USEFUL METALS 217 



rurible steel plants also manufacture annular hall bearings 

 largely demanded by automobiles. 



Electric-furnace steel is also manufactured in Syracuse and 

 largely used in springs, gears, shafts, steariiig knuekles, and all 

 important parts of automobile construction. It is estimated 

 that $3,000,000 is invested in the steel industry of the city and 

 that it stands second in the country in the quantity of its output 

 and first in quality of the steel manufactured. 



An ore to be of value at the present state of the iron industry 

 must occur in close proximity to a good market, must be of good 

 quality and large quantity, and must be favorably situated for 

 extraction and smelting. The most favorable location for such 

 a mine is: (1) Near good coking coal for fuel. (2) Near limestone 

 for a flux which should not contain more than 5 per cent, of mag- 

 nesium carbonate. (3) Where economical methods of trans- 

 portation exist. Unless these three requisites a e observed iron 

 ores cannot be extensively mined with profit save where the ore 

 is in great abundance and the most economical methods of trans- 

 portation exist. Iron is now so cheap that where mine operations 

 are difficult, as in deep mines, narrow veins, abundant gangue 

 minerals, and difficult transportation, it cannot be mined with 

 profit. There are enough good mines to make selection possible, 

 but the iron of the smaller mine may be obtained by electrolysis 

 which now bids fair to revolutionize the iron industry of the 

 world. 



The value of iron in the arts and industries depends upon the 

 fact that it is abundant and cheap; that by different processes 

 it can be made either brittle or malleable; soft, hard, or extremely 

 tough. The hardness is varied by heating and tempering. Sev- 

 eral metals such as chromium, nickel, molybdenum, titanium, 

 vanadium, tungsten and manganese render steel extremely hard 

 and tough. 



Pig iron is converted into steel on account of the superiority 

 of steel for structural purposes, and the ever-cheapening proc- 

 esses of its manufacture. Large engines, locomotives, cars, etc., 

 are now made of steel rather than cast iron because of its superior 

 strength and resistance. 



Three countries, the United States, United Kingdon, and 

 Germany produce more than three-fourths of the pig iron of the 

 world and likewise approximately four-fifths of the world's pro- 

 duction of steel. The United States alone produces more than 



