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
Fig. 33.—Vertical Section of a Charcoal Blast-Furnace.
the substitution of blowing cylinders of iron for the wooden blowing 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 walking-beams. The cut (Fig. 34) conveys only the simplest form of
