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kneaded, a gentle heat is applied, by which the activityof the mercury is so far increased, that the incorporation-of the gold with it, which in the cold requires aboutthirty days, is said by J. Hernandez, in an essay on thesemines, to be effected by this method in five or six days.

Alonfo Barba, in the third book of his art of metals,,describes another method, which he fays he has practisedwith great advantage : he puts the powder, with a suitablequantity of mercury and water, into a deep copper vesselfixed in a furnace, and applies a fire sufficient to keep thewater boiling : a small wooden mill assists the ebullition,of the water in giving motion to the earthy powder,,which continually rising and falling down again, is broughtinto frequent contact with the mercury at the bottom, fe*as to give out its gold to the mercury in as many hours,,as the common process without heat requires days.

When the gold is judged to be united with the mer-cury, the earthy powder is washed off by water, so as toleave the amalgam clean. Where the mercury has beenkneaded up with the powder, a considerable part of it isalways divided into such minute globules as to be washedaway along with the earth j an inconvenience which inthe other method does not happen or in a far less degree.

The gold dust or filings dispersed through the sweepingsof the goldsmiths shops, are recovered also-by amalgama-tion with mercury. Two broad iron bars, rounded atthe ends, placed crosswise and fixed on an upright axis,'are made to turn, by a handle at the top, on an iron planefitted into the bottom of a tub. The sweepings being putinto the tub with a quantity of mercury and water, thepowder, pasting successively under the iron bars, is groundand brought into contact with the quicksilver, whichby degrees extracts the gold ; while the water, which,after a certain time is suffered to run off through a small

quill