[2IS]

of pap, then melted in a crucible, and poured into a flat mould)first well warmed. The person, who communicated this.receipt to Dr. Hooke, fays that the metal will not onlyappear, but work, like coarse gold ; that he sold it as dearas silver; and that the king of Poland had a service of it,only mixing fifteen ounces of gold with a hundred of thecompound metal. I tried this process with verdegris, whichI had myself purified, by dissolving it in distilled vinegar,and evaporating the filtered solution to dryness: a largeproportion of the verdegris remained undissolved ; and thisresiduum, on being melted with black flux, yielded a brittlepale coloured metal almost like bell-metal: from whenceit might be presumed, that the copper, in the inspissatedmatter, was rendered purer than ordinary by the sepa-ration of this extraneous metal. On melting it withchoice tutty, and the other ingredients, the result wasa very fine metal, which bore the hammer well; but itwas rather a sine brass than a true gold coloured metal,its colour having less resemblance to gold than that ofthe mixture of equal parts of common copper and zinc-already mentioned.

Tutty and calamine contain zinc in a state of calx ;and hence, in the use of these, inflammable additions areessentially necessary, for reviving the zinc into its me-tallic form. Some of the earlier writers direct for thispurpose substances of a yellow colour, as turmeric, rhu-barb, saffron, aloes, which are still used, as I am inform-ed, by several workmen, who do not seem to have con-sidered, that these kinds of substances can be of serviceno otherwise than as they furnish- an inflammable matter,and that common charcoal answers the same end*

Two ways have been recommended, for giving agold colour to copper, and at the same time preservingits malleability, without the addition of any zinc, or of

i substances.