14. Every preparation having been made, the furnace is gradually heated with charcoal, and by degrees filled to the top, when a small quantity of the ore is thrown on, and the blast is applied at the bottom near the hearth. The blast is supplied by means of one or two cylindrical bellows, the piston of which is moved by steam or water power. 15. The coal is measured in baskets, holding about one bushel and a half, and the ore, in boxes holding about one peck. Six baskets of coal, and as many boxes of ore as the furnace can carry, is called a _half charge_, which is renewed as it may be necessary to keep the furnace full. With every charge is also thrown in one box of limestone. 16. The limestone is used as a flux, to aid in the fusion of the ore, and to separate its earthy portions from the iron. The iron sinks by its specific gravity, to the bottom of the hearth, and the earthy portions, now converted into glass by the action of the limestone and heat, also sink, and float upon the liquid iron. This scum, or, as it is usually called, scoria, slag, or cinder, is occasionally removed by instruments made for the purpose. 17. When the hearth has become full of iron, the metal is let out, at one corner of it, into a bed of sand, called a _pig-bed_, which is from twenty to thirty feet in length, and five or six in width. One concave channel, called _the sow_, extends the whole length of the bed, from which forty or fifty smaller ones, called _pig-moulds_, extend at right angles. The metal, when cast in these moulds, is called _pig-iron_, and the masses of iron, _pigs_. 18. _Pig-iron_, or, as it is sometimes called, _crude iron_, being saturated with carbon and oxygen, and containing also a portion of scoria, is too brittle for any other purpose than castings. Many of these, such as stoves, grates, mill-irons, plough-irons, and kitchen utensils, are commonly manufactured at blast furnaces, and in many cases nearly all the iron is used for these purposes. In such cases, the metal is taken in a liquid state, from the hearth, in ladles. 19. In Great Britain and Ireland, and perhaps in some other parts of Europe, iron-ore is smelted with _coke_, a fuel which bears the same relation to pit-coal, that charcoal does to wood. It is obtained by heating or baking the coal in a sort of oven or kiln, by which it becomes charred. During the process, a sort of bituminous tar is disengaged from it, which is carefully preserved, and applied to many useful purposes. THE IRON-FOUNDER.