in our misdirected zeal to save expenses, we put up an imperfect blast machine, we shall find that every dollar saved will be counterbalanced one hundredfold by losses in the furnace.

The application of blast in the furnace deserves investigation in every instance. We will notice some leading points; but these are not presented as infallible rules. Soft and weak charcoal cannot bear strong blast, and a pressure of from half a pound to five-eighths of a pound to a square inch, may be considered sufficient; strong blast would be likely to choke the furnace above the tuyere, by depositing charcoal dust in the boshes. Strong, coarse charcoal will bear a pressure of from three-quarters of a pound to one pound. A weaker blast is very apt to be troublesome, besides using more coal, and producing white metal. Ore, considered as an oxide of iron, free from foreign matter, has no relation whatever to the quality of the blast; but it is different with ore considered as a mixture of oxide of iron and foreign matter. The kind of blast that should be applied depends very much on the fusibility of the foreign matter. But this question we shall discuss in another place. The form of the interior of the blast furnace is of considerable importance. A high, narrow hearth requires stronger blast than a furnace without a hearth, or a furnace with a low hearth; but the width of the top, in proportion to the diameter of the boshes, is of more importance than the quality or pressure of the blast. It may be laid down as a rule, that the larger the throat, in proportion to the boshes, the stronger ought to be the blast; and that a narrow top and wide boshes, while they permit a weaker blast, involve the loss of much fuel.

The air introduced by the blast machine into une furnace should be as dry as possible. The main reason that blast furnaces do not work so well during summer and clear warm weather, as during winter, and cold, rainy days in summer, is, that a large amount of watery vapors is mixed with the atmospheric air in hot weather. This water is very injurious in a furnace, as we shall hereafter see. To keep the air dry, the blast machine should be erected at the coldest and driest spot we can possibly select. We should take especial care that it is not exposed to the hot air around the furnace, and that it is beyond the reach of the steam-engine; for the air will be more moist around the engine and the heated furnace than anywhere else. The best means of making a furnace work well during summer would be to put the blast machine in an ice-cellar.

Hot blast may be, under some circumstances, advantageous; but

in others, it is decidedly injurious. It is, at best, a questionable improvement; and it may be doubted whether the manufacture of bar iron has derived any benefit from it; qualitatively, it has not. Hot blast is quite a help to imperfect workmen. It melts refractory ores, and delivers good foundry metal with facility. The furnace should be carried on for three or four weeks with cold blast, that the hearth and lining should be heated thoroughly before the application of hot air.

The quantity of air required to be blown into a stack depends on the quantity of metal produced in the furnace. But there is a limit to the amount which the furnace produces; if we attempt to exceed that limit, loss, instead of gain, is the consequence. A narrow top, high stack, soft coal, and imperfectly roasted ores, require quantitatively more blast than where opposite conditions exist; but the blast must be weak. A wide throat, low stack, hard coal, and ores well roasted, require stronger pressure but a less volume of blast. The changing of nozzles and tuyeres is, therefore, a matter of considerable importance, and the effect of this change should be clearly appreciated before it is attempted.

The manner in which stock should be hoisted and delivered at the trunnel head, is a question of economy. If the digging of a yard is very expensive, and if the cost of stone walls and a trunnel head bridge cannot well be borne, coal and ore may be hoisted on an inclined plane, by means of the blast-engine, or by water or horse power. But, under all circumstances, there should be a bridge house, sufficiently large to receive the night stock, and where possible, also the Sunday's stock. To the coal and ore yard the manager should pay particular attention. The coal, after being unloaded, must, in every case, be left twenty-four hours in the yard before it is stacked in the coal houses, for it very often happens that coal will rekindle, even though two or three days have elapsed since it was drawn from the pits. Soft and bad coal should be mixed with the old stock, and immediately used; it is useless to store soft coal, for it will crumble to dust. Braise, which is not used for the burning of ore, or at the timp, must be saved, for it is an excellent fuel for the burning of lime. Iron rakes, for drawing coal, are commonly in use; but they are very destructive to charcoal, and should be avoided in the yard. Wooden rakes are preferable. Charcoal exposed to the influence of the weather during the summer season suffers but little in quality; but snow and frost are very in

jurious. If we expect good work in the furnace, all the coal must be stored under roof before frost sets in.

