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chiefly platina. On grinding them together in an ironmortar, a freffi powder gradually separated, which, beingoccasionally washed off, in appearance greatly resembledthe foregoing, but was found, on proper trials, to partici-pate more largely of mercury and lead than of platina.The amalgam was of a very dull colour, and on being ex-posed to the fire in an iron ladle, swelled and leaped about,though the heat was scarcely sufficient to make any of thequicksilver evaporate. I therefore had the grinding con-tinued, in a kind of mill, composed of a thin iron plate,cut into the form of a cross, and made to turn in an ironmortar : the plate was bent up nearly to the shape of thebottom of the mortar, and between two of the ends wasfixed a piece of wood, the other two standing loose, andaccommodating themselves to the mortar in virtue of theirelasticity : the piece of wood received the end of an up-right spindle, which being secured by cross pieces to keepit in the middle of the mortar, and a small weight, some-times greater and sometimes less, placed on the top, awheel and pulley procured a rapid motion with little la-bour. After constant agitation in this machine, with wa-ter occasionally renewed, for seven or eight days, theamalgam looked bright and uniform, and suffered thequicksilver to exhale freely. The mercury being all eva-porated, there remained a dark grey powder, which provedupon examination to be platina with a very little lead.For a part of the powder being digested in aquafortis, asmall portion of it dissolved, and the solution appeared tobe no other than a solution of lead : the undiffolved part,now of a dark purplish colour, was mostly taken up byaqua regia, to which it communicated, not indeed thecommon hue of solutions of platina, but a kind of dullolive colour : plates of tin, however, quickly discoveredthat the matter dissolved was platina, by occasioning a pre-cipitate