HEARTH FOR REFINING PIG IRON. A, a flat hearth, covered with sand or loam, and surrounded with metal troughs, B, through which a stream of water is constantly flowing, to keep the sides from melting; C, are the tuyeres in connection with the blowing-engine. BLAST FURNACE. CATALAN FORGE. PUDDLING FURNACE. A, the hearth; F. the grate or fireplace; C, the chimney with a damper at the summit to regulate the draught; D, a bridge separating the grate from the hearth, for preventing the direct contact of the fuel with the iron.