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aperture. In the Teleostomi abdominal pores are rare, but in most Teleostei the ova pass directly down oviducts, as they do in Arthropods, without entering the peritoneal cavity; there is little doubt, however, that these oviducts are originally coelomic in origin. In the Dipnoi abdominal pores are found, and probably serve as a passage for the sperm cells, since there are no vasa deferentia. In fishes a complete dorsal mesentery is seldom found in the adult; in many cases it only remains as a tube surrounding the vessels passing to the alimentary canal.

In the Amphibia, Reptilia and Aves, one cavity acts as pleura and peritoneum, though in the latter the lungs are not completely surrounded by a serous membrane. In many lizards the comparatively straight intestine, with its continuous dorsal mesentery and ventral mesentery in the anterior part of the abdomen, is very like a stage in the development of the human and other mammalian embryos. In the mammalia the diaphragm is complete and divides the pleuro-peritoneal cavity into its two constituent parts. In the lower mammals the derivatives of the original dorsal mesentery do not undergo as much fusion and obliteration as they do in adult man; the ascending and descending mesocolon is retained, and the transverse mesocolon contracts no adhesion to the great omentum. It is a common thing, however, to find a fenestrated arrangement of the great omentum which shows that its layers have been completely obliterated in many places.

In those animals, such as the rabbit, in which the tests are sometimes in the scrotum and sometimes in the abdomen, the communication between the peritoneum and the tunica vaginalis remains throughout life.

FOOTNOTE:

Some authorities hold that this alteration is not brought about by fusion, but by a dragging away of the posterior layer of the great omentum from the dorsal wall of the abdomen.

COEN, JAN PIETERSZOON , fourth governor-general of the Dutch East Indies, was born at Hoorn, and spent his youth at Rome in the house of the famous merchants the Piscatori. In 1607 he sailed from Amsterdam to the Indies as second commercial agent, and remained away four years. He had proved so capable that in 1612 he was sent out a second time at the head of a trading expedition. In the following year he was made a councillor and director-general of the East Indian trade. Afterwards he became president at Bantam, and on the 31st of October 1617 he was promoted in succession to Laurens Reaal to the post of governor-general. To his vigour and intrepidity the Dutch in no small measure owed the preservation and establishment of their empire in the East. He took and destroyed Jacatra, and founded on its ruins the capital of the Dutch East Indies, to which he gave the name of Batavia. In 1622 Coen obtained leave to resign his post and return to Holland, but in his absence great difficulties had arisen with the English at Amboina , and in 1627 under pressure from the directors of the East India Company he again returned as governor-general to Batavia. In 1629 he was able to beat off a formidable attack of the sultan of Mataram, sometimes styled emperor of Java, upon Batavia. He died the following year.

COENACULUM, the term applied to the eating-room of a Roman house in which the supper or latest meal was taken. It was sometimes placed in an upper storey and reached by an external staircase. The Last Supper in the New Testament was taken in the Coenaculum, the "large upper room" cited in St Mark and St Luke .

The term "coercion" is inevitably somewhat ambiguous, and depends on the circumstances of the case. In a political sense, the application of the Crimes Act of 1887 to Ireland was called "coercion" by those opposed to the English Unionist party and government, as being special legislation differing from the ordinary law applicable in the United Kingdom.

COEUR, JACQUES , founder of the trade between France and the Levant, was born at Bourges, in which city his father, Pierre Coeur, was a rich merchant. Jacques is first heard of about 1418, when he married Mac?e de L?odepart, daughter of Lambert de L?odepart, an influential citizen, provost of Bourges, and a former valet of John, duke of Berry. About 1429 he formed a commercial partnership with two brothers named Godard; and in 1432 he was at Damascus, buying and bartering, and transporting the wares of the Levant--gall-nuts, wools and silks, goats' hair, brocades and carpets--to the interior of France by way of Narbonne. In the same year he established himself at Montpellier, and there began those gigantic operations which have made him illustrious among financiers. Details are wanting; but it is certain that in a few years he placed his country in a position to contend not unsuccessfully with the great trading republics of Italy, and acquired such reputation as to be able, mere trader as he was, to render material assistance to the knights of Rhodes and to Venice herself.

