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THREE:In the manufacture of iron a most material discovery of smelting the ore by the use of pit-coal was made. The forests of England were so much reduced by the consumption of wood in the iron furnaces, that it was contemplated removing the business to our American colonies. This necessity was obviated by the discovery by Dud Dudley of a mode of manufacturing bar-iron with coal instead of wood. This discovery had been patented in 1619, yet, singularly, had been neglected; but in 1740 the principle was applied at Coalbrookdale, and iron thus made tough or brittle, as was wished. Iron works, now not confined to one spot by the necessity of wood, sprang up at various places in England and Wales, and the great works at Rotherham were established in 1750, and the famous Carron works in Scotland in 1760. The quantity of pig-iron made in 1740 was calculated at 17,000 tons, and the number of people employed in the iron trade at the end of this period is supposed to be little short of 300,000.