STONE, ARTIFICIAL. The name given to various artificial compositions of which the basis is hydraulic cement, which are plastic when first made and assume with age a stone-like hardness and consistency. Some of these compositions possess undeniable merit for certain kinds of Work and are considerably used. The chief stones of this character are Bbton-Coignet, Portland stone, stone, Ransome stone, and Sorel stone. D0on-Coignct was invented by Coignet. a Frenchman. and as made by him was composed of Portland cement, siliceous hydraulic cement, and clean sand very thoroughly mixed with a small amount of cold water. This plastic mix ture is then placed in molds to harden for use. Portland stone is a mixture of Portland cement and sand or sand and gravel wet to make a plastic mixture and rammed into molds to harden. Under various trade names Portland stone has quite an extensive use in the United States. It is molded into blocks of numerous forms and sizes, with or without ornament, for buildings and other structures. Sand bricks are an artificial stone made by mixing sand and lime into a moist paste, molding this paste into bricks or blocks, and setting the molded blocks to harden in heated chambers. I/c.lfurtrie stone
is formed by adding alum and potash soap to the mixture for Portland stone. These ingredients form compounds of alumina in the pores of the stone, which reduce the capacity of the stone to absorb water and add somewhat to its strength. Ransom(' stone is made by mixing sand and sili cate of soda, molding the mixture into blocks or slabs, and setting them to harden under pressure in a hot solution of chloride of calcium. This material is used mostly in England, where it is applied to a variety of purposes. ,Norc/ stone is a French product. and is made by adding to oxide of magnesium a solution of chloride of magnesium. It is used mainly in making emery wheels. Consult Baker, Treatise on Masonry Construction (New York). Excellent articles on the manufacture of sand brick are contained in the Transactions of the American So ciety, VON. iv. and v. See CONCRETE; PAVEMENT.