between the blue and yellow a mixture of orange, yellow,
green, blue and indigo, all which together ought to exhibit a dilute and
imperfect green. So the Colours of the third Series all succeed in
order; first, the violet, which a little interferes with the red of the
second order, and is thereby inclined to a reddish purple; then the blue
and green, which are less mix'd with other Colours, and consequently
more lively than before, especially the green: Then follows the yellow,
some of which towards the green is distinct and good, but that part of
it towards the succeeding red, as also that red is mix'd with the violet
and blue of the fourth Series, whereby various degrees of red very much
inclining to purple are compounded. This violet and blue, which should
succeed this red, being mixed with, and hidden in it, there succeeds a
green. And this at first is much inclined to blue, but soon becomes a
good green, the only unmix'd and lively Colour in this fourth Series.
For as it verges towards the yellow, it begins to interfere with the
Colours of the fifth Series, by whose mixture the succeeding yellow and
red are very much diluted and made dirty, especially the yellow, which
being the weaker Colour is scarce able to shew it self. After this the
several Series interfere more and more, and their Colours become more
and more intermix'd, till after three or four more revolutions (in which
the red and blue predominate by turns) all sorts of Colours are in all
places pretty equally blended, and compound an even whiteness.

And since by the 15th Observation the Rays endued with one Colour are
transmitted, where those of another Colour are reflected, the reason of
the Colours made by the transmitted Light in the 9th and 20th
Observations is from hence evident.

If not only the Order and Species of these Colours, but also the precise
thickness of the Plate, or thin Body at which they are exhibited, be
desired in parts of an Inch, that may be also obtained by assistance of
the 6th or 16th Observations. For according to those Observations the
thickness of the thinned Air, which between two Glasses exhibited the
most luminous parts of the first six Rings were 1/178000, 3/178000,
5/178000, 7/178000, 9/178000, 11/178000 parts of an Inch. Suppose the
Light reflected most copiously at these thicknesses be the bright
citrine yellow, or confine of yellow and orange, and these thicknesses
will be F[Greek: l], F[Greek: m], F[Greek: u], F[G