such a Nature, that when taken into the Body, it works such
Changes in the Blood and Juices, as to produce this Disease, by suddenly
giving some Parts of the Humours such corrosive Qualities, that they
either excite inward _Inflammations_ and _Gangrenes_, or push out
_Carbuncles_ and _Bubo's_; the _Matter_ of which, when suppurated,
communicates the like Disease to others: But of the manner how this is
done, I shall discourse in the following Chapter.

CHAP. II.

_Of the Causes which spread the Plague._

I HAVE been thus particular in tracing the _Plague_ up to its first
Origine, in order to remove, as much as possible, all Objection against
what I shall say of the Causes, which excite and propagate it among us.
This is done by _Contagion_. Those who are Strangers to the full Power
of _this_, that is, those who do not understand how subtile it is, and
how widely the Distemper may be sprea