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then very imperfectly known, some deception happened inthis point. Mr. Wood relates, that platina having beenmelted in an assay furnace on a test with lead, and there-with exposed to a great fire for three hours, till all the leadwas wrought off, the platina was afterwards found remain-ing at the bottom of tire test, without having suffered anyalteration or diminution by this operation. Dr.Brownrigg,surprized at this resistence of platina to lead, repeated theexperiment. He melted twenty-six grains of platinaupon a cupel, with sixteen times its weight of pure lead,which he had himself revived from litharge: the lead beingscorified, there remained in the cupel a button of platinaweighing twenty-one grains, so that the platina lost in thisoperation near a fifth part of its weight. From this ex-periment he conjectured, and not without probability con-sidering the little that was then known of the propertiesof this new metal, that a part of the platina was scorified'by the lead; that the whole might have been scorified by;repetitions of the process; and that consequently gold andsilver may be purified from platina, by cupellation withlarger quantities of lead than are commonly employed.What the author has modestly proposed only. as a con-jecture, to be confirmed or refuted by further trials, has bysome been taken for a certainty: in a letter presented tothe Royal Society soon after, the process is spoken of as amethod discovered by Dr. Brownrigg, for separating pla-tina from gold and silver. It is plain that this experimentmust have been made, and the author has lately informedme that it was, with the cast metal mentioned at the be-ginning of this history, which was then supposed to be trueplatina, and does lose of its weight in the common processof cupellation.

io. Mr. Scheffer tried the cupellation of the grains of

plctina with lead, and the event was exactly the fame as m

my