of coarse sandstone; but the latter are covered with a lining of fire brick nine inches thick. The in-wall consists of two linings;

Fig. 64.

Anthracite furnace at Reading, Pa.

the interior is the lining which covers the boshes: outside of this is a space four inches wide, filled with coarse sand; and this is protected by a rough lining of slate, two feet thick. The rough walls of the stack are not heavy; but they are well secured by binders. b. Two furnaces lately erected at the Crane Works, near Allentown, may be considered the latest improvement. (Fig. 65.) The stack is thirty-five feet high; forty feet square at the base, and at the top thirty-three feet. This furnace is, therefore, but slightly tapered, and requires heavy stonework. It generates steam from the trunnel head gas flame. At most anthracite furnaces, this is done by putting the boilers on the top of the furnace. The hearth is five feet high, four feet square at the bottom, and six feet at the top; the inclination of the boshes is 75°, and the cylindrical part of the in-wall above the boshes is eight feet high, and twelve feet in diameter. From the cylindrical part up to the top, which is six feet in width, the in-wall runs in a straight line.

c. Fig. 66 represents one of Messrs. Reeves and Company's furnaces at Phoenixville, Pa. Its height is thirty-four feet. The hearth

Steam-boiler.

Fig. 65.

Section of an anthracite furnace at Allentown, Pa.

is six feet high, four feet three inches square at the bottom, and five

feet three inches at the top. The boshes. taper 68°, or at the rate of rather less than six inches to the foot. They measure thirteen feet at their widest part. Care should be taken that the lining and the boshes form a gradual curve, that sticking and scaffolding in the boshes may be obviated. The top of this furnace is eight feet square. There is no doubt that the form and construction of these anthracite furnaces have been carried, within the short space of a few years, to so high a state of perfection as to leave but little room for future improvements. Their shape is

worthy of imitation, particularly by

Fig. 66.

Western manufacturers, for coal Interior of an anthracite furnace

adapted to all of these furnaces is abundant in the West.

at Phoenixville, Pa.

The practical working of these furnaces will be explained elsewhere. We shall merely remark, in this place, that most of them generate the steam for the motive power of the blast, as well as the heat for the hot blast apparatus, at the top of the furnace. In this way, expense is not only saved, but a uniform generation of steam and heating of air are produced. In relation to the building of coke or stone coal furnaces, it is not necessary to enter into particulars, inasmuch as the principles applicable to these furnaces are applicable to charcoal furnaces. The cost of erecting such a furnace, it is almost impossible to state, for this will depend upon locality, material, wages, and individual tastes. But it may be laid down, as a general rule, that a stone coal furnace costs less than a coke furnace; and that, in most cases, a good charcoal stack can be altered so as to serve for stone coal.

In the Western States, many charcoal furnaces are in operation, and there is no limit to their extension, so far as raw material, wood, and ore are concerned. One circumstance, however, will necessitate the introduction of stone coal furnaces in the West; that is, the price of charcoal iron. Some localities can successfully compete against stone coal iron; but those which, besides enjoying that advantage, are situated near navigable streams or canals, are very few in number. We believe that the average cost of producing charcoal pig at Pittsburg is twenty dollars; some furnaces produce it at a cost of fifteen dollars. In as many cases, however, twenty-five dollars is paid for iron. The market price at Pittsburg has varied, for the last two years, from twenty-five to thirty dollars, according to quality. At this price, but little profit is left to the owners of the furnaces. How far the stone coal furnaces are in advance of this, will be shown by the following statement of the average result of three years' smelting. This statement has been furnished by Mr. Reeves, of Philadelphia:

AMOUNT OF MATERIAL CONSUMED TO PRODUCE ONE TON OF IRON AT ANTHRACITE FURNACE NO. 1, AT PHOENIXVILLE.

Iron ore
Anthracite coal

Limé

2.59 tons.

1.83 ton.

1.14 66

AMOUNT CONSUMED AT FURNACE NO. 2, AT THE SAME PLACE.

