the Particles of
Substances, turn them to black, why small quantities of black Substances
impart their Colour very freely and intensely to other Substances to
which they are applied; the minute Particles of these, by reason of
their very great number, easily overspreading the gross Particles of
others; why Glass ground very elaborately with Sand on a Copper Plate,
'till it be well polish'd, makes the Sand, together with what is worn
off from the Glass and Copper, become very black: why black Substances
do soonest of all others become hot in the Sun's Light and burn, (which
Effect may proceed partly from the multitude of Refractions in a little
room, and partly from the easy Commotion of so very small Corpuscles;)
and why blacks are usually a little inclined to a bluish Colour. For
that they are so may be seen by illuminating white Paper by Light
reflected from black Substances. For the Paper will usually appear of a
bluish white; and the reason is, that black borders in the obscure blue
of the order described in the 18th Observation, and therefore reflects
more Rays of that Colour than of any other.

In these Descriptions I have been the more particular, because it is not
impossible but that Microscopes may at length be improved to the
discovery of the Particles of Bodies on which their Colours depend, if
they are not already in some measure arrived to that degree of
perfection. For if those Instruments are or can be so far improved as
with sufficient distinctness to represent Objects five or six hundred
times bigger than at a Foot distance they appear to our naked Eyes, I
should hope that we might be able to discover some of the greatest of
those Corpuscles. And by one that would magnify three or four thousand
times perhaps they might all be discover'd, but those which produce
blackness. In the mean while I see nothing material in this Discourse
that may rationally be doubted of, excepting this Position: That
transparent Corpuscles of the same thickness and density with a Plate,
do exhibit the same Colour. And this I would have understood not without
some Latitude, as well because those Corpuscles may be of irregular
Figures, and many Rays must be obliquely incident on them, and so have
a shorter way through them than the length of their Diameters, as
because the straitness of the Medium put in on all sides within such
Corpuscles may a little alter its Motions or other qualities on which
the Reflexion depends. But yet