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.
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