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receive these imperfections from an admixture of emery.The gold is to be melted with equal its weight of bismuth,and so much poured out as is fluid enough to run : to theremainder is to be added equal its weight more of bis-muth, and this procedure repeated till the whole of thegold has run thin from the crucible. The mixt is putinto a large thick cupel or test, included in a mould ofcrucible earth ; by a suitable fire, the bismuth works offas lead does, leaving the gold still impure and coveredwith a livid skin. For every eight ounces of gold, twoor three ounces of lead are then to be added, and the firecontinued till the lead is worked oft': the gold is stillfound not sufficiently fine, though less brittle and lesslivid than it was before. It is now to be melted in aforge or blast furnace, and the flame impelled by thebellows upon the surface of the metal, till it begins togrow clear ; after which the repeated injection of somemercury-sublimate, with a little borax towards the end,completes the purification.

I have not had an opportunity of examining this process,having never met with any gold that had the charactersof impurity above described, except such as was mixedwith platina, which I did not find to be benefited by thistreatment.

II. Separation of gold from silver by aqua forth.

Parting with aqua fords is one of the most commonoperations, both for purifying gold from a little silver,and for extracting a little gold from a large proportion ofsilver. Frequently both intentions are answered at once :for when gold is thus to be purified, it requires, as wehave already seen, an addition of silver, and such silver ascontains gold is always preferred for this use so that

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