These furnaces smelt brown hematite, hydrated oxide of iron. If the Western iron manufacturers apply these numbers to their localities, they will find that the manufacture of cheap iron is perfectly in their power. The wages for producing one ton of anthracite iron, including incidental expenses, amount to two dollars and fifty cents; to which is to be added the interest on capital employed.

IX. The Management of Blast Furnaces.

We have already alluded to the practical management of blast furnaces; but in this place we shall examine the subject more extensively. After the rough walls of a furnace are completed, the lining and hearth are to be put in. Of the geometrical form of the hearth and in-wall we shall speak in another place, and at present confine our attention to the material of which they are made.

a. The chemical composition of the material of a lining is of little consequence to the manipulations, and to the results of the smelting process. A material sufficiently refractory to resist a moderate heat, but of such an aggregate form as to permit of frequent changes in temperature, is all that is needed. Of all the known native and artificial materials, none answers better than a well-made fire brick. Where fire bricks are very expensive, or where they cannot easily be procured, a stone in-wall may be put in; but the application of stone is restricted to charcoal furnaces, where well-roasted ores and high stacks are employed. In no other case can a stone or slate lining answer the purposes of a good in-wall; and even where employed through necessity, difficulties of a serious nature may be apprehended, such as the falling out of stones, or the caving in of whole parts. Any refractory sandstone, or, a still better material, silicious slate, will answer the purpose of such in-walls. Two or more concentric in-walls, one within the other, have no specific use. A second in-wall will be serviceable where the interior lining caves in, and where a continuance of the smelting operations is desirable. Such a lining, made of good slate, like that shown in Fig. 64, will answer every purpose.

b. The hearth is a very important part of a blast furnace. A variety of materials are used in its construction. In Sweden and Russia, granite, gneiss, or porphyry: in Austria, sandstone: in most of the furnaces of the Alpine Mountains, marble-at least in them the bottom stone is of marble: in Germany and France, limestone, marble, sandstone, fire brick, and cement: and in England and the

United States, sandstone. To make experiments on hearthstones, in our country, would be injudicious, for there is an abundance of serviceable material throughout the United States, from the beautiful kaolin of Connecticut, to the durable, coarse red sandstone of Arkansas; and as the tendency of our iron furnaces is to produce gray iron, as this ought to be their tendency, and as the ores in use are, almost without exception, oxides, there is hardly any choice left but to take sandstones. The coal fields afford almost every variety of sandstone; from the coarse, conglomerate, mill-stone grit, to the fine-grained, carburetted sandstone of Portsmouth, Ohio. Every one of these varieties is nearly everywhere accessible. No general tests of the refractory quality of the material in question can be given. The practical is the only test on which we can rely. Fire bricks have been tried, and, in some cases, with success; but it is doubtful whether fire brick will answer so well as good sandstone, particularly in stone coal furnaces.

c. After the lining and hearth are finished, fire may be kindled. This is to be done with great caution, to prevent cracking, or, what is worse, flying of the stones. It is advisable to wash a new lining and hearth, once or twice, with a composition of lime, clay, and common salt; this mixture will dry very hard, and, under a low heat, will readily melt into a very liquid slag, which glazes the whole interior. After fire is kindled, the tuyere holes should be closed, and the top covered by cast iron plates; this will prevent a strong draught, and a change of cold and hot air, which would be destructive both to hearth and lining. It is also advisable to cover the sandstones of the hearth with a four-inch lining of common brick, to prevent the direct action of the fire upon the stones. When the hearth and lining have been thus exposed to fire for a week or ten days, they will doubtless become tolerably dry; the hearth may then be filled with coal as high as the widest part of the boshes, and its temperature raised. But we should be cautious to keep the tuyeres shut, and to protect the timpstone either with a stopper of clay or a lining of brick. In filling coal we should proceed slowly; and no fresh coal should be applied until the flame rises through the last charge. The furnace may thus be heated within three or four days, if we are careful to keep the coal up, and to clean repeatedly below. But if time is not precious, the forehearth may be closed up, with the exception of a few small openings, with a brick stopper. This is to be taken out at least every twenty-four hours, and the hearth cleaned of ashes and clinkers.