cident Beams of Light from rebounding plentifully enough to the Eye. To
be short, those I reason with, do concerning Blackness, what the Chymists
are wont also to do concerning other Qualities, namely to content
themselves to tell us, in what Ingredient of a Mixt Body, the Quality
enquir'd after, does reside, instead of explicating the Nature of it, which
(to borrow a comparison from their own Laboratories) is much as if in an
enquiry after the cause of Salivation, they should think it enough to tell
us, that the several Kinds of Praecipitates of Gold and _Mercury_) as
likewise of Quick-silver and Silver (for I know that make and use of such
Precipitates also) do Salivate upon the account of the _Mercury_, which
though Disguis'd abounds in them, whereas the Difficulty is as much to know
upon what account _Mercury_ it self, rather than other Bodies, has that
power of working by Salivation. Which I say not, as though it were not
_something_ (and too often the most we can arrive at) to discover in which
of the Ingredients of a Compounded Body, the Quality, whose Nature is
sought, resides, but because, though this Discovery it self may pass for
_something_, and is oftentimes more than what is taught us about the same
subjects in the Schools, yet we ought not to think it _enough_, when more
Clear and Particular accounts are to be had.

* * * * *

THE
Experimental History
OF
COLOURS
Begun.

* * * * *

The Third PART.

* * * * *

Containing
Promiscuous Experiments
About
COLOURS.

* * * * *

EXPERIMENT I.

Because that, according to the Conjectures I have above propos'd, one of
the most General Causes of the Diversity of Colours in Opacous Bodyes, is,
that some reflect the Light mingl'd with more, others with less of Shade
(either as to Quantity, or as to Interruption) I hold it not unfit to
mention in the first place, the Experiments that I thought upon to examine
this Conjecture. And though coming to transcribe them out of some
Physiological _Adversaria_ I had written in loose Papers, I cannot find one
of the chief Records I had of my Tryals of this Nature, yet the Papers that
scap'd miscarrying,