after the introduction of the Bessemer ( 1855) and Thomas ( 1879) processes. After the middle of the century, too, people were still quite content to dress iron in the decorative forms of past styles. But even then there were architects and engineers who visualized new possibilities and anticipated many of the later solutions in their buildings and projects.

7b. Crude early furnace. Built on a hill-side. Wind supplied draught. After eighth century replaced by small shaft furnace with bellows, which made higher temperatures possible and yielded more ron. 7a. Smelting furnace of the ancient Egyptians. who probably acquired their knowledge of "the wonder of heaven" from meteorites.

Iron as a multi-purpose material has been known for nearly five thousand years,
as discoveries in Mesopotamia and Egypt prove [

Attempts to use pit-coal instead of wood failed at first. But Abraham Darby, after
earlier attempts by Dud Dudley ( 1621), succeeded in 1713 in partially substituting
coal for charcoal. His son carried this process further, using -- as is still custo-
mary to-day -- coke in place of natural coal. In contrast to wood, coal was widely
available, and iron could, therefore, be produced in greater quantities. Thus was
laid one of the essential foundations of the Industrial Revolution in England.
Manpower could be replaced by the machine.

The coke-processed pig-iron, however, was inordinately brittle, unmalleable and
of little practical use. For this reason it had to be subjected to further treatment in

8. Section through coke blast-furnace, end eight-
eenth century. Fuel is now coke instead of char-
coal. Temperature of iron raised to smelting point.
Pig-iron obtained in molten form, instead of pasty
lumps (blast furnace smelting since fourteenth
century). To produce wrought (malleable) iron,
a refining process was necessary, for which char-
coal was still needed.

9. Section through puddling-furnace. Invented in
England, end eighteenth century: refinement
now possible with coke. Fuel and ore no longer in
immediate contact. A hot draught of air is carried
through the reverberatory furnace, in which the
liquid pig-iron was "puddled" (stirred) to prevent
formation of slag. Later replaced by the Bessemer Converter
( 1855).

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