And not only if you look upon a Glass half full of _Aqua-fortis_, or Spirit
of _Nitre_, and half full of _Nitrous_ steams proceeding from it, you will
see the Upper part of the Glass of the Colour freshly mention'd, if through
it you look upon the Light. But which is much more considerable, I have
tried, that putting _Aqua-fortis_ in a long clear Glass, and adding a
little Copper or some such open Metall to it, to excite Heat and Fumes, the
Light trajected through those Fumes, and cast upon a sheet of White Paper,
did upon that appear of the Colour that the Fumes did, when directly Look'd
upon, as if the Light were as well Ting'd in its passage through these
Fumes, as it would have been by passing through some Glass or Liquor in
which the same Colour was Inherent.
To which I shall further add, that having sometimes had the Curiosity to
observe whether the Beams of the Sun near the Horizon trajected through a
very Red Sky, would not (though such rednesses are taken to be but
Emphatical Colours) exhibit the like Colour, I found that the Beams falling
within a Room upon a very White Object, plac'd directly opposite to the
Sun, disclos'd a manifest Redness, as if they had pass'd through a Colour'd
_Medium_.
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