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A feature of the last decade has been the appearance of wares which go to the extremes in what has been regarded as the usual raw materials of pottery. Formerly the chief chemical difference between pottery and glass lay in the low alumina content of the latter. But the fused silica ware containing 99 per cent, of silica, sand lime bricks which are 90 per cent, silica, 10 per cent, lime, siloxicon (a refractory compound of silicon, carbon and oxygen produced by heating ground coke, sand and saw- dust to 2600 C. in the electric furnace), and, on the other hand, the corundum and other alumina articles, suggest that the name Ceramics will have to include glass, pottery, cement, and all other manufactured articles containing either silica or alumina.* *Many precious stones pertain to the sphere of ceramics in regard to chemical com- position. Thus, amethyst and cairngorm are quartz silica, opal is hydrous silica. Corundum, ruby, sapphire, and Oriental amethyst are alumina. Turquoise is hydrous aluminium phosphate, and topaz aluminium fluosilicate. Magnesia and alumina form the spinel and ruby, and beryllia and alumina chrysoberyl and alexandrite. Zircon, jargoon, and hyacinth are zirconium silicate. Double silicates form a numerous class. Beryllium and aluminium form beryl, emerald, and aquamarine ; the garnets are silicates of aluminium with calcium magnesium or iron ; olivene and peridote are magnesium and iron, and sphene calcium titanium, silicates. 44 CERAMIC CHEMISTRY. Most of these new products result from the high temperatures possible in the electric furnace. They are generally shaped upon a core of carbon or similar material,