At this moment the great trader's glory was at its height. He had represented France in three embassies, and had supplied the sinews of that war which had ousted the English from Normandy. He was invested with various offices of dignity, and possessed the most colossal fortune that had ever been amassed by a private Frenchman. The sea was covered with his ships; he had 300 factors in his employ, and houses of business in all the chief cities of France. He had built houses and chapels, and had founded colleges in Paris, at Montpellier and at Bourges. The house at Bourges was of exceptional magnificence, and remains to-day one of the finest monuments of the middle ages in France. He also built there the sacristy of the cathedral and a sepulchral chapel for his family. His brother Nicholas was made bishop of Lu?on, his sister married Jean Bochetel, the king's secretary, his daughter married the son of the viscount of Bourges, and his son Jean became archbishop of Bourges. But Coeur's gigantic monopoly caused his ruin. Dealing in everything, money and arms, peltry and jewels, brocades and woollens--a broker, a banker, a farmer--he had absorbed the trade of the country, and merchants complained they could make no gains on account of "that Jacquet." He had lent money to needy courtiers, to members of the royal family, and to the king himself, and his debtors, jealous of his wealth, were eager for a chance to cause his overthrow.

COEUR D'AL?NE , a tribe of North American Indians of Salishan stock. The name is said to have been originally that of a chief noted for his cruelty. The tribe has given its name to a lake, river and range of mountains in Idaho, where on a reservation the survivors, some 400, are settled.

The seeds are of a soft, semi-translucent, bluish or greenish colour, hard and tough in texture. The regions best adapted for the cultivation of coffee are well-watered mountain slopes at an elevation ranging from 1000 to 4000 ft. above sea-level, within the tropics, and possessing a mean annual temperature of about 65? to 70? F.

The Liberian coffee plant has larger leaves, flowers and fruits, and is of a more robust and hardy constitution, than Arabian coffee. The seeds yield a highly aromatic and well-flavoured coffee , and the plant is very prolific and yields heavy crops. Liberian coffee grows, moreover, at low altitudes, and flourishes in many situations unsuitable to the Arabian coffee. It grows wild in great abundance along the whole of the Guinea coast.

Up to the close of the 17th century the world's entire, although limited, supply of coffee was obtained from the province of Yemen in south Arabia, where the true celebrated Mocha or Mokka coffee is still produced. At this time, however, plants were successfully introduced from Arabia to Java, where the cultivation was immediately taken up. The government of Java distributed plants to various places, including the botanic garden of Amsterdam. The Portuguese introduced coffee into Ceylon. From Amsterdam the Dutch sent the plant to Surinam in 1718, and in the same year Jamaica received it through the governor Sir Nicholas Lawes. Within a few years coffee reached the other West Indian islands, and spread generally through the tropics of the New World, which now produce by far the greater portion of the world's supply.

Coffee thrives well also in the Philippines and Guam.

In 1906 there was an increased total of 2,680,855,878 lb, due to the Brazil export rising to 1,847,367,771 lb. The aggregate value of the coffee annually entering the world's markets is about ?40,000,000.

In many tropical countries much coffee is drunk, but as it is often produced locally exact figures are not available. The average consumption in the United Kingdom is about 50,000,000 lb per annum; about one-fifth only is produced in the British empire, and of this about nineteen-twentieths come from India and one-twentieth from the British West Indies.

Not only is ground coffee adulterated, but such mixtures as flour, chicory and coffee, or even bran and molasses, have been made up to simulate coffee beans and sold as such.

The leaves of the coffee tree contain caffeine in larger proportion than the seeds themselves, and their use as a substitute for tea has frequently been suggested. The leaves are actually so used in Sumatra, but being destitute of any attractive aroma such as is possessed by both tea and coffee, the infusion is not palatable. It is, moreover, not practicable to obtain both seeds and leaves from the same plant, and as the commercial demand is for the seed alone, no consideration either of profit or of any dietetic or economic advantage is likely to lead to the growth of coffee trees on account of their leaves.

COFFER , in architecture, a sunk panel in a ceiling or vault; also a casket or chest in which jewels or precious goods were kept, and, if of large dimensions, clothes. The marriage coffers in Italy were of exceptional richness in their carving and gilding and were sometimes painted by great artists.

COFFERDAM, in engineering. To enable foundations to be laid in a site which is under water, the engineer sometimes surrounds it with an embankment or dam, known as a cofferdam, to form an enclosure from which the water is excluded. Where the depth of water is small and the current slight, simple clay dams may be used, but in general cofferdams consist of two rows of piles, the space between which is packed with clay puddle. The dam must be sufficiently strong to withstand the exterior pressure to which it is exposed when the enclosed space is pumped dry.

