The Birmingham age-herald., 1902-10-19
of lesa nroftablv as road material, rail-

of less profitably as road material, rail- road ballast and in land reclamation.
 The most important of the uses or slag is in the manufacture of structural materials, especially in the manufacture of hydraulic cements. Slag cement is pro-
 duced by pulverizing, without calclna-
 tion, mixture of granulated basic blast
 furnace slag and slaked lime. This pro- duct, although really a pozzuolanic ce- ment, Is usually marketed as Portland cement" in spite of differing from true Portland cement in manufacture, com position and properties, six or eight plants are at present engaged in manu- featuring slag cement in the United States, the production for 1901 being 272, 6S9 barrels As slags cooled slowly are only feebly hydraulic, the stag used in the manufacture of slag cement must be cooled suddenly as possible.
 This is done by bringing the slag, as it Issues from the furnace, in contact with a jet of cold water This granulat es the slag. renders 1t strongly hydraulic and removes most of the sulphur. True Portland cements can be made from mixtures of which one element is blast furnace slag, in which case the slag Is ground, intimately mixed with powdered limestone, and the mixture then calcined and reground. Two plants are engaged Tn the InanuIacIuTe or fOTlldllQ Ctiicill from slag and limestone in the United States. In England, blast-furnace slag has been somewhat largely employed as an adulterant of Portland cement.
 The highly phosphatic slags produced by basic Bessemer converters are valu- able fertilizers, and in Germany especially large quantities are annually sold under the name of Thomas silcate. These phos- phate slags are more efficient as fertiliz- are hor 1n f11fnarQ1 uhnsnhafpG The slight development of the basic Bessemer steel industry in the United States neces- sarily renders the use of these phosphatic slags of less commercial importance than In Europe During 1901 about 1000 tons of phosphate slags produced in the United States were sold as fertilizers. This American material has been tested by the American agricultural experiment sta tion. which reports that slag phosphates gave a greater total yield than did any of the other insoluble phosphates. The slags produced in steel plants using the open hearth process are less valuable as fer tilizer than those produced by basic Bes- semer converters, as they contain less phosphoric acid and more silica and lime than the basic Bessemer slags.
 Over half the material marketed as ssmineral wool' or "silicate cotton is de- rived from slag, the remainder being manufactured from natural rocks Of sev- eral different types. During 1901 about
 $500 tons of mineral wool were made from slags in the United States. The most im- portant property of slag wool from commercial point of view is that 1t is
 very poor conductor of heat which prop
 erty renders 1t valuable for all uses Tor
 which a non-conductor is desirable, as
 steam pipe coverings, safe Things, etc.
 Slag has been utilized in the manufac- -ture of paint rock, in the preparation or alum and, in small quantities, in the man. ufacture of inferior grades of glass.
 About 5000 tons of slag were sold in 1901 in the United States for use in construct ing macadam highways and for railroad ballast. Sections of roads constructed in New Jersey with sag macadam, under state supervision. have proved entirely satisfactory. Slag has been used in high way construction to some extent near Buffalo, N. Y, to a greater extent in Pennsylvania and Alabama, and most ex- tensively in the counties of Baltimore, Howard and Prince George, Maryland, where under certain conditions, 1t has been found a highly satisfactory road material In several states, notably in Alabama. slag is largely used as rail- road ballast. Large quantities of slag are also used for retaining land and filling abandoned mine workings.