ASME-Landmark:Cornwall Iron Furnace

From its inception, Cornwall occupied a special position among Pennsylvania's iron furnaces. It owes its existence to the Cornwall Ore Banks a few miles south of Lebanon, a deposit of rich magnetite ore that, until development of the Lake Superior deposits, was one of the most valuable iron-ore bodies in the U.S. It had been discovered in 1734 by Peter Grubb, who built a blast furnace in 1742.

The stone-built blast furnace was typical for its time, producing about 20 tons of pig-iron and cast-iron products a week. It was a squat stone stack 20-feet square at the base and 11 at the top, with a height of 31 feet. The blast air was provided by a pair of wood-and-leather bellows nearly 21 feet long driven by an overshot water wheel. The furnace was open at the top, and the measured batches of ore, charcoal fuel, and limestone were charged in, more or less continuously, simply by being dumped into the opening by wheelbarrow. After the blast was stopped and the liquid slag run off, the dam then was further lowered and the iron, pooled at the very bottom of the furnace, ran out into the molds prepared in the floor of the casting house.

A major reconstruction in 1856 to 1857 produced important changes: the furnace itself was enlarged; the blast-air bellows were replaced by a pair of wooden cylinder "blowing tubs"; the waterwheel that had powered them was replaced by a 20-horsepower steam engine; and a pair of waste-heat boilers to supply the engine was built into the open stack of the furnace. See ASME website for more information