fourths of the whole; and being slowly burnt, affords thirteen per cent. of ashes, which consists mostly of argillaceous earth; and about 300th parts of them are magnetic. It is found in England and among some alluminous ores in Sweden.'

COAL, KILKENNY, is the lightest of any; its specific gravity being only about 1400. It contains the largest quantity of asphaltum; burns with less smoke and flame, and more intensely, though more slowly, than the cannel coal. The quantity of earth it contains does not exceed one-twentieth part of its weight; but this kind of coal is frequently mixed with pyites. It is found in Kilkenny, Ireland. Its quality of burning without smoke, is proverbially used as an encomium on the country.

COAL, PIT. Pit coal is a black, solid, compact, brittle mass, of moderate hardness, lamellated structure, more or less shining, but seldom capable of a good polish; and does not melt when heated. According to Kirwan, it consists of petrol or asphaltum, intimately mixed with a small portion of earth chiefly argillaceous; seldom calcareous; and frequently mixed with pyrites. A red tincture is extracted from it by a spirit of wine, but caustic alkali attacks the bituminous part. The varieties of this coal,' says Mr. Magellan, are very numerous, according to the different substances with which it is mixed.' See COAL-MINE, Sect. VIII. But in regard to their economical uses, only two kinds are taken notice of by the British legislature, viz. culm, and caking coals. The caking coals, in burning, show an incipient fusion, so that their smallest pieces unite in the fire into one mass; by which means the smallest pieces, and even the mere dust of this kind, are almost equally valuable with the largest pieces. The culm does not fuse or unite in the fiercest fire; so that the small coal, being unfit for domestic purposes, can only be used in burning limestone. See CULM, and LITHANTHRAX.

COAL, SLATE, contains such a quantity of argillaceous earth, that it looks like common slate; however it burns by itself with a flame. M. Magellan is of opinion that this is the bituminous schistus, already described under CLAY. This schistus is of a dark, bluish, rusty color; when thrown on the fire it burns with a lively flame, and almost as readily as the oily wood of dry olive tree, or lignum vitæ ; emitting the very disagreeable smell of petrol. Such large quarries of it are found near Purbeck in Dorsetshire, that the poorer part of the inhabitants are thence supplied with fuel. From the appearance of this slaty coal, Cronstadt had been induced to suppose that the earth of all kinds of coal is argillaceous, though it is not so easy to distinguish it after being burnt. The pit coals, he says, contain more or less of the vitriolic acid; for which reason the smoke arising from them attacks silver in the same manner as sulphur does, let the coals be ever so free from marcasite, which however, is often imbedded or mixed with them. COAL, SULPHUREOUS, consists of the former kinds mixed with a very considerable portion of pyrites; whence it is apt to moulder and break when exposed to the air, after which water will

act upon it. It contains yellow spots that look like metal; burns with a sulphureous smell, leaving behind it either slag or sulphureous ashes, or both. Its specific gravity is 1500 or

more.

The above are the most considerable varieties of coal commonly known; but we must not imagine that each of them is to be met with in a homogeneous state. On the contrary, the different qualities and proportions of their ingredients make a vast number of other varieties, fit for different purposes, according to the quality and quantity of those they contain. Some of the finer sorts generally run like veins between those of a coarser kind. M. Magellan observed in the fine coal employed in a curious button manufactory at Birmingham, that it produced a much clearer flame than he had ever observed from common coal; yet, on enquiry, he found that the former was picked out from the common coal of the country, through which it ran in veins, and was easily distinguished by the manufacturers. Fourcroy remarks, that this fossil bitumen, when heated in contact with a body in combustion, provided it has a free access of air, kindles the more slowly and with the greater difficulty, in proportion as it is more weighty and compact. When once kindled, it emits a strong and durable heat, and burns for a long time before it is consumed. The matter that is burned, and produces the flame appears very dense, and seems united to some other substance which retards its destruction. On burning it emits a peculiar and strong smell, which is not at all sulphureous when the coal contains no pyrites. When the combustible, oily, and other volatile parts of the coal are dissipated, if the combustion be ther stopped, the remainder is reduced to a true charred state, and is called coak. It is well known, says M. Magellan, that the English method of burning pit coal into coak has been a most profitable and happy acquisition for the smelting our ores, and for many other metallurgical and chemical processes in this island. But the ingenious and extensive undertaking of lord Dundonald, by which he turns to very valuable purposes the mines of coal in his and other estates, building ovens of a proper construction for burning pit-coal into coak, and at the same time for collecting, in separate receptacles, the volatile alkali, oil, tar, and pitch, which were generally lost by the usual method, deserves to be noticed, as it affords a very remarkable instance of the great losses to mankind, for want of carefully attending to every result from great processes of art when made on a large scale. These ovens are so contrived, as to admit an under supply of air; and the coals, after being kindled, decompose themselves by a slow but incomplete combustion, which does not destroy the ingredients. The residuum left in the oven proves to be most excellent cinders or coaks, whilst the volatile parts which otherwise would be dissipated in the air, are separated and condensed in reservoirs or receptacles of capacious size, placed at proper distances beyond the reach of fire. M. Faujas de St. Fond, who visited these works in a trip he made to Scotland, undertook to erect a similar kind of oven in France. On subjecting

