Affording us this
particular negative Information, that for the production of Colours there
is not necessary either a great refraction, as in the Prisme; nor Secondly,
a determination of Light and shadow, such as is both in the Prisme and
Glass-ball. Now that we may see likewise what affirmative and positive
Instruction it yields, it will be necessary, to examine it a little more
particularly and strictly; which that we may the better do, it will be
requisite to premise somewhat in general concerning the nature of Light and
Refraction.
And first for Light it seems very manifest, that there is no luminous Body
but has the parts of it in motion more or less.
First, That all kind of _fiery burning Bodies_ have their parts in motion,
I think, will be very easily granted me. That the _spark_ struck from a
Flint and Steel is in a rapid agitation, I have elsewhere made probable.
And that the Parts of _rotten Wood_, _rotten Fish_ and the like, are also
in motion, I think, will as easily be conceded by those, who consider, that
those parts never begin to shine till the Bodies be in a state of
putrefaction; and that is now generally granted by all, to be caused by the
motion of the parts of putrifying 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.
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