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those mixtures Were kept. On weighing them hydrosta-tically, the more spongy ones were found nearly as ponde-rous as the crude platina. Among the more compact, thegravity of one turned out 19,083, that of another 19,136,and of a third 19,240. It is probable that these remark-able gravities proceeded partly from the platina havingbeen purified in the process from its lighter heterogeneousadmixtures, and partly from an increase of gravity occa-sioned by the coalition of the platina with the lead. Thelast of these mixtures, whose gravity was 19,240, is thatwhich was melted with equal its weight of gold, as men-tioned in page 548.

6. A mixture of one part of platina and three of goldwas cupelled with lead in an assay furnace. The matterworked well for a considerable time: at length it collecteditself into a bright hemispherical lump, which by degreesbecame flatter, dull coloured, and rough. The button, onbeing weighed, was found to retain about a twelfth part oflead.

7. The experiment being repeated with a mixture ofone part of platina and six of gold, some part of the leadappeared still to be retained. The bead proved rounderand brighter than the foregoing, and of a good golden co-lour on the outside; but it broke easily under the hammer,and appeared internally greyish : some of the fragmentshung together by the outward golden coat.

8. Mixtures of platina and silver, submitted to the com-mon process of cupellation, retained likewise a little ofthe lead. These, in becoming consistent, formed not he-mispherical beads, but flat masses, very rough and brittle,and of a dull grey colour both externally and internally.

9. The cupellation of platina with lead was one of theexperiments made by Mr. Wood, and communicated tothe Royal Society in the year 1750; but the platina being

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