made of fire-bricks, and which does not extend to the bottom of the hearth. The horizontal dotted line, (h, fig. 2,) shows the level to which the smelted materials can rise before running over the damstone (d) at c, where the cinder will escape first, being the lightest, whilst the smelted iron occupies the bottom. To prevent the fluid matter from being forced out by the blast, clay is rammed beneath the temp, around the twiers, and upon the surface, at h, where it is retained by heavy iron plates, which are raised every few hours, to allow the cinder to run off along the level of the top of the dust-plate c, i, whilst the metal is run off every twelve hours, at the lower level of d, through an aperture at the bottom of the dam-stone. The dam-stone is defended in front by a large iron dam-plate (de, fig. 1) against which the dust-plate c, i, rests. The lower edge of the latter rests upon the ground, which is raised to about the level of the bottom of the hearth d, e.

"Fig. 2 would represent a transverse section of the stack, if the left half were symmetrical with the right. In this case the temp m, and the open space in front of it would be filled with stone to the bottom of the hearth, and e would represent the place of exit for the iron.

"The bosh BB, fig. 2, (shaded vertically,) resembles a large funnel except that its termination at H, fig. 1, 2, is square. It is built of fire bricks, except its lower portion in front, where, in consequence of the open temp arch (m), a large stone (n) called the sconsh'n, is laid across the front portion of the hearth. The inclination of the bosh is seen to be at a higher angle than when charcoal is used; but it may vary considerably without affecting the result. When in blast a few months, the bosh increases in steepness from the abrasion of its surface, and the hearth partakes of this enlargement; so that instead of being a parallelogram, it assumes an oval form. The enlargement of the hearth continues until its walls become so thin, that the radiation of the heat will prevent the inner portion from melting away any further; and in case the temperature diminishes, the inside will be protected by a coating of slag. I have known a furnace to be in successful action, when the hearth had been so much enlarged as to have the middle portion of the inmost back sow (8, fig. 2) melted away, permitting the blast to escape until the aperture was closed with tenacious clay. In this case the under surface of the sow was in contact with the brick wall usually built beneath, as an additional barrier to the escape of the heat.

"Towards the head of the furnace, there are three equidistant apertures (f, fig. 2) to admit the waste flame, first under the boilers, then through a return flue in them into a hot oven, which is placed in part upon the top of the stack posteriorily and laterally. When a separate engine is employed, the oven is placed upon the front side of the top, and the flame passes into it by a single aperture.

"The boilers are in this case three in number, twenty-six feet long, forty-five inches in diameter, with a return flue eighteen inches in diameter. They are represented as w w, in fig. 3, where the course of the flame is represented by the arrows leaving the outlet of the flues in the stack, and passing beneath and through the boilers into the hot oven o, which has one or two high chimneys to secure a proper draft. For the purpose of exhibiting the position of the boilers, a part only of the brickwork which supports and encloses them is represented in the figure and the minor details of construction are omitted. Figure (3) is an elevation and partial section of the right side of fig. 1, 2, showing a twier arch, with the aperture for the admission of the blast, the parapet upon the top, and the chimney (2) around the tunnel-head. The engine* is placed upon the ground on this side, the boilers extending to the bank against which the structure stands. When the convenience of a bank or hill cannot be had, it is evident that both the boilers and oven might be placed on

The engine is of 100 horse power, and the diameter of the furnace 10 feet. It is capable of smelting 90 tons a week.

or near the ground, if the chimney were sufficiently high, (not less than seventy feet,) and the walls built so as to be free from crevices.

"The boilers are supported on large iron beams, (partly shown below the bricks at x,) between which arches are turned in their longitudinal direction. There are several doors in the position of x, to allow the flues to be cleared from ashes, &c. These doors open into the arches beneath, and there are others along the sides for the. same purpose. The boilers are usually placed in contact with the oven; but the passage y (which extends to the chimneys) is proposed to be left to turn more or less of the flame into the chimneys, which will place the relative distribution of the heat to the oven and boilers under control, a point which seems not to have been hitherto attained. This might also be accomplished by separate chimneys to the oven and boilers. In either case, the chimneys must be supplied with a damper, which is best placed upon the top.

"If four simple boilers were used, the flame might be passed under one pair and return under the other; or the oven might be placed upon the bank, which would afford a good foundation for it and its chimneys; but the distance which the heated blast would be required to travel before reaching the twiers, would be an objection.

