i. Nails are an important article of commerce, and an item in our factories which must be regarded with due attention. For these, good iron is unnecessary; they require neither strength nor the quality of welding, which are two requisites of iron the most difficult, at least the most expensive, to produce. Nail iron must be malleable, that is, in one direction, and as cheap as possible. Sheet iron, which is now most generally employed in the making of nail plates, is ill adapted to make a cheap, and, at the same time, a good nail. So long as good charcoal iron is used, the quality of sheet iron is secured: but, if an inferior quality of charcoal blooms, or puddled iron, is employed, the form of the sheet iron does not answer so well; the nails will be cold-short, though made from an article which, for the manufacture of bar iron, would be highly useful. In New England, nail plates from four to six inches wide, and from ten to thirty feet long, are made. These are preferable to sheet iron; that is, where the quality of iron is the same, a far better nail can be made from these plates than from broad plates or sheet iron. As previously stated, we are enabled to make fibrous and very malleable iron from almost any kind of pig iron, whatever its quality may be, provided there is no necessity of making the iron very cohesive, or of giving it the property of welding in the blacksmith's forge. Such iron is made in the puddling furnace by a very low heat, and it must be reheated at the lowest possible. temperature; otherwise, it will lose its fibres and malleability, and become cold-short. It cannot be transformed into sheet iron at all; but it will make a hoop very malleable lengthwise, though not transversely to the fibres. It cannot resist a long-continued red heat, which is frequently applied at the nail machines, without altering its fibrous into a cold-short texture. Such iron, if well worked, is generally very soft; it may be cut when cold, and then tempered so as to give color after the cutting of the nails. This is a proposition, however, not based upon practice, and requires confirmation. Iron of this kind can be made from pig iron, no matter how bad its quality may be. Puddling does not at all improve its purity; it only alters its texture from a granulated into a fibrous aggregation. Of all kinds of iron it is the cheapest, for it is worked fast, with but little loss, and little fuel; no skill is required to manufacture it. Industrious work and the lowest possible heat are the best means of success in puddling. Such iron is of but little use for other purposes, but we verily believe it will make a nail far superior to most of the nails at present in market.

To make nails from white, coarse, fibrous iron, however strong it may be, is unprofitable, for the nails will split, and cut badly. Such iron is of too good a quality, and is better adapted for making coarse bar or heavy sheet iron. Whatever may be the kind of iron used for making nails, it is always better to draw it into long and small nail plates; these are to be cut into strips crosswise, so that the nail can be cut parallel with the length of the plate and fibres. The piles for making nail plates are to be put together with due regard to the production of the most perfect fibres. All cross piling is to be avoided; and if cold-short iron is to be worked at all, it must be mixed regularly in alternate courses with fibrous iron. Such piles may be very heavy; the greater the number of cuttings of rough bar, the better will be the result. The rolling of these piles is to be performed in such a manner as to make the welding joints parallel with the surface of the nail plate. In the reheating furnace, the lowest heat commensurate with the performance of the operations is the most profitable. Any heat relatively too high will transform most kinds of fibrous iron, particularly this, into cold-short iron, or iron of a crystaline texture. In the technical management of a rolling mill, we cannot pay too much attention to the classification of the puddled bars, and the composition of the piles, before they enter the reheating furnace.

CHAPTER VI.

BLAST MACHINES.

THE principles involved in the construction and application of blast machines are based rather upon the chemical effect which a strong peculiar draught produces in burning fuel, than on any mechanical or chemico-physical effect. The latter effect merely increases the consumption of fuel in a given space, and increases the heat in that space to a limited degree; but the former causes a union of the oxygen in the blast with the fuel or carbon in a manner more or less favorable to the reviving of iron from the ore, and the protection of the iron against oxidation.

The means to effect a favorable result in the application of fuel for the purpose of augmenting temperature, as in puddling and reheating furnaces, and heating stoves, are various. This result can be accomplished by the simple application of chimneys, or of blast, or by using both together. Fuel is most perfectly used where it is oxidized in the highest degree; this oxidation takes place in the reheating furnace, where, generally, all the hydrogen is converted into water, and all the carbon into carbonic acid. We cannot say the same of any other apparatus, for we generally find a mixture of carbonic oxide, carbonic acid, and free oxygen, which is an evidence of imperfect combustion. Increased draught, or the concentration of more heat in the fire chamber, will lessen such an evil; but there is frequently a deficiency of draught in cases in which heat is necessary, as in that of the puddling furnace. If, in such instances, it is impossible to produce sufficient heat by the draught of the chimney, we are compelled to make use of blast machines. This is the case with anthracite coal and coke. How chimneys act in producing draught, and what are the rules to be applied in constructing them, are matters which require scientific demonstration not included in our investigations. We have described the practical workings and dimensions of apparatus, which may be deemed sufficient for all practical purposes. An explanation as to

the chemical effect of blast under different pressures, we shall give at the close of the chapter.

There are many forms of blast machines; but in our own country we are very fortunately reduced to the most simple and practical. We shall notice some blast machines in operation in Europe, which are frequently recommended by writers on metallurgy, principally for the purpose of showing their imperfections. The most simple blast machine is the smith's bellows, a description of which it is unnecessary to give.

I. Wooden Bellows of the Common Form.

A kind of blast machine, called Widholm's bellows, is very extensively used in Sweden, Russia, Germany, and France. We do not know that any are employed in the United States. As it works well, as the expense of its construction is small, and its application to the Catalan forge very simple, we shall furnish a drawing and description of it. Fig. 131 shows it in section; a is the

movable part or piston; b an iron rod connected with a crank of the waterwheel, or the steam-engine; c, c are the valves, and d the nozzle. The latter is fastened to the permanent top f, which is again fastened to some wooden framework. The whole has the appearance of a common smith's bellows, with the only difference. that it is made entirely of wood. From ten to twelve strokes may be made in a minute, and two bellows are required for one fire. The whole is from six to seven feet long and thirty inches widethe piston having a motion of twelve inches. This kind of machine is applied to no other apparatus than the charcoal forge, and we allude to it merely because it is simple and cheap, fulfilling its purpose excellently.

II. Wooden Cylinder Bellows.

These are of various forms. We have seen square cylinders and round ones: the piston playing from the top, or from below; or the piston working in both directions. There are vertical and horizontal cylinders, and machines working with one, two, or three cylinders, with a dry receiver, water receiver, or with no receiver.

In our own country, we are almost entirely confined to one principal form, that is, the machine with two round tubs or bellowsthe piston working from below, and a dry receiver placed on the top of the tubs. This may be considered the best form of the wooden blast machine, if but a single stroke is desired. Fig. 132 is a representation of a blast machine of this kind; a, a are the bellows;

b the receiver from which the sheet iron pipe c leads the blast to the furnace; d, d are the pistons, moved alternately by the beam