THE NONMETALLIC MINEBALS. 249 



into the furnace; and to this quantity is afterwards added from 660 to 

 1,100 pounds of wrought-iron scrap as soon as the melting is com- 

 plete. When a suitable temperature is attained the slag is run off, 

 and the next charge is introduced into the furnace when the bath is 

 quiescent. A sample is then taken and tested by bending, and if it be 

 found that the percentage of phosphorus is too high, more lime, or 

 lime and iron scale, are added, as much being introduced as the bath 

 will take, and the addition of ferro-manganese is also made. 



The iron chromate is decomposed only under the influence exerted 

 by the reagents and oxidizing alkaline substances. Heat alone is 

 insufficient to decompose chromate of iron, which may float in a bath 

 of molten steel covered with basic slag without dissolving. One of 

 the principal conditions of success in the employment of the chrome 

 ore lining consists in carefully picking the pieces of ore used, which 

 should be of uniform composition; and the best composition of ore 

 used for lining reverberatory furnaces is found to be from 36 to 40 

 per cent of chromic oxide, 18 to 22 per cent of clay, 9 to 10 per cent 

 of magnesia, and at most 5 per cent of silica. 1 



The total annual product of American mines does not exceed between 

 3,000 and 4,000 tons, valued at the mines in California at not more 

 than $8 a ton for 50 per cent ore. Delivered in Baltimore its value 

 is from $20 to $25 a ton. 



Some 4,000 tons are annually imported. The chief foreign sources 

 are Russia, New Zealand, New Caledonia, and Australia. 



The following notes relative to the chrome industry in America are 

 of sufficient interest to warrant reprinting here: 2 



The chrome industry is one of the most unique and characteristic in Baltimore. 

 It originated in the early discovery of chrome ore in the serpentine of Maryland, and 

 has ever since maintained its prestige as one of the sources of the world's supply of 

 the chromates of potassium and sodium, which have many applications in the arts. 

 The following is the substance of an historical account of the Maryland chrome 

 industry, kindly prepared by Mr. William Glenn: 



In 1827 chrome ore was first discovered in America on land belonging to Mr. Isaac 

 Tyson, in what are known as the Bare Hills, 6 miles north of Baltimore. Mr. Tyson's 

 son, Isaac Tyson, jr., then in business with his father, was persuaded by an English 

 workman to attempt the manufacture of "chrome yellow" from this material, and 

 this was done in a factory on what is now Columbia avenue, in Baltimore, in 1828. 

 In the year of the discovery of the Bare Hill ore, Mr. Isaac Tyson, jr., who seems to 

 have possessed a very keen power of observation, as well as a considerable knowledge 

 of chemistry, recognized in a dull black stone, which he saw supporting a cider barrel 

 in Belair market, more of the same valuable material. Inquiry disclosed the fact 

 that this had been brought from near Jarrettsville, in Harford County, where much 

 more like it was to be found. Mr. Tyson at once examined the locality, and finding it 

 covered with boulders worth $100 a ton in Liverpool, purchased a considerable area. 



1 Journal of the Iron and Steel Institute, 1895, pp. 506, 507. Abstract from L'Echo 

 des Mines, XXI, p. 584. 



2 From Maryland, Its Eesources, Industries, and Institutions, Baltimore, 1892, pp. 

 120-122. 



