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also by barely beating Gold into such thin leaves as Artificers and Apothecaries are wont to employ, it will be brought to exhibite a green Colour, when you hold it against the Light, whether of the day, or of a good Candle; and this kind of Greenness as 'tis permanent in the foliated Gold, so I have found by trial, that if the Sun-beams, somewhat united by a Burning-glass, be trajected through the expanded Leaf, and cast upon a piece of white paper, they will appear there as if they had been tinged in their passage. Nay, and sometimes a slight and almost momentany Mechanical change will seem to over rule Nature, and introduce into a body the quite opposite Quality to that she had given it: As when a piece of black Horn is, onely by being thinly scraped with the edge of a knife or a piece of glass, reduced to permanently white Shavings. And to these Instances of Colours, some Emphatical and some Permanent, might be added divers belonging to other Qualities, but that I ought not to anticipate what you will elsewhere meet with.
There is yet another way of arguing in favour of the Corpuscularian Doctrine of Qualities, which, though it do not afford direct proofs of its being the bestHypo-
