only. This process, known as “puddling,” consists in withdrawing the carbon which had mixed with the iron during the process of smelting, and opened a wholly new field for the production of English iron. Smelting furnaces were built fifty times larger than before, the process of smelting was simplified by the introduction of hot blasts, and iron could thus be produced so cheaply that a multitude of objects which had before been made of stone or wood were now made of iron.
In 1788 , Thomas Paine, the famous democrat, built in Yorkshire the first iron bridge, which was followed by a great number of others, so that now nearly all bridges, especially for railroad traffic, are built of cast-iron, while in London itself a bridge across the Thames, the Southwark bridge, has been built of this material. Iron pillars, supports for machinery, etc. , are universally used, and since the introduction of gas-lighting and railroads, new outlets for English iron products are opened. Nails and screws gradually came to be made by machinery. Huntsman, a Sheffielder, discovered in 1790 a method for casting steel, by which much labour was saved, and the production of wholly new cheap goods rendered practicable; and through the greater purity of the material placed at its disposal, and the more perfect tools, new machinery and minute division of labour, the metal trade of England now first attained importance. The population of Birmingham grew from 73,000 in 1801 to 200,000 in 1844 ; that of Sheffield from 46,000 in 1801 to 110,000 in 1844 , and the consumption of coal in the latter city alone reached in 1836 , 515,000 tons. In 1805 there were exported 4,300 tons of iron products and 4,600 tons of pig-iron; in 1834 , 16,200 tons of iron products and 107,000 tons of pig-iron, while the whole iron product reaching in 1740 but 17,000 tons, had risen in 1834 to nearly 700,000 tons. The smelting of pig-iron alone consumes yearly more than 3,000,000 tons of coal, and the importance which coal mining has attained in the course of the last 60 years can scarcely be conceived. All the English and Scotch deposits are now worked, and the mines of Northumberland and Durham alone yield annually more than