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soon tarnished to a yellowish hue; the polished part grewdull but retained its colour.

3. A mixture of platina and copper of each one part,and eight of tin, proved softer than the foregoing, andflattened a little under the hammer. Broken, it shewed avery irregular surface, composed of a great number ofbright white plates. It did not polish well. The fracturesoon tarnished; the polished part retained its colour.

XIII. Platina with Iron.

1. Half an ounce of platina and an ounce of iron wirewere placed on a bed of gypsum in a Hessian crucible, andcovered and surrounded with more gypsum: after beingurged in a blast furnace with two pair of bellows for aboutan hour, the crucible was in great part vitrefied, and alarge hole made in its fide, by which most of the metal hadrun out. The experiment was four or five times repeated,but a perfect union of the platina and. iron could not beobtained, the crucible being corroded and vitrefied by thegypsum before the iron flowed thin enough to dissolve theplatina. It was observable that the iron, thus melted,proved very malleable; though some have thought thatforged iron, brought into fusion, is of the fame naturewith common cast iron.

2. Cast iron and platina, of each three ounces, exposedwithout addition to a strong fire, united into a thick fluid,which, on adding an ounce more of the iron, flowedpretty thin. The black lead crucible having become toosoft from the great heat, to admit of being lifted with thetongs, the metal was suffered to cool in it. On breakingit, the metal was found in one lump, not convex, but ofa very concave surface : its weight was about one sixteenthless than that of the platina and iron employed. It provedexcessively hard, so as not to be touched by the file, and

yet