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.
Of this last kind is the Whiteness of Froth, Paper, Linnen, and most
white Substances; of the former I reckon that of white Metals to be. For
whilst the densest of Metals, Gold, if foliated, is transparent, and all
Metals become transparent if dissolved in Menstruums or vitrified, the
Opacity of white Metals ariseth not from their Density alone. They being
less dense than Gold would be more transparent than it, did not some
other Cause concur with their Density to make them opake. And this Cause
I take to be such a Bigness of their Particles as fits them to reflect
the white of the first order. For, if they be of other Thicknesses they
may reflect other Colours, as is manifest by the Colours which appear
upon hot Steel in tempering it, and sometimes upon the Surface of melted
Metals in the Skin or Scoria which arises upon them in their cooling.
And as the white of the first order is the strongest which can be made
by Plates of transparent Substances, so it ought to be stronger in the
denser Substances of Metals than in the rarer of Air, Water, and Glass.
Nor do I see but that metallick Substances of such a Thickness as may
fit them to reflect the white of the first order, may, by reason of
their great Density (according to the Tenor of the first of these
Propositions) reflect all the Light incident upon them, and so be as
opake and splendent as it's possible for any Body to be. Gold, or Copper
mix'd with less than half their Weight of Silver, or Tin, or Regulus of
Antimony, in fusion, or amalgamed with a very little Mercury, become
white; which shews