Page:Popular Science Monthly Volume 38.djvu/330

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and in its passage it was "sheared" or "slit" (hence the name "slitting-mill") into a number of bars or rods of the same width as the thickness of the cutters in use at the time. The shafts carrying the cutters could be taken from the frames or "housings" in which they revolved, and the cutters could be removed and replaced by others thicker or thinner as desired. The slitting-mill in Fig. 17 gets its motion from the same water-wheel shafts, E O, that drive the rolls C D.

John Houghton, in his Husbandry and Trade Improved, printed in 1697, speaks of rolling and slitting mills as "late improvements";[1] speaking of the operation of "slitting" iron bars that have been hammered out in a "blomary," he says: "They are put into a furnace to be heated red-hot to a good height, and then brought singly to the rollers, by which they are drawn even, and to a greater length; after this another workman takes them while hot, and puts them through the cutters, which are of divers sizes, and may be put on or off according to pleasure. Then another lays them straight, also while hot, and when cold binds them also into fagots, and then they are fit for sale."

By comparing this description of John Houghton's with Fig. 17, the original of which was published sixty-eight years later, it will be evident that very little change had taken place in the construction of slitting-mills in that period.

The furnace (whose door is seen at Y, in Fig. 17), in which the rough-hammered bars from the "blomary" were heated preparatory to rolling, was peculiarly constructed, and had fireboxes, P R, on each end. Sections of this furnace are shown in Fig. 18; No. 1 being a longitudinal vertical section through the fire-boxes, P R, and the reverberatory heating-chamber Q; No. 2 a vertical transverse section of the heating-chamber Q, the chimney q q, and its hood q. It will be observed that the chimney of this furnace is not placed, as in a modern iron heating-furnace, at one end of the heating-chamber, while the fire-box is at the other; but that it is located outside and in a measure detached from the body of the furnace, and that the products of the combustion of the wood (which was the only fuel used) burned

  1. The earliest publication known to me, in which the use of "rolls" for drawing and shaping metals is described, was written by Giovanni Branca. In his work, Le Machine (published at Rome in 1629), he gives a very curious illustration of a rolling-mill, which, notwithstanding its manifest absurdity, suffices to show that he understood the action of the "rolls" and their advantages. The next mention of the use of rolls for giving shape to metals passed between them is contained in a work by Vittorio Zonca, published at Padua in 1656. In this work Zonca gives an engraving and description of a mill for rolling the double grooved fillets of lead which were used for securing the glass in stained windows. We regret that our limited space prevents us from reproducing these illustrations, neither of which has ever been referred to in any history of the manufacture of metals.