COFFEYVILLE, a city of Montgomery county, Kansas, U.S.A., on the Verdigris river, about 150 m. S. of Topeka and near the southern boundary of the state. Pop. 2282; 4953, of whom 803 were negroes; 13,196; 12,687. Coffeyville is served by the Missouri Pacific, the Atchison, Topeka & Santa F?, the Missouri, Kansas & Texas, and the Saint Louis, Iron Mountain & Southern railways, and by inter-urban electric railway to Independence. It is in the Kansas natural-gas field, ships large quantities of grain, and has a large zinc oxide smelter and a large oil refinery, and various manufactures, including vitrified brick and tile, flour, lumber, chemicals, window glass, bottles, pottery and straw boards. The municipality owns and operates its water-works and electric lighting plant. Coffeyville, named in honour of A. M. Coffey, who was a member of the first legislature of the territory of Kansas, was founded in 1869, but in 1871 it was removed about 1 m. from its original site, now known as "old town." It was incorporated as a city of the third class in 1872 and received a new charter in 1887. Coffeyville became a station on the Leavenworth, Lawrence & Galveston railway , and for several years large numbers of cattle were driven here from Indian Territory and Texas for shipment; in fact, the city's chief importance was as a trade centre for the north part of Indian Territory until natural gas was found here in large quantities in 1892.

COFFIN , the receptacle in which a corpse is confined. The Greeks and Romans disposed of their dead both by burial and by cremation. Greek coffins varied in shape, being in the form of an urn, or like the modern coffins, or triangular, the body being in a sitting posture. The material used was generally burnt clay, and in some cases this had obviously been first moulded round the body, and so baked. Cremation was the commonest method of disposing of the dead among the Romans, until the Christian era, when stone coffins came into use. Examples of these have been frequently dug up in England. In 1853, during excavations for the foundations of some warehouses in Hayden Square, Minories, London, a Roman stone coffin was found within which was a leaden shell. Others have been found at Whitechapel, Stratford-le-Bow, Old Kent Road and Battersea Fields, and in great numbers at Colchester, York, Southfleet and Kingsholme near Gloucester. In early England stone coffins were only used by the nobles and the wealthy. Those of the Romans who were rich enough had their coffins made of a limestone brought from Assos in Troas, which it was commonly believed "ate the body"; hence arose the name sarcophagus .

The most primitive wooden coffin was formed of a tree-trunk split down the centre, and hollowed out. The earliest specimen of this type is in the Copenhagen museum, the implements found in it proving that it belonged to the Bronze Age. This type of coffin, more or less modified by planing, was used in medieval Britain by those of the better classes who could not afford stone, but the poor were buried without coffins, wrapped simply in cloth or even covered only with hay and flowers. Towards the end of the 17th century, coffins became usual for all classes. It is worth noting that in the Burial Service in the Book of Common Prayer the word "coffin" is not used.

Among the American Indians some tribes, e.g. the Sacs, Foxes and Sioux, used rough hewn wooden coffins; others, such as the Seris, sometimes enclosed the corpse between the carapace and plastron of a turtle. The Seminoles of Florida used no coffins, while at Santa Barbara, California, canoes containing corpses have been found buried though they may have been intended for the dead warrior's use in the next world. Rough stone cists, too, have been found, especially in Illinois and Kentucky. In their tree and scaffold burial the Indians sometimes used wooden coffins, but oftener the bodies were simply wrapped in blankets. Canoes mounted on a scaffold near a river were used as coffins by some tribes, while others placed the corpse in a canoe or wicker basket and floated them out into the stream or lake . The aborigines of Australia generally used coffins of bark, but some tribes employed baskets of wicker-work.

See also FUNERAL RITES; CREMATION; Burial and Burial Acts; EMBALMING; MUMMY, &c.

COG. , a broadly built, round-shaped ship, used as a trader and also as a ship of war till the 15th century. , a tooth in a series of teeth, morticed on to, or cut out of the circumference of a wheel, which works with the tooth in a corresponding series on another wheel . , a slang term for a form of cheating at dice. The early uses of the word show that this was done not by "loading" the dice, as the modern use of the expression of "cogged dice" seems to imply, but by sleight of hand in directing the fall or in changing the dice.

