there partly upon P by a greater Refraction, partly upon T by a less
Refraction, and partly upon R and other intermediate places by
intermediate Refractions. By turning the Parallelopiped ACBD about its
Axis, according to the order of the Letters A, C, D, B, at length when
the contiguous Planes BC and CB become sufficiently oblique to the Rays
FM, which are incident upon them at M, there will vanish totally out of
the refracted Light OPT, first of all the most refracted Rays OP, (the
rest OR and OT remaining as before) then the Rays OR and other
intermediate ones, and lastly, the least refracted Rays OT. For when
the Plane BC becomes sufficiently oblique to the Rays incident upon it,
those Rays will begin to be totally reflected by it towards N; and first
the most refrangible Rays will be totally reflected (as was explained in
the preceding Experiment) and by Consequence must first disappear at P,
and afterwards the rest as they are in order totally reflected to N,
they must disappear in the same order at R and T. So then the Rays which
at O suffer the greatest Refraction, may be taken out of the Light MO
whilst the rest of the Rays remain in it, and therefore that Light MO is
compounded of Rays differently refrangible. And because the Planes AB
and CD are parallel, and therefore by equal and contrary Refractions
destroy one anothers Effects, the incident Light FM must be of the same
Kind and Nature with the emergent Light MO, and therefore doth also
consist of Rays differently refrangible. These two Lights FM and MO,
before the most refrangible Rays are separated out of the emergent Light
MO, agree in Colour, and in all other Properties so far as my
Observation reaches, and therefore are deservedly reputed of the same
Nature and Constitution, and by Consequence the one is compounded as
well as the other. But after the most refrangible Rays begin to be
totally reflected, and thereby separated out of the emergent Light MO,
that Light changes its Colour from white to a dilute and faint yellow, a
pretty good orange, a very full red successively, and then totally
vanishes. For after the most refrangible Rays which paint the Paper at
P with a purple Colour, are by a total Reflexion taken out of the beam
of Light MO, the rest of the Colours which appear on the Paper at R and
T being mix'd in the Light MO compound there a faint yellow, and after
the blue and part of the green which appear on the Paper between P and R
are taken