And what which may also appear strange, is this, that if in a certain
posture you hold one of these Plates Perpendicular to the Horizon, so that
the Sun-beams shine upon half of it, the other half being Shaded, You may
see that the part Shin'd upon will be of a much Diluter Yellow than the
Shaded part which will appear much more Richly Colour'd; and if You alter
the Posture of the Glass, so that it be not held Perpendicular, but
Parallel in reference to the Horizon, You may see, (which perhaps you will
admire) the Shaded part look of a Golden Colour, but the other that the Sun
shines freely on, will appear considerably Blew, and as you remove any part
of the Glass thus held Horizontally into the Sun-beams or Shade, it will in
the twinkling of an Eye seem to pass from one of the above mention'd
Colours to the other, the Sun-beams Trajected through it upon a sheet of
White Paper held near it, do colour it with a Yellow, somewhat bordering
upon a Red, but yet the Glass may be so oppos'd to the Sun, that it may
upon Paper project a mix'd Colour here and there more inclin'd to Yellow,
and here and there more to Blew. The other Phaenomena of this odd Glass, I
fear it would be scarce worth while to Record, and therefore I shall rather
advertise You, _First_ that in the trying of these Experiments with it, you
must take notice that one of the sides has either alone, or at least
principally its Superficial parts dispos'd to the Reflection of the Blew
Colour above nam'd, and that therefore you must have a care to keep that
side nearest to the Eye.
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