448 



Introduction to the Study of Science 



coal, a tough steel point hard enough to wear well. Tempering 

 by this method of observing temperature is limited to the range 

 between 392 F. and 572 F. The table gives the important 

 facts. 



The color remaining upon steel after being tempered may 

 be removed by polishing. Tempered tools of all sorts are 

 usually polished enough to destroy all signs of the " temper 

 colors." Occasionally a tool may be found which has blue 

 markings, though these may be artificially produced. 



218. Uses of steel ingots. The general outline, page 440, 

 shows the chief uses of steel ingots, the product of steel making. 

 The rolling mills, steel foundries and forges, wire, rod, and 

 nail mills, the structural shape, rail, pipe, -and tube manufactures, 

 to name only a few of the many auxiliaries which convert steel 

 into finished products, indicate generally the extent and magni- 

 tude of the iron and steel industry of our country, and at the 

 same time the main uses to which steel is put. 



