138 TECHNOLOGY. 
Wrought-iron is produced immediately from the ore or from pig-iron; in 
the former case, where the blomary fire is made use of, the iron ore, roasted 
or not, is mixed with coals, and melted down upon an open hearth under a 
blast produced by bellows of the common form, or more generally by wooden 
cylinders urged by water-wheels. 
The production of wrought-iron from pig metal is accomplished in finery 
fires, or puddling furnaces. - In finery fires the metal is partially melted 
under the blast, and the carbon and foreign substances measurably expelled 
before it is taken to the squeezers. 
The puddling-furnace is undeniably the best adapted for converting pig- 
iron into bar-iron. The iron hearth of the furnace already described is 
covered to a depth of three or four inches with cinders from a charcoal 
forge, from another puddling-furnace, or from a re-heating-furnace. Ifnone 
of these can be obtained, cinder from a blast-furnace will answer. The 
furnace is then fired, and when the cinder is melted, and the bottom and 
sides are properly protected, cold cinder is thrown in; and when the bottom 
is so far cooled that the tools make no impression on it, the iron is charged. 
As the latter begins to get red it is turned and worked over, and as it 
becomes white and commences to melt, it is broken with hook-formed 
instruments, and mixed with the partially melted cinder; after a further 
heat it is divided into lumps twelve or fifteen inches in diameter, and carried 
to the hammer or squeezers. These lumps, called balls, are then subjected 
to the operation of shengling, which is performed under the hammer or in 
the squeezers, and which converts them into blooms or more regularly 
formed masses; these blooms then pass to the rough rollers. Sometimes no 
hammer or squeezers are employed, but the balls are taken directly from 
the puddling-furnace to the rollers. The roughing rollers take the bloom 
and reduce it into billets of a size proportioned to that of the bars to be 
drawn. ‘The rollers for the final preparation of the iron are seen in pl. 28, 
jigs. 12 a, 12 band 12c; fig. 18 represents them in plan; jigs. 14 and 15, 
cross-sections; jig. 16, the cog-wheel driving the rollers; jig. 17, a front 
view of a sheet-iron rolling machine; jig. 18, a view from above, and 
Jigs. 19 and 20, details of the same; fig. 21 shows the operation of roll- 
ing; and jig. 22, the cutting off of railroad rails by circular saws. The 
rollers are set in stroug cast-iron frames, and are adjustable more or less 
near each other by screws; they are furnished with round or angular grooves 
according to the size of iron to be rolled. 
After the balls are prepared in the puddling-furnace they are carried in 
the tongs (fig. 10) to the hammer, or, where no hammer is used, to the first 
set of rough rollers (figs. 12@ and 14), where they are drawn into billets 
or plates. The hammer is, however, to be preferred, as the cinder falls freer 
and the welding is more perfect. 
The iron thus prepared either by hammering or by passing many times 
through the rough rollers, is cut, bound into parcels, re-heated, and taken 
to the finishing rollers. 
Sheet-iron is made directly from the bloom upon the rollers (jigs. 17 and 
18), which are made to approach each other slightly after each passage of 
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