586 



THE POPULAR SCIENCE MONTHLY. 



THE DEVELOPMENT OF AMERICAN INDUSTRIES 



SINCE COLUMBUS. 



IV. IRON-WORKING WITH MACHINE TOOLS. 



Br WILLIAM F. DUEFEE, Engineer. 



WHILE the builders and operators of blast-furnaces were 

 achieving such splendid results as have been described, the 

 owners, managers, and engineers of rolling-mills were not idle. At 

 the very beginning of rolling-mill construction in America the dis- 

 position to make improvements in known methods and to invent 

 entirely new mechanisms and processes was promptly manifested. 

 Even in the first mill of which we have any authentic account the 

 rolls and heating furnaces w T ere decided improvements on previous 

 practice ; and from that day to the present time the best Ameri- 

 can rolling-mill practice has been characterized by originality of 

 idea and perfection of construction. Fig. 41 is a longitudinal sec- 



Fig. 41. Longitudinal Section of a Heating Furnace. 



tion of a heating furnace in which coal was used as a fuel. The 

 " fire-box " with its grate is seen at the left ; to the right of this is 

 the " bridge-wall " separating the " heating chamber " from the 

 " fire-box." The bottom, a, of the "heating chamber" is made of 

 silicious sand. On the extreme right of the furnace is seen the 

 "cinder-tap," b, for the discharge of any liquid "cinder" made 

 during the operation of heating the iron ; near this " cinder-tap " 

 is the lower part of the " chimney-flue." The iron to be heated 

 was placed upon the sand bottom a, and the flame from the fuel 

 in the fire-box passed over it, not only heating the metal directly 

 but the roof and side walls and bottom of the heating chambei 

 also, which, as was said when this form of furnace was first intro- 



