AMERICAN INDUSTRIES SINCE COLUMBUS. 587 



duced, " reverberated " more heat upon the metal ; hence the name 

 " reverberatory furnace" often applied to such structures. The 

 walls, roof, fire-bridge, and chimney-flue are built of very refrac- 



Fig. 42. Levee Shears for cutting Bab Iron. 



tory brick, called " fire-brick." Furnaces of similar construction 

 (sometimes called "air-furnaces") are used for melting pig iron 

 for making heavy castings; but in these furnaces, instead of a 



Fig. 43. Front Elevation of Boiler-plate Shears. 



sand bottom of the form shown at a, the furnace at this part 

 has its bottom depressed so as to form a basin to hold the fluid 



