sing'y Insensible, and therefore small enough to be capable of being such
Minute Particles as the _Atomists_ both of old and of late have (not
absurdly) called _Corpuscula Coloris_, may not yet consist each of them of
divers yet Minuter Particles, betwixt which we may conceive little
Commissures where they Adhere to one another, and, however, may not be
Porous enough to be, at least in some degree, Pervious to the unimaginably
subtile Corpuscles that make up the Beams of Light, and consequently to be
in such a degree Diaphanous. For, _Pyrophilus_, that the proposed Enquiry
may be of moment to him that searches after the Nature of Colour, you'l
easily grant, if you consider, that whereas Perfectly Opacous bodies can
but reflect the incident Beams of Light, those that are Diaphanous are
qualified to refract them too, and that Refraction has such a stroak in the
Production of Colours, as you cannot but have taken notice of, and perhaps
admir'd in the Colours generated by the Trajection of Light through Drops
of Water that exhibit a Rain-bow, through Prismatical glasses, and through
divers other Transparent bodies. But 'tis like, _Pyrophilus_, you'l more
easily allow that about this matter 'tis rather Important to have a
Certainty, than that 'tis Rational to entertain a Doubt; wherefore I must
mention to you some of the Reasons that make me think it may need a further
Enquiry, for I find that in a Darkned Room, where the Light is permitted to
enter but at One hole, the little wandering Particles of Dust, that are
commonly called Motes, and, unless in the Sunbeams, are not taken notice of
by the unassisted Sight, I have, I say, often observ'd, that these roving
Corpuscles being look'd on by an Eye plac'd on one side of the Beams that
enter'd the Little hole, and by the Darkness having its Pupill much
Enlarg'd, I could discern that these Motes as soon as they came within the
compass of the Luminous, whether Cylinder or Inverted Cone, if I may so
call it, that was made up by the Unclouded Beams of the Sun, did in certain
positions appear adorn'd with very vivid Colours, like those of the
Rain-bow, or rather like those of very Minute, but Sparkling fragments of