, Fiifibtlily. 73 3. If the filex exceeds, a porcelain may be produced in feveral inftances, and a glafs in one, namely, when they are in the proportion of 3 filex, 2 magnefia, and 1 argili. ♦ Argill, Calx, and Silex. 1. If the calx exceeds, either a glafs, a porce lain, or an infufible mafs, may arife, according to the proportion. 2. If the argill exceeds, a porcelain may in many cafes be obtained, bot not a glafs. 3. But if the filex exceeds, a porcelain or ena- , mel is frequently obtainable, probablv alfo a glafs, for the heats I tried were not very high. Of Cakes of Iron. Compounds, t'nat owe their fufibility to calces of iron, havc always the appearance of a flagg. SEC-