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 not such an effect; and there are other
bodies, which to our other senses, seem not mov'd so much, which yet shine.
Thus Water and quick-silver, and most other liquors heated, shine not; and
several hard bodies, as Iron, Silver, Brass, Copper, Wood, &c. though very
often struck with a hammer, shine not presently, though they will all of
them grow exceeding hot; whereas rotten Wood, rotten Fish, Sea water,
Gloworms, &c. have nothing of tangible heat in them, and yet (where there
is no stronger light to affect the Sensory) they shine some of them so
Vividly, that one may make a shift to read by them.
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