V. Fufibility. 71 the crucible, which fhews they have a ftrong ac- tion on the argill or filex, or both. 2dly. With regard to barytes and calces of iron, I found them to adt on each other much more powerfully than limeand calces of iron : at 150% they melt in every proportion from 4 to 1 of either. Other proportions have not been tried. 3dly. As to magnefia and calces of iron, Mr. Achard found that, where the magnefia exceeds the calx of iron, they have no adlion on each other, at leaft at 150°, nor even when they are in equal quantities : but, when the calces of iron, exceed the magnefia as 4 to 1, they melt per- fedlly ; when only as 3 to 1, they melt leis per- fedtly; and when as 2 to 1, ftill lefs perfedtly. 4thly. With refpedt to argill and calces of iron, in my own experiments, when the argill exceeded the calces of iron, I obferved no tendency to fu- fion even in heats from 160° to 166 0 , nor even when they were in equal proportions 1 but, when the calces of iron exceeded the argill in the proportion of 4 to 3, or 2 to 1, the compound was fufible apparently in the fame proportion, that is, moft when 4 to 1, &c.; when I ufed ruft, i. e. femicalcined iron, the compound was greenifti. The heats from i56°to 160°. 5thly. As to filex and calces of iron, it appears, that they are infufible when the filex exceeds; but if the calces exceed, the compound will be fufible. Of