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Fig. 4.

b

b

"The hot-oven is built and arched over with brick, and strongly bound externally with iron, the heat being sufficient to destroy supports passing through it. It is sufficiently large to contain a small forest of upright flattened pipes about ten feet high, with an internal cavity of about four by seven or eight inches, the thickness of the metal being about an inch. These are maintained at a red heat, the blast through them preventing their destruction. They stand upon two large pipes or cylinders about a foot in diameter, and from twelve to fifteen feet long, with a single row of apertures, (a, d, fig. 4,) and one or more (b, c) large enough to admit of a double row of apertures. Over the neck of each aperture a detached collar is placed, into which a pipe is firmly cemented, and the heads of two pipes on adjoining cylinders are similarly connected by an auxiliary pipe forming a semicircular or gothic arch, as represented in section in the upper part of the figure. The blast entering the first cylinder at a, meets a partition near the middle, and has to pass through the seven openings and pipes across the arched heads into b, and so on to d d, when it passes in the opposite direction to its place of exit at g, 9 j whence it descends to the twiers. The partitions are

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not in the middle of the cylinders, because by the time the air has passed half through them, it requires more room on account of its expansion." H.

WIRE CABLES.

Wire ropes or cables adopted in mining shafts and on inclined. planes, in preference to hempen ropes.

It does not appear that the use of wire cables in the hard anthracite collieries of Schuylkill county, has been altogether successful as a substitute for hempen rope in the "slopes." The difficulty arises from the chafing of the cables, and the clogging of the rollers by fragments of anthracite, which injure the wire cables much more rapidly than it does the hempen ropes.

We annex some valuable information on the subject of Iron Wire cables, taken from the Foreign portion of the first edition.

Employment of Iron Wire Cables in the coal pits where steam engines are used.

M. le Bergmeister Klotz has published a note in the "Archiv für Mineralogie," which article has been translated by M. Ch. Combes.

The translator states that twisted iron wire cables have been introduced in the shafts of extraction in the mines of the Hartz. The economy in the costs of extraction resulting from these wire cables, compared with those formerly made of hemp, soon determined the engineers and proprietors of the mines of Saxony, of Prussia, and

almost all Germany, to adopt them. In France they have been slow to follow this example. The economical details, very circumstantially presented in M. Klotz's notice, appear to call for the attention of proprietors of mines, and of manufacturers of wire, in all countries; and we present the readers of this volume with some valuable practical results, obtained under the supervision of the Prussian mining engineers, which are, probably, perfectly new to them.

Hempen Cables.-Towards the close of the year 1833, the providing and maintenance of the "cables of extraction," in several of the collieries in the district of Essen and Werden, in Prussia, were given to the enterprise and competition of the manufacturers of hempen ropes; their remuneration consisting of a price agreed on for each 100 scheffel [ = 147.9 English bushels] of coal extracted from the mine, or shaft.

The names of those collieries, their depth of shaft, and the prices paid for the service of those hempen cables, are as follows:

=

= 147.9

That of Saelzer, whose vertical shaft is 216 Engl. feet deep, and that of Neue Aack, which is 308 feet, Engl. deep, paying fr. 0.3608 3d. (three pence halfpenny) $0.07 per 100 scheffel [= Engl. bushels] about five tons. These terms are equivalent to of one penny Engl. or $0.01 American currency, per ton, as cost or service of the hempen cables.

=

=

The colliery of Wische, for a vertical shaft of 81 lachters 152.604 metres [= 500 English feet,] paying fr. 0.4638 [ = 4.494d. $0.09] per each hundred scheffels. This is equivalent to ths of one penny, or $0.01% per ton, for use of the ropes.

=

That of the Kuntswerk, whose shaft is 46 lachter = 152.6 metres 283 Engl. feet,] paying 2 silbergros 6 pfennigs

=

16

=

fr. 0.3092 3 pence Engl.$0.06 American,] per 100 scheffels. This charge is equivalent to of a penny or $0.01 per ton. Subsequently, the price was lowered, in this case, 2d. English, = $0.04 per 100 scheffels. Therefore the payment for the use of the hempen ropes was reduced to 44 of a penny, or $0.00.88 per ton. But, it is added, at this last price, the contractor of cables suffered a loss, which he was able to prove.

100

The colliery of Braut in Küpers wiese has had for several years a contract which still subsists, by which it pays for the extraction of each 100 scheffels, by an inclined shaft, of 39 lachter [240 feet,] 3.596d. Engl. 7% cents. This sum is equal to 0.719d. $0.01, per ton.

=

44

Without following M. Klotz through the details of the comparative value, weight, durability, cost, and power of the wire cables, at all the shafts, we will select the first only, the colliery of

Salzer and Neue Aack.

1. Results with the hempen cables.-In 1833, two cables were placed in these shafts, which lasted six months and fourteen days.