COGNITION , in psychology, a term used in its most general sense for all modes of being conscious or aware of an object, whether material or intellectual. It is an ultimate mode of consciousness, strictly the presentation of an object to consciousness; in its complete form, however, it seems to involve a judgment, i.e. the separation from other objects of the object presented. The psychological theory of cognition takes for granted the dualism of the mind that knows and the object known; it takes no account of the metaphysical problem as to the possibility of a relation between the ego and the non-ego, but assumes that such a relation does exist. Cognition is therefore distinct from emotion and conation; it has no psychological connexion with feelings of pleasure and pain, nor does it tend as such to issue in action.

COGNIZANCE , knowledge, notice, especially judicial notice, the right of trying or considering a case judicially, the exercise of jurisdiction by a court of law. In heraldry a "cognizance" is an emblem, badge or device, used as a distinguishing mark by the body of retainers of a royal or noble house.

COHEN , a Jewish family name, implying descent from the ancient Hebrew priests. Many families claiming such descent are, however, not named Cohen. Other forms of the name are Cohn, Cowen, Kahn.

COHOES, a city of Albany county, New York, U.S.A., about 9 m. N. of Albany, at the confluence of the Mohawk and Hudson rivers. Pop. 22,509; 23,910, of whom 7303 were foreign-born; 24,709. It is served by the New York Central & Hudson River and the Delaware & Hudson railways, by electric lines to Troy and Albany, and by the Erie and Champlain canals. It is primarily a manufacturing city. Hosiery and knit goods, cotton cloth, cotton batting, shoddy, underwear and shirts and collars are the principal products, but there are also extensive valve works and manufactories of pulp, paper and paper boxes, beer, pins and needles, tools and machinery, and sash, doors and blinds. The value of the factory products in 1905 was ,289,822, of which ,126,873, or 40.1%, was the value of hosiery and knit goods, Cohoes ranking fifth among the cities of the United States in this industry, and showing a higher degree of specialization in it than any other city in the United States except Little Falls, N.Y. The Falls of the Mohawk, which furnish power for the majority of the manufacturing establishments, are 75 ft. high and 900 ft. broad, a large dam above the falls storing the water, which is conveyed through canals to the mills. Below the falls the river is crossed by two fine iron bridges. The city has a public library, a normal training school and the St Bernard's Academy. Cohoes was a part of the extensive manorial grant made to Killian Van Rensselaer in 1629 and it was probably settled very soon afterwards. It was incorporated as a village in 1848 and was chartered as a city in 1870.

In biology, "cohort" is a term for a group of allied orders or families of plants or animals.

COIMBATORE, a city and district of British India, in the Madras presidency. The city is situated on the left bank of the Noyil river, 305 m. from Madras by the Madras railway. In 1901 it had a population of 53,080, showing an increase of 14% in the decade. The city stands 1437 ft. above sea-level, is well laid out and healthy, and is rendered additionally attractive to European residents by its picturesque position on the slopes of the Nilgiri hills. It is an important industrial centre, carrying on cotton weaving and spinning, tanning, distilling, and the manufacture of coffee, sugar, manure and saltpetre. It has two second-grade colleges, a college of agriculture, and a school of forestry.

The DISTRICT OF COIMBATORE has an area of 7860 sq. m. It may be described as a flat, open country, hemmed in by mountains on the north, west and south, but opening eastwards on to the great plain of the Carnatic; the average height of the plain above sea-level is about 900 ft. The principal mountains are the Anamalai Hills, in the south of the district, rising at places to a height of between 8000 and 9000 ft. In the west the Palghat and Vallagiri Hills form a connecting link between the Anamalai range and the Nilgiris, with the exception of a remarkable gap known as the Palghat Pass. This gap, which completely intersects the Ghats, is about 20 m. wide. In the north is a range of primitive trap-hills known as the Cauvery chain, extending eastwards from the Nilgiris, and rising in places to a height of 4000 ft. The principal rivers are the Cauvery, Bhavani, Noyil, and Amravati. Numerous canals are cut from the rivers for the purpose of affording artificial irrigation, which has proved of immense benefit to the country. Well and tank water is also largely used for irrigation purposes. Coimbatore district was acquired by the British in 1799 at the close of the war which ended with the death of Tippoo. In 1901 the population was 2,201,782, showing an increase of 10% in the preceding decade. The principal crops are millet, rice, other food grains, pulse, oilseeds, cotton and tobacco, with a little coffee. Forests cover nearly 1 1/2 million acres, yielding valuable timber , and affording grazing-ground for cattle. There are several factories for pressing cotton, and for cleaning coffee, oil-cake presses, tanneries and saltpetre refineries. Cereals, cotton, forest products, cattle and hides, and brass and copper vessels are the chief exports from the district. The south-west line of the Madras railway runs through the district, and the South Indian railway joins this at Erode.

