Corpuscles more dense, and something augmented by the Accretion of the
oily and earthy Part of that Moisture. Now the green, without doubt, is
of the same Order with those Colours into which it changeth, because the
Changes are gradual, and those Colours, though usually not very full,
yet are often too full and lively to be of the fourth Order.
_Blues_ and _Purples_ may be either of the second or third Order, but
the best are of the third. Thus the Colour of Violets seems to be of
that Order, because their Syrup by acid Liquors turns red, and by
urinous and alcalizate turns green. For since it is of the Nature of
Acids to dissolve or attenuate, and of Alcalies to precipitate or
incrassate, if the Purple Colour of the Syrup was of the second Order,
an acid Liquor by attenuating its tinging Corpuscles would change it to
a red of the first Order, and an Alcali by incrassating them would
change it to a green of the second Order; which red and green,
especially the green, seem too imperfect to be the Colours produced by
these Changes. But if the said Purple be supposed of the third Order,
its Change to red of the second, and green of the third, may without any
Inconvenience be allow'd.
If there be found any Body of a deeper and less reddish Purple than that
of the Violets, its Colour most probably is of the second Order. But yet
there being no Body commonly known whose Colour is constantly more deep
than theirs, I have made use of their Name to denote the deepest and
least reddish Purples, such as manifestly transcend their Colour in
purity.
The _blue_ of the first Order, though very faint and little, may
possibly be the Colour of some Substances; and particularly the azure
Colour of the Skies seems to be of this Order. For all Vapours when they
begin to condense and coalesce into small Parcels, become first of that
Bigness, whereby such an Azure must be reflected before they can
constitute Clouds of other Colours. And so this being the first Colour
which Vapours begin to reflect, it ought to be the Colour of the finest
and most transparent Skies, in which Vapours are not arrived to that
Grossness requisite to reflect other Colours, as we find it is by
Experience.
_Whiteness_, if most intense and luminous, is that of the first Order,
if less strong and luminous, a Mixture of the Colours of several Orders.
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