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os lead necessary for scorifying so large a proportion ofcopper, and the difficult revival of the copper from thescoria, render the process too expensive for the produceof gold.

Some have melted the gold-holding copper with aboutthrice its quantity of lead, and cast the mixture into cakeswhich being ranged in the higher part of a hoping canal,and moderately heated, it was expected that the lead,melting out and running down from the copper, wouldcarry the gold with it. But though this process succeedsfor the separation of silver from copper, it is otherwise inregard to gold : if the copper contains both gold andsilver, only the silver melts out with the lead, the gold re-maining behind in the unmelted mass of copper.

Alonso Barb a gives a method which may in severalcafes be practicable to advantage. The copper is calcinedwith sulphur, till it becomes pulverable, and the powderground with quicksilver in the fame manner as earthy orstony bodies containing gold : the mercury imbibes thegold, without acting upon the calcined copper, which maynow be washed off with water.

Many processes have been given for separating gold fromcopper by precipitating powders, which are composed ofvery discordant materials, as antimony, lead, sulphur*crocus of iron, mercury-fublimate, arsenic, vitriol, ver-degris, alum, nitre, sal ammoniac, wood ashes, quick-lime. Though these processes, a number of which iscollected by Swedenborg in the third volume of his regnumsubterraneum, are apparently so injudicious, that an artistcan have no inducement to make trial of them, yet theyare not altogether without foundation : lead and sulphur,as Barba intimates, and as an experiment of Mr. Scheffer’shas shewn more satisfactorily, are the useful ingredients;and by means of these ingredients, gold may be extracted

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