The fine metal, obtained in the manner we have described, is next broken into pieces, and subjected to heat in a reverberatory furnace. A rapid heat is given at first to liquefy the iron, and is then diminished by means of dampers; the melted mass is violently stirred to expose it to the action of air and heat, by which the carbon is burnt away, and a part of the oxides of iron and the earthy bases combined and vitrified; as the carbon is separated, the metal gradually loses its liquidity, and finally dries, or assumes the consistence of sand: this shows that the carbon is separated, and the iron has assumed its malleable nature. The addition of water aids the oxidation of the several substances, and facilitates the process. The heat is again increased, and the metal collected under it, and rolled together into parcels suited to the action of the drawing machinery, and to the size of the bar that is to be made; these are pressed together, and a partial union takes place among their particles. When they have attained a white heat, they are withdrawn in succession. In some cases, where the number of puddling furnaces is great, they are immediately carried to the rollers and drawn down. But where quality is more regarded than quantity, they are first subjected to the action of the hammer, and finally rolled. The latter process has the advantage of separating more completely the vitrefied oxides, than can be done by rolling alone, but it will often require a second heat, which is given in a forge fire called the _chaffery_. When rollers are used alone, a minute and half is sufficient to form the bar; and a power of thirty houses will roll two hundred tons per week.