Green red beech, charred shortly after being cut,

66

Dry red beech and oak, of two years' standing,

oak,

66

peeled, 23.0

0.3

24.0 0.3

peeled, 25.7 0.3

Green white oak, charred three months after being cut, 22.4 0.3

"peeled, 21.2 0.3

Red beech and oak, cut in January, and charred in

August,

23.4 0.5 0.3 66 13.5 0.4

Green red beech, charred immediately after being cut, 12.9

66

We thus see that one hundred pounds of wood in kilns produce, on an average, twenty pounds of charcoal. In retorts and ovens, the amount seldom exceeds twenty-two pounds. The advantage, therefore, of employing ovens, apart from other considerations, is not great; but this is the ground of preference. Ovens are advantageous where wood can be transported on water; this transportation charcoal cannot bear without injury. Charcoal absorbs water and gases in large quantities; and what it gains in specific gravity it loses in combustibility; still, it is generally preferable for making iron. On what hypothesis this anomaly is to be explained, we are unable to say. We simply mention it as an established fact. Charcoal will absorb a large amount of water within the first twentyfour hours; but, after that time, very little. Different kinds of charcoal absorb water in different quantities, to wit:

Charcoal from lignum vitæ gained 9.6 per cent.

13.0

66

That water cannot be the cause of improvement, is evident. To assist those who desire to investigate this subject, we subjoin a table on the absorption of gases by charcoal within the first twentyfour hours after charring. One hundred parts of charcoal absorbed

i. Many iron manufacturers desire to realize the products of distillation; but the deficiency in the quality of the charcoal more than counterbalances the whole gain of the distillation. The iron master will employ his time far more profitably by cultivating the charring for the production of charcoal alone.

k. The time best adapted for charring, in the woods, is from May till October, inclusive. During the summer, the air is bland, the roads good, and the furnace yard dry; considerations of great importance. The price of charcoal varies, in Pennsylvania and the neighboring States, from four to six cents per bushel of five pecks, if bought in the yard. Managers ought to examine closely the specific gravity of the coal before buying, for slowly charred coal is generally twenty per cent. lighter than properly charred hard coal, made from the same wood. A bushel of five pecks, or 2675 cubic inches, of fresh charcoal, made of beech, oak, maple, and hickory, ought to weigh from fifteen to sixteen pounds; a bushel of pine coal, from ten to eleven pounds; and the prices paid for charcoal should vary accordingly. The wages of colliers for charring vary from one dollar twelve and a half to one dollar and twentyfive cents per one hundred bushels; colliers to pay their hands, to have the loan of tools, to have the wood delivered at the level, and leaves. From seasoned wood the yield ought to be forty bushels per cord; the loss charged to the collier. At this rate, the collier should be permitted to form his own judgment whether the wood is correctly ranked. If found deficient, a liberal deduction should be granted. If the collier is expected to furnish a given yield, a prompt attendance of the teams is required, that he may not sustain loss through delay in hauling. All necessary roads must be made by the employer. From ten to twenty cents, according to locality, is paid for the hauling of wood to the levels.

VI. Charring of Turf.

The charring of turf is far more easily effected than the charring of wood, partly on account of its square form, partly on account of

its chemical composition. In pits, the charring of turf is not difficult, if we pursue the same method as that pursued in the charring of wood; but we are forced to leave channels, or draft-holes, in the kiln, because the square pieces pack so closely, that, without this precaution, sufficient draft would not be left to conduct the fire. Turf is generally found in considerable masses in one spot; therefore the erection of char-ovens is no object of mere speculation, but affords all the advantages of a permanent establishment. Char-ovens for turf are comparatively small, and of course not expensive. We therefore shall omit a description of charring in pits, and shall proceed to describe a char-oven, which has been in use for more than ten years, and consequently sufficiently tested. Fig. 32 represents

a vertical cylinder, built of bricks, with a round cupola on the top; it is nine feet high, and five feet and a half in diameter, which gives 250 cubic feet capacity. The inner cylinder b, built of fire brick, is surrounded by a mantel a of common brick, and the space left between both is filled with sand. Sometimes a brick d runs all the way through, to bind both walls; on the top is a round opening e;

e is an iron plate to close the draft-hole c; ƒ is a board, or a piece of sheet iron, to hold the sand, which is used to shut the air out, by filling the space g. The turf is filled in at c, and packed closely, with the exception of a few channels at the bottom, which correspond with the little draft-holes h, h, h. A vertical chimney is left in the centre, at which gases may escape. The fire is put in through c, down to the bottom; and when it has spread so far as to show itself at the holes h, h, h, these holes are shut by a stopper of clay. When the smoking at the top ceases, all the openings, as well as the top, are to be shut; and the oven left for cooling. Four or five days will, in most cases, be sufficient to burn an oven of turf charcoal. The holes h, h, h can be formed of old gunbarrels or iron pipes; bricks or earthenware pipes are very apt to break.

Turf charcoal is an excellent fuel, but expensive; it burns freely, and produces a fine heat. In Styria, sheet iron and reheating furnaces are heated by it: and in Bohemia, Bavaria, France, and Russia, it is extensively used in the blast furnaces, and produces, in most cases, very liquid, lively iron. Good turf coal is superior to charcoal in the blacksmith's fire.

VII. Charring of Brown Coal.

Brown coal is so imperfect a fuel in most cases, that it scarcely ever admits of being charred; but the best lignite of Europe is charred, though only with limited success. The subject is not sufficiently important to occupy our attention.

VIII. Charring of Bituminous Coal, Coke.

The manufacture of coke for blast furnace purposes is generally carried on in the open air, either in round heaps or rows; the latter mode is generally preferred. Coke burned in ovens will answer for that which is used in the furnace of locomotives, or for the purpose of generating steam; it is even useful in a foundry cupola oven; but in the blast furnace, or even in the refining fire, it ought not to be applied, for reasons we shall presently explain.

a. Coking in heaps is almost the same as charring wood in heaps; the main difference is that the heaps are smaller. For the purpose of coking in heaps, a level spot in the yard is selected, or a level staked out and prepared; a temporary chimney of common, or even of fire brick is erected, with alternate holes, some of which are especially necessary at the base. Around this chimney coarse coal is piled; the bottom, or level, is covered with coarse coal, in which

draft-channels must be left; coal may then be thrown on as it comes; but the coarse coal must be put in the centre of the heap. The height is of but little consequence, and may vary from three to six feet, according to convenience. But the chimney is to be built sufficiently high to reach over the top of the coal pile. Fig. 33 re

presents such a kiln or heap; a is the brick chimney. After the heap is ready, fire may be kindled around the base at different places, particularly near the horizontal channels; and the whole pile may then be slightly covered with coke dust. The fire will spread rapidly, and, in a few hours, will reach almost to the centre. A few air-holes may now be made in the cover with an iron bar, through which the heat and smoke may have vent. These airholes should be frequently renewed, because very bituminous coal is apt, by swelling, to close them. If the fire has been kindled in the morning, the heap will be in a good heat towards evening. It may then be covered heavily with dust, and the fire all around the heap choked. But the chimney is to be left open. The next day, or, at furthest, after the third day, the coke is ready for use. The object of leaving the chimney open is to retain a slow, but strong heat, as long as possible, in the heap, without wasting fuel. By this means, as much as possible of the sulphur contained in the coal will be expelled. If the ground where the heap is piled is somewhat moist, the hot steam arising from the ground will carry off a large portion of the sulphur in the form of sulphurous acid,