bodies. That the _Bononian stone_ shines
no longer then it is either warmed by the Sun-beams, or by the flame of a
Fire or of a Candle, is the general report of those that write of it, and
of others that have seen it. And that heat argues a motion of the internal
parts is (as I said before) generally granted.

But there is one Instance more, which was first shewn to the _Royal
Society_ by Mr. _Clayton_ a worthy Member thereof, which does make this
Assertion more evident then all the rest: And that is, That a _Diamond_
being _rub'd_, _struck_ or _heated_ in the dark, shines for a pretty while
after, so long as that motion, which is imparted by any of those Agents,
remains (in the same manner as a Glass, rubb'd, struck, or (by a means
which I shall elsewhere mention) heated, yields a sound which lasts as long
as the vibrating motion of that _sonorous_ body) several Experiments made
on which Stone, are since published in a Discourse of Colours, by the truly
honourable Mr. _Boyle_. What may be said of those _Ignes fatui_ that appear
in the night, I cannot so well affirm, having never had the opportunity to
examine them my self, nor to be inform'd by any others that had observ'd
them: And the relations of them in Authors are so imperfect, that nothing
can be built on them. But I hope I shall be able in another place to make
it at least very probable, that there is even in those also a Motion which
causes this effect. That the shining of _Sea-water_ proceeds from the same
cause, may be argued from this, That it shines not till either it be beaten
against a Rock, or be some other wayes broken or agitated by Storms, or
Oars, or other _percussing_ bodies. And that the Animal _Energyes_ or
Spirituous _agil_ parts are very active in _Cats eyes_ when they shine,
seems evident enough, because their eyes never shine but when they look
very intensly either to find their prey, or being hunted in a dark room,
when they seek after their adversary, or to find a way to escape. And the
like may be said of the shining _Bellies of Gloworms_; since 'tis evident
they can at pleasure either increase or extinguish that Radiation.

It would be somewhat too long a work for this place _Zetetically_ to
examine, and positively to prove, what particular kind of motion it is that
must be the efficient of Light; for though it be a motion, yet 'tis not
every motion that produces it, since we find there are many bodies very
violently mov'd, which yet afford