Page:Popular Science Monthly Volume 73.djvu/318

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POPULAR SCIENCE MONTHLY

PSM V73 D318 Longitudinal and transverse views of the power generating plants.png

Longitudinal and Transverse Views of Power Houses, showing wheelpits, generators, shafts, turbines, penstocks and discharge tunnels.

that of carborundum in 1891 by Mr. Edward G. Acheson is of great practical value. This new product is made by chemically combining in the intense heat of an electric furnace of the resistance type common sand and ground coke. After the charge has remained in the furnace for about thirty-six hours in a temperature of over 7,000° Fahrenheit, the resulting combination is found in a beautiful crystalline form. Carborundum ranks next to the diamond in hardness and is therefore used as an abrasive. In its so-called amorphous form it is used as a substance of great refractory power.

Metallic silicon, which is largely used in the steel industry to absorb the gases of the molten steel, is made at Niagara Falls by a deoxidation or reduction process. Ordinary sand and ground coke are intimately mixed and subjected to the heat of an electric furnace. The carbon combining with the oxygen of the sand is evolved as carbon monoxide gas; the residue is the element silicon in almost chemically pure condition.

Another of Mr. Acheson's useful discoveries is the production of graphite by artificial means. Graphite is carbon, but not the only form of carbon. Carbon exists in the amorphous form as in coal,