pit coal of any kind to distillation in close vessels, it first yields a phlegm or watery liquor; then an ethereal or volatile oil; afterwards a volatile alkali; and lastly, a thick and greasy oil; but it is remarkable, that, by rectifying this last oil, a transparent thin and light oil of a straw color is produced, which, being exposed to the air, becomes black like animal oils. From these and similar observations, Messrs. Magellan, Chattal, and others, have inferred, that pit coal is originally a vegetable substance.

COAL, SMALL, is a term sometimes used for a sort of charcoal prepared from the spray and brushwood stripped off from the branches of coppice wood, sometimes bound in barns for that purpose, and sometimes charred without binding, in which case it is called coming together.

Kirwan divides carbonaceous substances into four species, of which the first two contain almost all the varieties of coal. i. Native mineral carbon, the blende kohle of Werner, of which the coal found near Kilkenny and the culm of Wales is a species. The former he thus characterises :Its color is black, and when fresh broken some parts of it generally display a violet color. Its lustre, 4. Metallic. Transparency, 0. Fracture foliated, and the course of the lamella variously and confusedly directed. Its fragments, from 2 to 3, often coated with whitish illinitions. Hardness, 7. Specific gravity, 1.526. Will not burn till wholly ignited, and then slowly consumes, without caking, or emitting flame or

smoke.

ii. Mineral carbon, impregnated with bitumen, which he subdivides into three families, and thus describes ::

First Family.-Mineral carbon, impregnated with maltha; cannel coal.-First variety.-Compact. This is found chiefly in Lancashire, its proper name is candle-coal, as it burns like a candle; but candles in that shire are called cannels. Its color is black. Lustre, common. Transparency, 0. Cross fracture, conchoidal. Fragments, from 2 to 3. Hardness, from 7 to 8. Specific gravity, 1.273 per Watson, or 1-232 by my trials. Does not stain the fingers; easily kindles, and burns with a large bright flame, but of short duration, and then leaves a sooty residuum that difficultly burns; does not cake; 240 grains of it heated until all the coaly part was consumed, left 7.5 of reddish-brown ashes, mostly argillaceous and siliceous; 100 parts of it contain by my analysis 75 carbon, 217 maltha, and 312 of ashes.

Second Variety.-Slaty.-This coal comes to us from Scotland, where it is called splentcoal. Its color is grayish-black. Lustre, 2, common. Transparency, 0. Fracture, partly slaty and partly imperfectly conchoidal. Fragments, 3. Hardness, from 5 to 8. Brittle. Specific gravity, 1-426, by my trials; burns as the former variety, but soon ceases to flame; does not cake, and leaves a stony residuum; 240 grains of it, treated as the former, left 50 grains of reddish-gray ashes; 100 parts of it contain by my analysis 47 6 carbon, 316 maltha, and 20,8 of ashes.I even doubt,' says this mineralogist whether it contains so much carbon,

for the best specimens discovered by the smell, when inflamed, a proportion of sulphur.'