COIMBRA, the capital of an administrative district formerly included in the province of Beira, Portugal; on the north bank of the river Mondego, 115 m. N.N.E. of Lisbon, on the Lisbon-Oporto railway. Pop. 18,144. Coimbra is built for the most part on rising ground, and presents from the other side of the river a picturesque and imposing appearance; though in reality its houses have individually but little pretension, and its streets are, almost without exception, narrow and mean. It derives its present importance from being the seat of the only university in the kingdom--an institution which was originally established at Lisbon in 1291, was transferred to Coimbra in 1306, was again removed to Lisbon, and was finally fixed at Coimbra in 1527. There are five faculties--theology, law, medicine, mathematics and philosophy--with more than 1300 students. The library contains about 150,000 volumes, and the museums and laboratories are on an extensive scale. In connexion with the medical faculty there are regular hospitals; the mathematical faculty maintains an observatory from which an excellent view can be obtained of the whole valley of the Mondego; and outside the town there is a botanic garden , which also serves as a public promenade. Among the other educational establishments are a military college, a royal college of arts, a scientific and literary institute, and an episcopal seminary.

The administrative district of Coimbra coincides with the south-western part of Beira; pop. 332,168; area 1508 sq. m.

CO?N, a town of southern Spain in the province of M?laga; 18 m. W.S.W. of the city of M?laga. Pop. 12,326. Co?n is finely situated on the northern slope of the Sierra de Mijas, overlooking the small river S?co and surrounded by vineyards and plantations of oranges and lemons. There are marble quarries in the neighbourhood, and, despite the lack of a railway, Co?n has a thriving agricultural trade. The population increased by more than half between 1880 and 1900.

COIN , properly the term for a wedge-shaped die used for stamping money, and so transferred to the money so stamped; hence a piece of money. The form "quoin" is used for the external angle of a building , and "coign," also a projecting angle, survives in the Shakespearean phrase "a coign of vantage."

COINAGE OFFENCES. The coinage of money is in all states a prerogative of the sovereign power; consequently any infringement of that prerogative is always severely punished, as being an offence likely to interfere with the well-being of the state.

In the United Kingdom the statute law against offences relating to the coin was codified by an act of 1861. The statute provides that whoever falsely makes or counterfeits any coin resembling or apparently intended to resemble or pass for any current gold or silver coin of the realm , or gilds, silvers, washes, cases over or colours with materials capable of producing the appearance of gold or silver a coin or a piece of any metal or mixture of metals, or files or alters it, with intent to make it resemble or pass for any current gold or silver coin , or who buys, sells, receives or pays a false gold or silver coin at a lower rate than its denomination imports, or who receives into the United Kingdom any false coin knowing it to be counterfeit , or who, without lawful authority or excuse, knowingly makes or mends, buys or sells, or has in his custody or possession, or conveys out of the Royal Mint any coining moulds, machines or tools, is guilty of felony . The punishment for such offences is either penal servitude for life or for not less than three years, or imprisonment for not more than two years, with or without hard labour. Whoever impairs, diminishes or lightens current gold or silver coin, with intent to pass same, is liable to penal servitude for from three to fourteen years , and whoever has in his possession filings or clippings obtained by impairing or lightening current coin is liable to the same punishment, or to penal servitude for from three to seven years. The statute also makes provision against tendering or uttering false gold or silver coin, which is a misdemeanour, punishable by imprisonment with or without hard labour. Provision is also made with respect to falsely making, counterfeiting, tendering or uttering copper coin, exporting false coin, or defacing current coin by stamping names or words on it, and counterfeiting, tendering or uttering coin resembling or meant to pass as that of some foreign state. The act of 1861 applies to offences with respect to colonial coins as well as to those of the United Kingdom.

COIR , a rough, strong, fibrous substance obtained from the outer husk of the coco-nut.

