7. Several moulders work together in one foundery, and, when they have completed a sufficient number of moulds, they fill them with the liquid metal. The metal for small articles is dipped from the hearth or crucible of the furnace with iron ladles defended on every side with a thin coating of clay mortar, and poured thence into the moulds. But in casting articles requiring a great amount of iron, such as cannon, and some parts of the machinery for steam engines, the iron is transferred to the moulds, in a continued stream, through a channel leading from the bottom of the crucible. In such cases, the moulds are constructed in a pit dug in the earth near the furnace. Large ladles full of iron are, in some founderies, emptied into the moulds by the aid of huge cranes.

8. Although the moulders have their distinct work to perform, yet they often assist each other in lifting heavy flasks, and in all cases, in filling the moulds. The latter operation is very laborious; but the exertion is continued but a short time, since the moulds, constructed during a whole day, can be filled in ten or fifteen minutes.

9. Iron-founderies are usually located in or near large cities or towns, and are supplied with crude iron, or pig metal, from the blast furnaces in the interior. The metal is fused either with charcoal or with pit coal. In the former case, an artificial blast is necessary to ignite the fuel; but in the latter, this object is often effected in air furnaces, which are so constructed that a sufficient current of air is obtained directly from the atmosphere.

10. The practice of making castings of iron is comparatively modern; those of the ancients were made of brass, and other alloys of copper. Until the beginning of the last century, iron was but little applied in this way. This use of it, however, has extended so rapidly, that cast iron is now the material of almost every kind of machinery, as well as that of innumerable implements of common application. Even bridges and rail-roads have been constructed of cast iron.

THE BAR IRON MAKER.

1. Bar-iron is manufactured from pig-iron, from blooms, and directly from the ore; the process is consequently varied in conformity with the state of the material on which it is commenced.

2. In producing bar-iron from pigs, the latter are melted in a furnace similar to a smith's forge, with a sloping cavity ten or twelve inches below, where the blast-pipe is admitted. This hearth is filled with charcoal and dross, or scoria; and upon these is laid the metal and more coal. After the coal has become well ignited, the blast is applied. The iron soon begins to melt, and as it liquefies, it runs into the cavity or hearth below. Here, being out of the reach of the blast, it soon becomes solid.

3. It is then taken out, and fused again in the same manner, and afterwards a third time. After the third heat, when the iron has become solid enough to bear beating, it is slightly hammered with a sledge, to free it from the adhering scoria. It is then returned to the furnace; but, being placed out of the reach of the blast, it soon becomes sufficiently compact to bear the tilt-hammer.

4. With this instrument, the iron is beaten, until the mass has been considerably extended, when it is cut into several pieces, which, by repeated beating and forging, are extended into bars, as we see them for sale. The tilt-hammer weighs from six to twelve hundred pounds, and is most commonly moved by water power.

5. For manufacturing bar-iron directly from the ore, the furnace is similar in its construction to the one just described, and the operations throughout are very similar. A fire is first made upon the hearth with charcoal; and, when the fuel has become well ignited, a quantity of ore is thrown upon it, and the ore and the fuel are renewed as occasion may require. As the iron melts, and separates from the earthy portions of the ore, it sinks to the bottom of the hearth. The scoria is let off occasionally, through holes made for the purpose. When iron enough has accumulated to make a loop, as the mass is called, it is taken out, and forged into bars under the tilt-hammer.