of it, because
we may hereafter have occasion to make use of what has been now deliver'd,
to illustrate the Generation of Intermediate Colours; concerning which we
must yet subjoyn this Caution, that to make the Rules about the Emergency
of Colours, fit to be Relied upon, the Corpuscles whereof the Pigments
consist must be such as do not Destroy one anothers Texture, for in case
they do, the produced Colour may be very Different from that which would
Result from the Mixture of other harmless Pigments of the same Colours, as
I shall have Occasion to shew ere long.

_EXPERIMENT XIII._

It may also give much light to an Enquirer into the Nature of Colours, to
know that not only in Green, but in many (if not all) other Colours, the
Light of the Sun passing through Diaphanous Bodies of differing Hues may be
tinged of the same Compound Colour, as if it came from some Painters
Colours of the same Denomination, though this later be exhibited by
Reflection, and be (as the former Experiment declares) manifestly
Compounded of material Pigments. Wherefore to try the Composition of
Colours by Trajection, we provided several Plates of Tinged Glass, which
being laid two at a time one on the top of another, the Object look'd upon
through them both, appear'd of a Compounded Colour, which agrees well with
what we have observ'd in the second Experiment, of Looking against the
Light through differingly Colour'd Papers. But we thought the Experiment
would be more Satisfactory, if we procur'd the Sun-beams to be so Ting'd in
their passage through Plates of Glass, as to exhibit the Compounded Colour
upon a Sheet of White Paper. And though by reason of the Thickness of the
Glasses, the Effect was but Faint, even when the Sun was High and Shin'd
forth clear, yet, we easily remedied that by Contracting the Beams we cast
on them by means of a Convex Burning-glass, which where it made the Beams
much converge Increas'd the Light enough to make the Compounded Colour very
manifest upon the Paper. By this means we observ'd, that the Beams
trajected through Blew and Yellow compos'd a Green, that an intense and
moderate Red did with Yellow make differing degrees of Saffron, and Orange
Tawny Colours, that Green and Blew made a Colour partaking of both, such as
that which some Latin Writers call _Pavonaceus_, that Red and Blew made a
Purple, to which we might add other Colours, that we produc'd by the
Combinations of Glasses differingly Ting'd, but that