English: ... The furnace of cementation in which bar iron is converted into blistered steel is represented in fig. G17, 618, 619. It is rectangular, and covered in by a semicircular arch, in the centre of which there is a circular hole left, 12 inches diameter, which is opened when the furnace is cooling. It contains two chests called "pots" c, c, made either of fire-stone or fire-bricks; each "pot" is 3 feet wide, 3 feet deep, and 12 feet long. One is placed on one side, and the other on the contrary side of the fire-grate, a b, which occupies the whole length of the furnace, and is 13 to 14 feet long; the grate is 15 to 16 inches broad, and the bars rest from 10 to 12 inches below the inferior plane or bottom level of the " pots ;" the height of the arch at the centre is 5 1/2 feet above the top of the " pots," the bottoms of which are nearly level with the ground, so that the burs of iron do not need lifting so high when charging them into the iurnace. The flame rises between the two " pots ;" it passes also below and around them, through the horizontal and vertical flues, d, and issues from the furnace through the six small chimneys, H, into a large conical space which is built around the whole furnace, 80 to 40 feet high, open at the top. This cone increases the draft of the furnace, and carries away the Smoke. There are three openings in the front of the arch ; two, T, fig. 619, above the pots, serve to admit and remove the bars ; they are about 8 inches square ; in each a piece of iron is placed upon which the bars slide in and out of the furnace. The workman enters by the middle opening, P, to arrange the bars, which he lays flat in the pots, and spreads a layer of charcoal, ground small, between each layer ; the bars are laid near each other, excepting those next to the side of the pot, which are placed an inch from it ; the last stratum of iron is covered with a thick layer of charcoal, and the whole is carefully covered with loamy earth 4 to 5 inches thick. The iron is gradually heated, in about 4 days has become fully heated through, and the furnace has then attained its maximum heat, which is maintained for 2 or 3 days until the first test bar is drawn out ; the heat is afterward regulated, according to the degree of hardness which may be required. The iron is converted in 8 days if for soft steel, and in 9 to 11 days if for harder purposes.