cribed,
which are severally illuminated by homogeneal Rays, by interfering with
one another, and being every where commix'd, do render the Light
sufficiently compound. But if these Circles, whilst their Centers keep
their Distances and Positions, could be made less in Diameter, their
interfering one with another, and by Consequence the Mixture of the
heterogeneous Rays would be proportionally diminish'd. In the twenty
third Figure let AG, BH, CJ, DK, EL, FM be the Circles which so many
sorts of Rays flowing from the same disque of the Sun, do in the third
Experiment illuminate; of all which and innumerable other intermediate
ones lying in a continual Series between the two rectilinear and
parallel edges of the Sun's oblong Image PT, that Image is compos'd, as
was explained in the fifth Experiment. And let _ag_, _bh_, _ci_, _dk_,
_el_, _fm_ be so many less Circles lying in a like continual Series
between two parallel right Lines _af_ and _gm_ with the same distances
between their Centers, and illuminated by the same sorts of Rays, that
is the Circle _ag_ with the same sort by which the corresponding Circle
AG was illuminated, and the Circle _bh_ with the same sort by which the
corresponding Circle BH was illuminated, and the rest of the Circles
_ci_, _dk_, _el_, _fm_ respectively, with the same sorts of Rays by
which the several corresponding Circles CJ, DK, EL, FM were illuminated.
In the Figure PT composed of the greater Circles, three of those Circles
AG, BH, CJ, are so expanded into one another, that the three sorts of
Rays by which those Circles are illuminated, together with other
innumerable sorts of intermediate Rays, are mixed at QR in the middle
of the Circle BH. And the like Mixture happens throughout almost the
whole length of the Figure PT. But in the Figure _pt_ composed of the
less Circles, the three less Circles _ag_, _bh_, _ci_, which answer to
those three greater, do not extend into one another; nor are there any
where mingled so much as any two of the three sorts of Rays by which
those Circles are illuminated, and which in the Figure PT are all of
them intermingled at BH.

Now he that shall thus consider it, will easily understand that the
Mixture is diminished in the same Proportion with the Diameters of the
Circles. If the Diameters of the Circles whilst their Centers remain the
same, be made three times less than before, the Mixture will be also
three times less; if ten times less, the Mixture will