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7° Fufibility. 16 magnefia *3 ruft of iron * calx 41 filex 16 calx *7.5 magnefia 17,5 calx of iron Jiornblendc, by my änalyfis, melted into a black compadt glafs at 136*. hornhlendc of Wiegleb melted at '137° into a greenilh black glafs. Corollaries. Hence it follows, i, that all binary combina- tions of the five earths are infufible, and in every proportion, under 166 0 , except two : ift, Calx and Silex, in equal parts, and in a heat not under 150°, and in that only into an enamel; and, 2dly, filex and barytes : Thefe appear to aff on each other in a heat not below 150°, where the filex is to the barytes in the proportion of 3 to 1, or 2 to 1, or the barytes to the filex in the proportion of 4 to 3, or a to 1, but fcarcely when they were in equal quantities. 2. With refpeft to calces of iron and the 5 fimple earths, vve may obferve, firft, that where the lime exceeds the calx of iron even in the pro portion of 9 to 1, it is fo far affe&ed by it as to be converted into a porcelain in a heat of 150°, and then begins to afl on the argill or filex of the crucible. When the lime is in the proportion of 4 to 3, or 2 to 1, the compound is yet more fufible, but ftill only into a porcelain : yet Mr. Achard found it to cryftallize, which argues a farther degree of fufion. But if the calces of iron exceed the lime in the proportion of 4 to 3, or 2 to 1, the com- pounds are ftill more fufible, and pafs through the