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quill in the side os the tub, carries with it the lighterearthy matter: fresh water is supplied till all the earth isthus washed off. The operation might doubtless beexpedited by the use of heat, as in the above processof Barba.

The gold being by these means transferred into themercury, and the mixture washed clean, as much as maybe of the mercury is pressed out through leather, and theremainder forced off by fire. To collect the exhalingmercury, a head and receiver are fitted to the iron pot inwhich the mass is exposed to the fire : Barba advises thepot to be lined with a mixture of clay and sand, toprevent the gold from adhering to or dissolving a part ofthe iron in case the fire should be raised so far as to makethe gold melt.

It is scarcely to be expected, that the greatest addressof the workman can collect, either by water or mercury,the whole of the gold diffused through a large quantityof other matter; at least when the mercury is used, as itis in the large way, in so small a proportion as a hundredthor a two hundredth part of the weight of the earthy pow-der. Reaumur, after having worked some gold sandwith mercury, in the method commonly practised bythose who wash the sands of rivers, obtained, from theremaining land, by treating it with a double quantity ofmercury, near as much gold as he had done the firsttime.

IV. Extraction of gold intimately combined in the composition

of sands.

For extracting gold from the ferrugineous sands men-tioned in the preceding part of this section, the sand is tobe made red hot and quenched in water, and the ignition

C c 2 and