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ing of this history, and that what he melted with goldwas the true platina; in which cafe, the gravity of pla-tina being supposed 17, the increase of gravity on mixturecomes out about a twentieth part, so that about a tenthpart of the platina has its bulk lost in the mass.

To satisfy myself in this point, I weighed hydrostaticallythe mixture, already mentioned, of equal parts of platinaand gold. The specific gravity of the gold was 19,285 :the platina was the larger grains, whose gravity, as we haveseen in the first section, was at least 17. The compoundweighed in air 13605, and lost in water 750, whence itsgravity was 18,140: the gravity by calculation comes out18,071 ; so that though the platinas gravity had been nomore than 17, the increase of gravity from the mixturewas not very considerable. As a little loss had happenedin the fusion of this mixture, and as the specific weight ofthe platina employed was not certainly known, I made twofresh ones, with pieces cut off from the same mass of gold,and some of the largest grains of platina, whose gravitywas nearly 18. One of these mixtures, weighing 5129,lost in water 276 ; and the other,weighing 6415, lost 34.-5 j.whence the specific gravity of the former turns out 18,583,and that of the latter 18,594, which come as near to oneanother as can well be expected in experiments of thiskind : the gravity by calculation is 18,622 ; so that both.mixtures were a little specifically lighter, or expanded in-to a larger volume, than if the metals had been weighedseparately, or joined by simple apposition of parts. Asthese experiments were made with a good deal of care,it may be presumed that in those, where there seemed to-be a great increase os gravity, or contraction of volume,either some error happened in the weighing, or the platinaIjctd not been all taken- up by the gold in the fusion.

L weighed.