COIRE , the capital of the Swiss canton of the Grisons. It is built, at a height of 1949 ft. above the sea-level, on the right bank of the Plessur torrent, just as it issues from the Schanfigg valley, and about a mile above its junction with the Rhine. It is overshadowed by the Mittenberg and Pizokel , hills that guard the entrance to the deep-cut Schanfigg valley. In 1900 it contained 11,532 inhabitants, of whom 9288 were German-speaking, 1466 Romonsch-speaking, and 677 Italian-speaking; while 7561 were Protestants, 3962 Romanists and one a Jew. The modern part of the city is to the west, but the old portion, with all the historical buildings, is to the east. Here is the cathedral church of St Lucius . Built between 1178 and 1282, on the site of an older church, it contains many curious medieval antiquities , as well as a picture by Angelica Kaufmann, and the tomb of the great Grisons political leader Jenatsch . Opposite is the Bishop's Palace, and not far off is the Episcopal Seminary . Not far from these ancient monuments is the new Raetian Museum, which contains a great collection of objects relating to Raetia , who explored the high snowy regions around the sources of the Rhine). One of the hospitals was founded by the famous Capuchin philanthropist, Father Theodosius Florentini , who was long the Romanist cur? of Coire, and whose remains were in 1906 transferred from the cathedral here to Ingenbohl , his chief foundation. Coire is 74 m. by rail from Z?rich, and is the meeting-point of the routes from Italy over many Alpine passes as well as from the Engadine , so that it is the centre of an active trade , though it possesses also a few local factories.

COKE, SIR EDWARD , English lawyer, was born at Mileham, in Norfolk, on the 1st of February 1552. From the grammar school of Norwich he passed to Trinity College, Cambridge; and in 1572 he entered Lincoln's Inn. In 1578 he was called to the bar, and in the next year he was chosen reader at Lyon's Inn. His extensive and exact legal erudition, and the skill with which he argued the intricate libel case of Lord Cromwell , and the celebrated real property case of Shelley , soon brought him a practice never before equalled, and caused him to be universally recognized as the greatest lawyer of his day. In 1586 he was made recorder of Norwich, and in 1592 recorder of London, solicitor-general, and reader in the Inner Temple. In 1593 he was returned as member of parliament for his native county, and also chosen speaker of the House of Commons. In 1594 he was promoted to the office of attorney-general, despite the claims of Bacon, who was warmly supported by the earl of Essex. As crown lawyer his treatment of the accused was marked by more than the harshness and violence common in his time; and the fame of the victim has caused his behaviour in the trial of Raleigh to be lastingly remembered against him. While the prisoner defended himself with the calmest dignity and self-possession, Coke burst into the bitterest invective, brutally addressing the great courtier as if he had been a servant, in the phrase, long remembered for its insolence and its utter injustice--"Thou hast an English face, but a Spanish heart!"

In 1582 Coke married the daughter of John Paston, a gentleman of Suffolk, receiving with her a fortune of ?30,000; but in six months he was left a widower. Shortly after he sought the hand of Lady Elizabeth Hatton, daughter of Thomas, second Lord Burghley, and granddaughter of the great Cecil. Bacon was again his rival, and again unsuccessfully; the wealthy young widow became--not, it is said, to his future comfort--Coke's second wife.

Coke did not suffer these losses with patience. He offered his daughter Frances, then little more than a child, in marriage to Sir John Villiers, brother of the favourite Buckingham. Her mother, supported at first by her husband's great rival and her own former suitor, Bacon, objected to the match, and placed her in concealment. But Coke discovered her hiding-place; and she was forced to wed the man whom she declared that of all others she abhorred. The result was the desertion of the husband and the fall of the wife. It is said, however, that after his daughter's public penance in the Savoy church, Coke had heart enough to receive her back to the home which he had forced her to leave. Almost all that he gained by his heartless diplomacy was a seat in the council and in the star-chamber.

COKE , the product obtained by strongly heating coal out of contact with the air until the volatile constituents are driven off; it consists essentially of carbon, the so-called "fixed carbon," together with the incombustible matters or ash contained in the coal from which it is derived. In addition to these it almost invariably contains small quantities of hydrogen, oxygen and nitrogen, the whole, however, not exceeding 2 or 3%. It also contains water, the amount of which may vary considerably according to the method of manufacture. When produced rapidly and at a low heat, as in gas-making, it is of a dull black colour, and a loose spongy or pumice-like texture, and ignites with comparative ease, though less readily than bituminous coal, so that it may be burnt in open fire-places; but when a long-continued heat is used, as in the preparation of coke for iron and steel melting, the product is hard and dense, is often prismatic in structure, has a brilliant semi-metallic lustre and silvery-grey colour, is a conductor of heat and electricity, and can only be burnt in furnaces provided with a strong chimney draught or an artificial blast. The strength and cohesive properties are also intimately related to the nature and composition of the coals employed, which are said to be caking or non-caking according to the compact or fragmentary character of the coke produced.

