Semi-Steel

—If in the proce of puddling or decarbonizing cast iron the proce be stopped at a particular time, determined by indications given by the metal to an experienced eye, an iron is obtained of greater hardne and strength than ordinary iron, to which the name of semi-steel, or puddled steel, has been given. The principal difficulty in its manufacture is that of obtaining uniformity in the product, homogeneity and solidity throughout the entire ma . It is much improved by reheating and hammering under a heavy hammer; but it has not been found a reliable material for even cannon of small caliber. The celebrated guns made by Mr. Krupp of Germany are of cast steel, made from puddled steel, and of peculiar character, combining great tensile strength with the property of stretching to a great extent without breaking. Sir Joseph Whit worth improves the qualities of steel for his more recent guns by casting it under hydraulic pre ure.