There is another kind of best iron, distinguished by the name of "scrap-iron," being made up of all the scraps, short lengths, ends cut off the finished bars, as before explained, and all the little bits of wrought iron that can be collected together. Of these there is always a considerable quantity accumulating in an iron work; the larger pieces are made up into piles, and the smaller into balls. The piles may be heated to a welding heat, and rolled at once into finished bars, but the balls, consisting of smaller pieces, are shingled under the great hammer, to consolidate them and bring them into the form of a bloom. This bloom is reheated, and when rolled, produces excellent tough iron, superior to the piled scraps that have not been shingled. Scrap-iron, thus reworked, often produces so excellent a quality, as to fail under the denomination of the next described quality of iron, namely, Best-best Iron, No. 3, Chain-cable Iron. - These names, and various others intended to denote the superlative degree, are given by manufacturers to that kind of iron which is deemed to be, in reality, of the best quality, prepared with mineral coal.
This metal is chiefly manufactured for the purpose of enabling it to resist most effectually a longitudinal strain or tension; and the property is best acquired by the careful selection of the best materials, and repeatedly cutting, piling, shingling, and rolling, as before explained. In the preparation of this superlative quality of iron, the utmost attention to the process is necessary; and any bloom or bar that may be incidentally injured in its tenacity should be rejected by the manufacturer, whose reputation might be injured by such iron receiving the mark that properly belongs only to the primest quality. It is this kind of iron which is chiefly employed in the making of chain-cables, in tie-rods and bolts, that are subjected to a powerful strain.