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I weighed also hydrostatically the other mixtures of pla-tina and gold, and sundry mixtures of it with differentproportions of the other metals. Such masses as couldbear the hammer, were gently hammered a little, withcare not to make them crack; for the pure metals them-selves, after fusion, are seldom sound to come up to theirtrue specific weight, till brought to greater solidity underthe hammer. The surface was filed smooth, where anycavities or irregularities were likely to retain air; and mostof them were kept immersed in water for an hour or more,that the air might be more effectually extricated, and thewater more closely applied to them. The effect of thisprecaution was manifest in some trials purposely made;when the metal, hanging in water from the end of thebeam, had been cleared from all visible air bubbles, andexactly counterpoised; on standing for an hour or two, itsensibly, and sometimes very considerably preponderated.The water was in some of the trials melted snow, and inothers distilled water, which were both found to be of thelame specific weight. The temperature of the air, wasfrom the 50th to the 60th degree of Fahrenheits thermo-meter.

The balance, made use of in these experiments, was ofgreat sensibility, but not exactly equibrachial : and here itmay be proper to observe, that though the writers on.ba-lances require, and are very solicitous about procuring, a.perfect equality of the arms; yet as this equality is ex-ceeding difficult, if not impossible, to be obtained, so nei-ther does it appear anywise necessary to the accuracy of theinstrument- If ten equal small weights,.put into one scale,,are counterpoised by a weight in the other; and if theten weights be then removed, and a bit of silver or brassplate put in their room; it is evident, that when thisplate shall; be made equiponderant to the. counterpoise, it

will