5. Thirdly. But, _Pyrophilus_, though this be at present the Hypothesis I
preferr, yet I propose it but in a General Sense, teaching only that the
Beams of Light, Modify'd by the Bodies whence they are sent (Reflected or
Refracted) to the Eye, produce there that Kind of Sensation, Men commonly
call Colour; But whether I think this Modification of the Light to be
perform'd by Mixing it with Shades, or by Varying the Proportion of the
Progress and Rotation of the _Cartesian Globuli Cælestes_, or by some other
way which I am not now to mention, I pretend not here to Declare. Much less
do I pretend to Determine, or scarce so much as to Hope to know all that
were requisite to be Known, to give You, or even my Self, a perfect account
of the Theory of Vision and Colours, for in Order to such an undertaking I
would first Know what Light is, and if it be a Body (as a Body or the
Motion of a Body it seems to be) what Kind of Corpuscles for Size and Shape
it consists of, with what Swiftness they move Forwards, and Whirl about
their own Centres. Then I would Know the Nature of Refraction, which I take
to be one of the Abstrusest things (not to explicate Plausibly, but to
explicate Satisfactorily) that I have met with in Physicks; I would further
Know what Kind and what Degree of Commixture of Darkness or Shades is made
by Refractions or Reflections, or both, in the Superficial particles of
those Bodies, that being Shin'd upon, constantly exhibit the one, for
Instance, a Blew, the other a Yellow, the third a Red Colour; I would
further Know why this Contemperation of Light and Shade, that is made, for
Example, by the Skin of a Ripe Cherry, should exhibit a Red, and not a
Green, and the Leaf of the same Tree should exhibit a Green rather than a
Red; and indeed, Lastly, why since the Light that is Modify'd into these
Colours consists but of Corpuscles moved against the _Retina_ or Pith of
the Optick Nerve, it should there not barely give a Stroak, but produce a
Colour, whereas a Needle wounding likewise the Eye, would not produce
Colour but Pain. These, and perhaps other things I should think requisite