The works of the Honourable Robert Boyle, Esq., epitomiz'd by Richard Boulton ... ; illustrated with copper plates.

EXPERIMENT XI.

I Have a flat Piece of Glass, which held be∣twixt my Eye and the light appears Yellow; but being held so, that it reflects fewer Beams upon the Eye, it degenerates into to a pale Blew. And the same Piece of Glass being held Perpendicular to the Horizon, that Part which the Sun shines on will be of a more dilute Yel∣low, than the other which is shaded; but if it be held Perpendicular to the Horizon, the shaded Part will be of a Golden Colour and the other Blew; if the Sun-beams pass through it upon a white Paper, they will represent a Yellow; yet the Position may be so vary'd, as to yield a mix'd Colour more or less inclining to Yellow in some Places and in others to Blew. N. 1st In trying of these Experiments, the Sun-beams must fall upon the superficial Parts of one side of the Glass, on which we must take care to keep our Eye. And we have prepar'd a sort of Glass which would answer our expectation by laying a Leaf of Silver on one side, and urging it with a stronger Fire than usual. And one thing

in this Experiment remarkable was, that where∣as common Artificers colour their Glass by put∣ting a Calx of Silver, Calcin'd without corro∣sive Liquors, and temper'd with fair Water, on the Plates of Glass when they burn them, theirs appears Yellow whatever side is held to the Eye, or in whatever Posture, but this of ours held betwixt the Eye and the Light appear'd Tran∣sparently Yellow; but the Eye being placed be∣twixt the Light and it, it appear'd Blew, and not in the least Transparent.