or
Slowness of their Revolution or Rotation in reference to their Progressive
Motion, but their more Absolute Celerity, their Direct or Undulating
Motion, and other Accidents, which may attend their Appulse to the Eye, may
fit them to make Differing Impressions on it.

4. Secondly, For these and the like Considerations, _Pyrophilus_, I must
desire that you would look upon this little Treatise, not as a Discourse
written Principally to maintain any of the fore-mention'd Theories,
Exclusively to all others, or substitute a New one of my Own, but as the
beginning of a History of Colours, upon which, when you and your Ingenious
friends shall have Enrich'd it, a Solid Theory may be safely built. But yet
because this History is not meant barely for a Register of the things
recorded in it, but for an _Apparatus_ to a sound and comprehensitive
Hypothesis, I thought fit, so to temper the whole Discourse, as to make it
as conducible, as conveniently I can to that End, and therefore I have not
scrupled to let you see that I was willing, as to save you the labour of
Cultivating some Theories that I thought would never enable you to reach
the Ends you aim at, so to contract your Enquiries into a Narrow compass,
for both which purposes I thought it requisite to do these two things, the
_One_, to set down some Experiments which by the help of the Reflections
and Insinuations that attend them, may assist you to discover the
Infirmness and Insufficiency both of the common Peripatetick Doctrine, and
of the now more applauded Theory of the _Chymists_ about Colour, because
those two Doctrines having Possess'd themselves, the one of the most part
of the Schools, and the other of the Esteem of the Generality ef Physicians
and other Learned Men, whose Professions and Ways of Study do not exact
that they should Scrupulously examine the very First and Simplest
Principles of Nature, I fear'd it would be to little purpose, without doing
something to discover the Insufficiency of these Hypotheses, that I should,
(which was the _Other_ thing I thought requisite for me to do) set down
among my other Experiments those in the greatest Number, that may let you
see, that, till I shall be Better Inform'd, I encline to take Colour to be
a Modification of Light, and would invite you chiefly to Cultivate that
Hypothesis, and Improve it to the making out of the Generation of
Particular Colours, as I have Endeavour'd to apply it to the Explication of
Whiteness