454 



THE POPULAR SCIENCE MONTHLY. 



front, built furnaces, as late as 1864, that, when measured by the 

 standard of the available knowledge of the time, were little better 

 than ponderous aggregations of ignorance and masonry. 



Among the earlier of the many improvements in the details of 

 blast-furnace construction and management, which were made in 

 consequence of the employment of mineral coal for smelting, was 



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Fig. 33. Vertical Section of a Charcoal Blast-Furnace. 



the substitution of blowing cylinders of iron for the wooden blow- 

 ing apparatus previously employed in connection with charcoal 

 furnaces. One of the simplest forms of iron blowing machinery 

 is shown in Fig. 34. This apparatus consisted of two vertical 

 "blowing cylinders," provided with appropriate valves, through 

 which the air was drawn in and discharged into a " wind-chest " 

 by the vertical reciprocation of a piston in each cylinder. These 

 pistons were actuated by the cranks on the gear-wheel shown, 

 through the intervention of suitable connecting-rods and walk- 

 ing-beams. The cut (Fig. 34) conveys only the simplest form of 



