hat like that of a Turquoise.
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. And next, that we have our selves made Glasses not
unfit to exhibit an Experiment not unlike that I have been speaking of, by
laying upon pieces of Glass some very finely foliated Silver, and giving it
by degrees a much stronger Fire than is requisite or usual for the Tinging
of Glasses of other Colours. And this Experiment, not to mention that it
was made without a Furnace in which Artificers that Paint Glass are wont to
be very Curious, is the more considerable, because, that though a Skilfull
Painter could not deny to me that 'twas with Silver he Colour'd his Glasses
Yellow; yet he told me, that when to Burn them (as they speak) he layes on
the plates of Glass nothing but a _Calx_ of Silver Calcin'd without
Corrosive Liquors, and Temper'd with Fair Water, the Plates are Ting'd of a
fine Yellow that looks of a Golden Colour, which part soever of it you turn