At a charcoal furnace, particularly where the stacks are small, great attention is to be paid to the roasting, breaking, and cleaning of the ore. Iron is revived with difficulty from imperfectly roasted ores, especially if the stacks are low, or of small capacity. In this case, the ore arrives at the tuyere in an unprepared state. The hearth is thus left to do most of the work; but this it is unable to do; the consequence is that, even from good-natured ores, bad, or at least white iron, of inferior quality, waste of stock, and frequent disturbance in the regular work, will be the result. From low stacks, and from small stacks, we cannot expect anything like fair work, unless the ores are well roasted. Well roasted ores are of a red or brown color; they adhere like dry clay to the tongue, and are easily broken. Where ores are roasted so hard as to melt into a clinker, they are as bad as though they were not roasted at all; in fact, they may be considered worse, for such ores cannot fail to work badly; while raw ores can frequently be used with but little injury. The breaking of ores is a matter of great importance: ore that is too coarse is injurious; under some circumstances, so is coal that is too fine. A narrow top will work to greater advantage with small, than with coarse ores; and a wide throat requires uniform ore of not too small a size. This rule holds good in all cases. Experience has clearly proved that loose, soft, mouldy, and small ores do not work so well in a furnace with a wide top, as in a furnace with a narrow top; and the reverse is the case with hard, solid, and dry ores, such as the specular, magnetic, and spathic kind. If the ores are brought in a clean state to the yard, and if the roasting is done by wood and small charcoal, but little cleaning is needed; but if brought in an unclean state, and if stone coal or any mineral is used for roasting, they should be carefully cleaned from the adhering dust. In every instance, a careful roasting of the ores at charcoal furnaces will prove advantageous; this is the surest means of saving coal and blast, and of avoiding many annoyances in the working of the furnace. Even if we are not particular as to the quality of the metal; even if we are satisfied with white or mottled iron, the advantages of well roasted ores are so great, economically considered, that too much attention cannot be paid to this branch of the yard operations.

Of fluxes, and the mixing of different kinds of ore, we shall speak at the close of the chapter. But as this is a subject of the

greatest importance; as on this depend the well-being and success of blast furnace operations, it will not be inappropriate in this place to call the attention of the furnace manager to it. The application of proper fluxes, or the mixing of ores and fluxes, is not only the basis of success, but by this branch of the manager's duty the quality and the price of the metal are determined. It has been proved by experience that the great difference in the amount of fuel consumed, varying from one hundred bushels to three and even four hundred bushels of charcoal to the ton of iron, chiefly depends upon the composition of the cinders or slag: besides this, the quality of the metal is regularly improved by applying the proper fluxes. Some previous knowledge of the elements of chemistry is required to enable one fully to understand this subject; but we shall endeavor to make it comprehensible, without employing scientific terms or technical phrases.

The working of a charcoal furnace is not difficult, if coal, ore, blast, and stack are in good order. The first cast, after starting a furnace, is generally taken on the second or third day; it is advisable not to tap too soon, for there is little or no danger in delay. A well-filled crucible for the first cast removes all the adhering cold clinkers in the lower parts of the hearth; heats the hearth thoroughly; and gives a fair chance, even good prospects, to the following casts. If, however, the bottom is too cold, so that the iron congeals on touching it, we should be cautious not to let too much iron accumulate in the hearth; but we should tap frequently, and make every effort to produce gray iron, by which alone cold iron, sticking in the bottom, will be removed. If the hearth is cold, if the ores are too refractory, or if, through other circumstances, clinkers or cold cinders accumulate in the hearth, the furnace should be frequently opened, and these obstructions removed. This object, however, should be effected with expedition; otherwise, the withdrawal of the blast will leave the hearth too cool. If cold lumps of cinder are allowed to accumulate, they will by degrees reach above the tuyeres, and thus the furnace operations will be exposed to the greatest danger; for, if no coal intervenes between these cinders and the blast, the hearth is very soon cooled to such a degree that the descending iron and cinder, thus rapidly increasing, would finally bring the operation to an entire close, and compel a scraping of the materials out of the furnace. If strange or very refractory ores are to be smelted, it is advisable to lay the tuyeres six or seven inches above the timpstone, that the keeper may be enabled to

reach with ease above them, and remove any obstructions which may there accumulate. The space between the dam and timp is very easily kept tight by a good stopper made of common clay mixed with sand. The burning out of a timp is a very disagreeable occurrence. To prevent this, various means have been devised. We shall allude to one, that which is commonly called the water-timp. This is a cast iron pipe, six or seven inches square, with a round bore of from one and a half to two inches in diameter. This timp is laid across the forehearth, below the timpstone, and kept cool by a constant current of cold water. This is a very convenient method of saving the timpstone, and of preventing the stopper from being blown out; but it has several disadvantages. It keeps the hearth cool, and tends to diminish burden and yield; and, what is a still greater disadvantage, it tends to chill the cinders of refractory ores; these cinders, when cooled, accumulate so fast, that they frequently compromise the safety of the furnace operations. We have tried this experiment, and have found it to answer exceedingly well where ores, well fluxed, were smelted; but we have found it accompanied with difficulty and danger where-in addition to the presence of a strong cinder-strong iron, inclined to white, was manufactured. Where bog ores are smelted, and where a wide hearth is in use, we would recommend the water-timp; but in scarcely any other case will it afford any advantage.

VI. Coke Furnaces.

But few blast furnaces work coke in this country, and even these, so far as we know, are not in operation at the present time; at least, that is the case with the two largest establishments of this kind, Mount Savage in Maryland, and the Great Western Iron Works in Pennsylvania. That coke furnaces cannot prosper on the eastern side of the Alleghany Mountains is not strange, for against the anthracite furnaces they cannot successfully compete; but how it happens that coke furnaces cannot prosper in the Western States, is more than we are able to comprehend. Some experiments have been made in Clarion county, Pa., and some in Ohio, with raw coal, which, we understand, have succeeded exceedingly well; but the demand for pig metal is very limited in the western markets, and hence the small difference in the price offered is not a sufficient inducement to substitute it for the charcoal iron at present in general use for foundry purposes. Such small experiments will doubtless be succeeded by experiments on a larger scale. The use of raw