rk Orange Tawny.

The Green and Purple made the Purple appear more Dirty.

The Blew and Purple made the Purple more Lovely, and far more Deep.

The Red parts of the Marbl'd Paper look'd upon with the Yellow appear'd of
a Red far more like Scarlet than without it.

[Page 191]
But the Fineness or Coarseness of the Papers, their being carefully or
slightly Colour'd, and divers other Circumstances, may so vary the Events
of such Experiments as these, that if, _Pyrophilus_, you would Build much
on them, you must carefully Repeat them.

_EXPERIMENT IV._

The Triangular Prismatical Glass being the Instrument upon whose Effects we
may the most Commodiously speculate the Nature of Emphatical Colours, (and
perhaps that of Others too;) we thought it might be usefull to observe the
several Reflections and Refractions which the Incident Beams of Light
suffer in Rebounding from it, and Passing through it. And this we thought
might be Best done, not (as is usual,) in an ordinary Inlightn'd Room,
where (by reason of the Difficulty of doing otherwise) ev'n the Curious
have left Particulars Unheeded, which may in a convenient place be easily
taken notice of; but in a Darken'd Room, where by placing the Glass in a
convenient Posture, the Various Reflections and Refractions may be
Distinctly observ'd; and where it may appear _what_ Beams are Unting'd; and
_which_ they are, that upon the Bodyes that terminate them, do Paint either
the Primary or Secondary Iris. In pursuance of this we did in the above
mention'd Darken'd Room, make observation of no less than four Reflections,
and three Refractions that were afforded us by the same Prism, and thought
that notwithstanding what was taught us by the Rules of Catoptricks and
Dioptricks, it would not be amiss to find also, by hiding sometimes one
part of the Prism, and sometimes another, and observing where the Light or
Colour Vanish'd thereupon, by which Reflection and by which Refraction each
of the several places whereon the Light rebounding from, or passing
through, the Prism appear'd either Sincere or Tincted, was produc'd. But
because it would be Tedious and not so Intelligible to deliver this in
Words, I have thought fit to Referr You to the Annexed Scheme where the
Newly mention'd particulars may be at one View taken Notice of.

_EXPERIMENT V._

[Illustration: _The Explication of the Scheme._]

_PPP_. An Aequilaterot