_Exper._ 13. In the homogeneal Light I placed a Paper Circle of a
quarter of an Inch in diameter, and in the Sun's unrefracted
heterogeneal white Light I placed another Paper Circle of the same
Bigness. And going from the Papers to the distance of some Feet, I
viewed both Circles through a Prism. The Circle illuminated by the Sun's
heterogeneal Light appeared very oblong, as in the fourth Experiment,
the Length being many times greater than the Breadth; but the other
Circle, illuminated with homogeneal Light, appeared circular and
distinctly defined, as when 'tis view'd with the naked Eye. Which proves
the whole Proposition.
_Exper._ 14. In the homogeneal Light I placed Flies, and such-like
minute Objects, and viewing them through a Prism, I saw their Parts as
distinctly defined, as if I had viewed them with the naked Eye. The same
Objects placed in the Sun's unrefracted heterogeneal Light, which was
white, I viewed also through a Prism, and saw them most confusedly
defined, so that I could not distinguish their smaller Parts from one
another. I placed also the Letters of a small print, one while in the
homogeneal Light, and then in the heterogeneal, and viewing them through
a Prism, they appeared in the latter Case so confused and indistinct,
that I could not read them; but in the former they appeared so distinct,
that I could read readily, and thought I saw them as distinct, as when I
view'd them with my naked Eye. In both Cases I view'd the same Objects,
through the same Prism at the same distance from me, and in the same
Situation. There was no difference, but in the Light by which the
Objects were illuminated, and which in one Case was simple, and in the
other compound; and therefore, the distinct Vision in the former Case,
and confused in the latter, could arise from nothing else than from that
difference of the Lights. Which proves the whole Proposition.
And in these three Experiments it is farther very remarkable, that the
Colour of homogeneal Light was never changed by the Refraction.
_PROP._ VI. THEOR. V.
_The Sine of Incidence of every Ray considered apart, is to its Sine of
Refraction in a given Ratio._
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