212. This is a reverberatory furnace of great length, the hearth being about one hundred feet long by five to eight feet wide. It is traversed lengthwise by plows and scrapers attached to endless chains, which, passing over rollers at the ends of the furnace, carry the plows back to the place of entrance, where the ore is fed in continuously by a mechanical arrangement. By the action of the plows the ore is not only turned over, but is also progressed gradually towards the hottest part of the furnace, thence to a cooling hearth, and is finally discharged into a suitable receptacle. In a furnace of this size several fires are used on each side, at different points in the length. A great advantage of this furnace is, that very little of the ore is carried to the flues by the draft. It can be operated by one man on a shift, and has a capacity of as much as 40 tons per 24 hours. By a recent improvement the furnace is built in two stories.