But early in the seventeenth century (1619) Dud Dudley, son of Lord Dudley, began to make use of sea and pit coal for smelting iron, and obtained a monopoly “of the mystery and art of smelting iron-ore, and of making the same into cast works or bars, in furnaces, with bellows.” Dudley sold this cast-iron at £12 a ton, and made a good profit out of it. He actually produced seven tons a week, which was considered a large supply, and shows the comparative insignificance of the industry then. However, it was only comparatively insignificant, for before the close of the century it was calculated that 180,000 tons of iron were produced in England yearly; and in the eighteenth century (1719) iron came third in the list of English manufactures, and the trade gave employment to 200,000 people. There was, however, still great {140} waste of wood, since a great many ironmasters did not use coal, and therefore the export and even the manufacture of iron was discouraged by legislation to such an extent that by 1740 the output had been reduced to 17,350 tons per annum, barely a tenth of the previous amount quoted. The waste of timber was most noticeable in the Sussex Wealden, the forests of which owe their destruction almost entirely to the iron and glass manufactures. But about this time another inventor, Darby, discovered the secret of the large blast furnace in which pit coal and charcoal were used. He began his experiments as early as 1730, but did not do much for some twenty years. In 1756, however, his works were “at the top pinnacle of prosperity; twenty and twenty-two tons per week sold off as fast as made, and profit enough.” After Darby came Smeaton, and other inventors, and the Industrial Revolution spread to the iron trade. We shall see it in operation in our next period.