PORCELAIN-JASPER. Varieties, according to Link, melt before the blowpipe into a white glass. Constituent Parts. Silica, Alumina, Magnesia, Oxide of iron, Potass, According to Rose. Geognostic Situation. It Is always found along with burnt-clay and earth-slags, in places where pseudo-volcanoes have formerly burnt, or where beds of coal are now in a state ot inflammation. Hence it follows, that it is a pseudo-volcanic production; and according to Werner, it is slate-clay converted into a kind of porcelain by the action of the heat of the vol cano. As the coal wastes, hollows are foimed in the bed, and the superincumbent porcelain-jasper breaks in pieces, and falls into them: hence it never occurs in re gular beds, but in irregular broken masses, intermixed with burnt-clay, earth-slags, and similar substances. Geographic Situation. Porcelain-jasper occurs in Bohemia, principally in the plain betwixt the Krzgebirge and the Mittelgebirge, where immense beds of coal appear. It also occurs at I’lanitz, near Zwickau in Saxony, and in the neighbour hood of Zittau in Upper I.usatia. Likewise at Lrterode, at the Meisner, in the llabichtswald; at Dutweilci, in the department of Snare ; and also in Iceland. o Fourth 60.75 27.25 3.00 2.50 3.66