Formerly coke was made from large coal piled in heaps with central chimneys like those of the charcoal burner, or in open rectangular clamps or kilns with air flues in the enclosing walls; but these methods are now practically obsolete, closed chambers or ovens being generally used. These vary considerably in construction, but may be classified into three principal types:-- direct heated ovens, flue-heated ovens, condensing ovens. In the first class the heating is done by direct contact or by burning the gases given off in coking within the oven, while in the other two the heating is indirect, the gas being burned in cellular passages or flues provided in the walls dividing the coking chambers, and the heat transmitted through the sides of the latter which are comparatively thin. The arrangement is somewhat similar to that of a gas-works retort, whence the name of "retort ovens" is sometimes applied to them. The difference between the second and third classes is founded on the treatment of the gases. In the former the gas is fired in the side flues immediately upon issuing from the oven, while in the latter the gases are first subjected to a systematic treatment in condensers, similar to those used in gas-works, to remove tar, ammonia and condensable hydrocarbons, the incondensable gases being returned to the oven and burned in the heating flues. These are generally known as "by-product ovens."

Beehive oven.

The simplest form of coke oven, and probably that still most largely used, is the so-called "beehive oven." This is circular in plan, from 7 to 12 ft. in diameter, with a cylindrical wall about 2 1/2 ft. high and a nearly hemispherical roof with a circular hole at the top. The floor, made of refractory bricks or slabs, is laid with a slight slope towards an arched opening in the ring wall, which is stopped with brickwork during the coking but opened for drawing the finished charge. The ovens are usually arranged in rows or banks of 20 to 30 or more, with their doors outwards, two rows being often placed with a longitudinal flue between them connected by uptakes with the individual ovens on either side. A railway along the top of the bank brings the coal from the screens or washery. The largest ovens take a charge of about 5 tons, which is introduced through the hole in the roof, the brickwork of the empty oven being still red hot from the preceding charge, and when levelled fills the cylindrical part nearly to the springing of the roof. The gas fires as it is given off and fills the dome with flame, and the burning is regulated by air admitted through holes in the upper part of the door stopping. The temperature being very high, a proportion of the volatile hydrocarbons is decomposed, and a film of graphitic carbon is deposited on the coke, giving it a semi-metallic lustre and silvery grey colour. When the gas is burned off, the upper part of the door is opened and the glowing charge cooled by jets of water thrown directly upon it from a hose, and it is subsequently drawn out through the open door. The charge breaks up into prisms or columns whose length corresponds to the depth of the charge, and as a rule is uniform in character and free from dull black patches or "black ends." The time of burning is either 48 or 72 hours, the turns being so arranged as to avoid the necessity of drawing the ovens on Sunday. The longer the heat is continued the denser the product becomes, but the yield also diminishes, as a portion of the finished coke necessarily burns to waste when the gas is exhausted. For this reason the yield on the coal charged is usually less than that obtained in retort ovens, although the quality may be better. Coals containing at most about 35% of volatile matter are best suited for the beehive oven. With less than 25% the gas is not sufficient to effect the coking completely, and when there is a higher percentage the coke is brittle and spongy and unsuited for blast furnace or foundry use. The spent flame from the ovens passes to a range of steam boilers before escaping by the chimney.

Retort oven.

In some cases, instead of the small coal being charged through the roof of the oven and levelled by hand, it is formed into blocks by being stamped in a slightly moistened condition in a mould consisting of a bottom plate or peel on a racked rod like that of the ram, with movable sides and ends. This, when the ends are removed, is pushed forward into the oven, and the bottom plate is withdrawn by reversing the rack motion. The moulding box is mounted on a carriage like that of the ram, the two being sometimes carried on the same framing. The moulding is done at a fixed station in the centre of the range of ovens by a series of cast-iron stampers driven by an electric motor. This system is useful for coals low in volatile matter, which do not give a coherent coke under ordinary conditions.

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