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ing from 3 to 10 tons, the operation, including the period of cooling, lasts from four to seven days. The coke obtained is of the highest quality, being dense and well burned. In some cases the cooling of the coke is effected by watering it before drawing. There is a certain amount of sulphur removed by this method, as the steam generated being brought into contact with the sulphide of iron in the heated mass, formed from pyrites in the coal, produces sulphuretted hydrogen and magnetic oxide of iron. The amount of desulphurization by this method is, however, practically insignifi cant, as the operation does not hist a sufficient time to allow the mass of the fuel to be affected. The proportion of sulphur in finished coke, as compared with that of the original coal, may be roughly stated at about one-half. It has been sought to reduce the amount by decomposing the residual ferrous sulphide in various ways, as by the addition of salt, carbonate of soda, lime, &c., to the coal before coking but none of these methods is found to be practically useful.

In the South Wales coal-field the ordinary form of coke oven is nearly rectangular, being about 14 feet long, 5 feet wide at the back, and 6 feet at the front or drawing ends ; the height to the crown of the cylindrical roof is 5 -feet 6 inches, with usually two charging holes. Two charges are worked weekly, the first, of 4^ tons, is finished in three days, while the second, of 5 tons, is allowed four days, so as to remain in the oven over Sunday. The yield in both cases is about the same.

Coppée's Coke Oven.

The addition of heating Hues exterior to the wall of the oven allows the time of coking to be very much shortened. Of the numerous contrivances proposed for this purpose, that of a Belgian engineer, Mr Coppee. has latterly come into favour in many places, as very well adapted for xise with comparatively dry coal. The coking chamber is a long narrow retort of fire brick, measuring about 30 feet in length, 17 inches in width at the front, and about 2 inches more at the back, where the charge is pushed out, with vertical walls about 3 feet high, covered by a low arched roof. One of these walls is solid, but the other contains twenty-eight vertical descending flues (/) which communicate with the interior at the springing of the roof, and below with the large flue of the same width as the oven, and running along its entire length. As usually built, a series or battery includes about thirty ovens, which are arranged in pairs as in the figure, from which it will be seen that the left hand oven (A) is heated by the joint current of gases on both sides, while B is heated on one side by its own gas, and on the other by that of the next oven to the right The current then passes along the bottom flue of A, and back through that of B, whence it escapes by a flue to the chimney, or may be led to a steam boiler if the waste heat is used, as is generally the case, for raising steam The working of the adjacent pair of ovens IS 80 arranged that they are drawn alternately at exactly inter mediate periods; thus supposing the time of coking to be forty- eight hours, A is drawn twenty-four hours after the charging of 1?, while the latter is in full activity, and keeps up the heat of the empty oven during charging, while necessarily the burning hydrocar bon gases given off during the first heating of the coal tend to keep up the heat in the adjoining oven. At Ebbw Vale, in Monmouthshire, where the coking requires only twenty-four hours, the ovens are numbered consecutively, theodd numbers being drawn and re-charged in the morning, and the even ones twelve hours later. The com bustion of the gases is effected by air which is brought in through special channels (c) in the brickwork communicating with the gas flues at the top, and becomes heated in the passage. The object sought to be obtained is the combustion of the gases as much as possible in the flues, and not in the oven itself. The oven is closed at both ends by cast-iron doors in two parts,, which can be opened together or separately during the drawing and recharging. The charging is effected through three holes (D D) in the roof, the coal, in the form of slack, being contained in hopper-shaped trams, running upon rails, which are run over the holes and emptied by drawing a slide. The charge is about 3 tons, and the yield from 36 to 44 cwt., according to the nature of the coal operated upon. The finished coke forms a prismatic mass, 30 feet long, 3 feet high, anil 16 inches broad ; it is pushed out by a ram, shaped like the cross section of the oven, which is moved by steam power acting upon a long racked rod. This apparatus, together with the engine and boiler for moving it, is mounted on a carriage moving on a railway in front of the range of ovens, so that it can be brought up to any one of them as required. The mass of coke is pushed out on to a floor running along the back, where it is immediately broken, and quenched by heavily watering the frag ments. The whole operation, including the drawing and recharg ing of the empty oven, is effected in about eight minutes. The yield of coke very closely approximates to that obtained by experi ments in crucibles. A similar kind of oven with outside heating flues, that of the Brothers Appolt, has been in use for several years on the Continent, more particularly in France. It differs from Coppee s in the position of the coking chambers, which are vertical instead of horizontal, the coal being charged from the top, and the finished coke dropped into a truck placed below. Various schemes have been proposed at different times for the purpose of utilizing the condensible products, such as tar, ammoniacal water, &c., given off during the earlier stages of the process of coking, but they are not generally found to be applicable to the manufacture of metallur. gical coke, being only suited for gas-works, where the quality of the coke is only a secondary consideration.

The slack of dry or non-caking coal, or anthracite, which cannot be coked alone, may* be converted into a useful coke by mixing it with a proportion of bituminous coal, or gas-pitch, or a mixture of both. At Swansea, a mixture of 60 to 70 per cent, of anthra cite with from 30 to 35 per cent, of bituminous coal, and 5 or 6 of gas pitch, made by grinding the ingredients in one of Carr s disin tegrator mills, is coked in the ordinary South Wales ovens, a thin layer of bituminous coal being placed above the charge before it is lighted, to prevent the pitch from burning to waste. The yield of coke : s about 80 per cent, of the weight of the charge. It is ex ceedingly hard, and about 23 per cent, heavier than that made from bituminous coal, with a correspondingly higher calorific value.

Coke is used for all purposes where a smokeless fire is required, as, for instance, in drying malt or hops, or in raising steam in locomotives within the limits of towns, also for producing strong local heat, as in melting metals (gold, silver, brass, or steel) in crucibles in air furnaces. In blast furnaces its value depends upon the difficulty of combustion, so that the particles keep their form until they reach the proper place of combustion at the point of entry of the blast in the lower part of the furnace. The great economy of fuel tliat has been effected in the process of iron smelting in the Cleveland district by increasing the height of the furnaces, is in great part due to the strength of the coke used, which is made in the south part of the Durham coal-field, and has sufficient cohesive power to bear the pressure of a column of iron-making materials from 80 to 100 feet in height without crushing, a result which cannot be obtained with the coke of other districts. Finely ground coke is used mixed with clay for making crucibles for steel melting, and also for filling the hearths of blast-furnaces in many German smelting works.

Apart from its convenience for special purposes, coke is not an economical fuel, the useful heating effect being about the same as that of an equal weight of coal. This circumstance lias led to the nearly general abandonment of coke and the substitution of raw coal as fuel in locomotive engines on railways.

For full accounts of the different systems of coke ovens and details of their construction, see Percy s Metallurgy, introductory volume on fuel, &c., 2d edition, London, 1875, and Jordan s Album du Cours de Metalhirgie, Paris, 1874.

(h. b.)

COKE, Sir Edward (1552-1633), one of the most

erudite of English lawyers, was born at Mileham, in Nor folk, on February 1, 1552. When only ten years old he lost his father, who was a bencher of Lincoln s Inn. From the grammar-school of Norwich he passed to Trinity College, Cambridge ; and after a course of three years, in 1572 ho entered the Inn to which his father had

belonged, To the study of law he devoted himself from