Page:Popular Science Monthly Volume 38.djvu/175

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163
AMERICAN INDUSTRIES SINCE COLUMBUS.

either by the "trompe" or by wooden or leather bellows; and sometimes by what some writers—in utter defiance of Euclid and all his disciples—have called "square wooden cylinders," worked by rude water-wheels.

The ores most frequently reduced in these "blomary fires" were the rich magnetites containing about seventy per cent of iron, although poorer ores could be, and oftentimes were, used. Sometimes the ore was employed in the "raw state" (i. e., just as

PSM V38 D175 A blomary fire.jpg
Fig. 10.—A Blomary Fire.

it is taken from the mine), but the best practice was to subject it to a preliminary roasting in heaps. The operation of smelting the ore, or more properly deoxidizing it (for the metallic iron obtained in these "fires" was not the result of a true fusion), was substantially as follows, viz.: The bottom and sides of the "hearth" having been lined with a thick coating of charcoal dust, it was then filled with charcoal, upon which crushed ore was thrown, and kept in place by a dam of charcoal dust (c, Fig. 10). The fire was blown gently at first, and as the heat increased a more powerful blast was employed; ore and coal were