omes from the electric matter itself;
and this being a modification of phlogiston, it is probable that _all
light_ is a modification of phlogiston also. Indeed, since no other
substances besides such as contain phlogiston are capable of ignition,
and consequently of becoming luminous, it was on this account pretty
evident, prior to these deductions from electrical phenomena, that light
and phlogiston are the same thing, in different forms or states.

It appears to me that _heat_ has no more proper connexion with
phlogiston than it has with water, or any other constituent part of
bodies; but that it is a state into which the parts of bodies are thrown
by their action and reaction with respect to one another; and probably
(as the English philosophers in general have supposed) the heated state
of bodies may consist of a subtle vibratory motion of their parts. Since
the particles which constitute light are thrown from luminous bodies
with such amazing velocity, it is evident that, whatever be the cause of
such a projection, the reaction consequent upon it must be considerable.
This may be sufficient not only to keep up, but also to increase the
vibration of the parts of those bodies in which the phlogiston is not
very firmly combined; and the difference between the substances which
are called _inflammable_ and others which also contain phlogiston may be
this, that in the former the heat, or the vibration occasioned by the
emission of their own phlogiston, may be sufficient to occasion the
emission of more, till the whole be exhausted; that is, till the body be
reduced to ashes. Whereas in bodies which are not inflammable, the heat
occasioned by the emission of their own phlogiston may not be sufficient
for this purpose, but an additional heat _ab extra_ may be necessary.

Some philosophers dislike the term _phlogiston_; but, for my part, I can
see no objection to giving that, or any other name, to a _real
something_, the presence or absence of which makes so remarkable
difference in bodies, as that of _metallic calces_ and _metals_, _oil of
vitriol_ and _brimstone_, &c. and which may be transferred from one
substance to another, according to certain known laws, that is, in
certain definite circumstances. It is certainly hard to conceive how any
thing that answers this description can be only a mere _quality_, or
mode of bodies, and not _substance_ itself, though incapable of being
exhibited alone. At least, there can be no