or take fire and burn; but a part also which is fixt, terrestrial, and
irrarefiable.

Ninthly, that as there are these several parts that will rarifie and fly,
or be driven up by the heat, so are there many others, that as they are
indissoluble by the _aerial menstruum_, so are they of such sluggish and
gross parts, that they are not easily rarify'd by heat, and therefore
cannot be rais'd by it; the volatility or fixtness of a body seeming to
consist only in this, that the one is of a texture, or has component parts
that will be easily rarify'd into the form of Air, and the other, that it
has such as will not, without much ado, be brought to such a constitution;
and this is that part which remains behind in a white body call'd Ashes,
which contains a substance, or _Salt_, which Chymists call _Alkali_: what
the particular natures of each of these bodies are, I shall not here
examine, intending it in another place, but shall rather add that this
_Hypothesis_ does so exactly agree with all _Phaenomena_, of Fire, and so
genuinely explicate each particular circumstance that I have hitherto
observ'd, that it is more then probable, that this cause which I have
assign'd is the true adequate, real, and onely cause of those _Phaenomena_;
And therefore I shall proceed a little further, to shew the nature and use
of the Air.

Tenthly, therefore the dissolving parts of the Air are but few, that is, it
seems of the nature of those _Saline menstruums_, or spirits, that have
very much flegme mixt with the spirits, and therefore a small parcel of it
is quickly glutted, and will dissolve no more; and therefore unless some
fresh part of this _menstruum_ be apply'd to the body to be dissolv'd, the
action ceases, and the body leaves to be dissolv'd and to shine, which is
the Indication of it, though plac'd or kept in the greatest heat; whereas
_Salt-peter_ is a _menstruum_, when melted and red-hot, that abounds more
with those Dissolvent particles, and therefore as a small quantity of it
will dissolve a great sulphureous body, so will the dissolution be very
quick and violent.

Therefore in the _Eleventh_ place, it is observable, that, as in other
solutions, if a copious and quick supply of fresh _menstruum_, though but
weak, be poured on, or applied to the dissoluble body, it quickly consumes
it: So this _menstruum_ of the Air, if by Bellows, or any other such
contrivance, it be copiously apply'd to the shining body, is found to
dissolv