Second Family.-Mineral carbon, impregnated with asphalt and maltha, in various proportions. Peckhole, Schiefer, kohle of Werner.-Its color is more or less perfectly black, sometimes presenting bright reddish-yellow illinitions, sometimes variegated. Lustre, from 2 to 4, seldom common, mostly greasy or metallic. Transparency 0. Fracture various, mostly foliated, plain, or curved, large or small granularly foliated, sometimes in layers of contrary directions, sometimes promiscuously directed, sometimes presenting small conchoidal distinct concretions, sometimes striated; often in the gross; slaty. Its fragments, 2, often oblong parallelopipeds. Hardness, from 4 to 6. Specific gravity, from 1.25 to 137, stains the fingers, if moist, or disintegrating, otherwise not. Inflames more slowly, but burns longer than the former family, and cakes more or less, according to the proportion of asphalt. It is often contaminated with lumps, or veins of martial pyrites, sometimes with alum, or intersected with veins of spar. Of this family there are numerous varieties.

First Variety. — From Whitehaven. — Black. Lustre 3, greasy. Fracture plane foliated. Fragments 2. Hardness 6, very brittle. Specific gravity 1.257; 240 grains of it exposed to a heat of 27° for five hours, after flaming a considerable time, caked, and at last left fourteen grains of reddish ashes; 100 parts of it contain by my analysis 56-8 carbon, and 43 of a mixture of asphalt and maltha, in which the asphalt predominates.

Second Variety. From Wigan. — Black. Lustre 3, greasy, often with bright yellowish illinitions. Fracture foliated, some laminæ uniformly, some promiscuonsly directed, in the gross slaty. Fragments 2. Hardness 6. Specific gravity 1.268, burns more quickly than the former; 382 grains of it exposed in an open crucible, like the former, to a heat of 27°, for four hours, left a residuum of 5-13 grains of reddish-brown ashes.

Third Variety. From Swansea. — Black. Lustre, 2. Fracture, foliated, but from a contrary direction of the lamellæ seems in part fibrous. Fragments 2. Hardness 5, very brittle. Specific gravity 1.357, burns more slowly than the former varieties; 240 grains of it, treated as above, left eight grains of yellowishred ashes. One hundred parts of it contain 73-53 of carbon, 23-16 of a mixture of asphalt and maltha, in which the former appears to predominate, and 5,21 of gray ashes.

Fourth Variety. From Leitrim.-Black. Lustre 3. Fracture, foliated. Fragments, 2. Hardness, 6, very brittle. Specific gravity, 1,351; 240 grains of it exposed to heat, as before, left in three hours a residuum of 12,5 of reddishgray ashes; one hundred parts of it contain 71,42 of carbon, 23,37 of a mixture of asphalt and maltha, in which the latter appears to predominate, and 521 of gray ashes.

Fifth Variety.-From Irvine, in Scotland.Black. Presents layers in contrary directions, hence often called ribband-coal. Lustre of the alternate layers 3, 2. Fracture small grained

and coarse grained curved foliated. Hardness from 4 to 5. Specific gravity 1.259. Its composition I have not examined. The specific gravity of good bituminous coal never exceeds 1-4, except it contains some quantity of interspersed pyrites.

Third Family-Carbon bituminated, impregnated with a notable proportion of stony matter. Spurious Coal.-I call the proportion of stony matter notable when it exceeds 25 per cent. Its color is grayish-black. Lustre 01. Fracture slaty or earthy. Fragments quadrangular, 3. Hardness from 7 to 8. Specific gravity from 1.500 to 1.600. It commonly explodes and bursts when heated; generally found amidst strata of genuine coal. Buffon tells us that the coal of Alaies is mixed with such a quantity of limestone, that it is often burned for the sole purpose of obtaining lime from it.-2 Buffon Mineralog. 8vo. p. 189.

Macquer remarked long ago that nitre detonates with no oily or inflammable matter, until such matter is reduced to coal, and then only in proportion to the carbonaceous matter it contains. Hence it occurred to Mr. Kirwan that, as coals appear in distillation to be for the most part merely compounds of carbon and bitumen, it should follow that, by the decomposition of nitre, the quantity of carbon in a given quantity of every species of coal may be discovered, and the proportion of bitumen inferred. This celebrated chemist accordingly projected on a certain portion of nitre in a state of fusion, successive fragments of various kinds of coal, till the deflagration ceased. Coal, when in fine powder, was thrown out of the crucible. The experiments seem to have been judiciously performed, and the results are therefore entitled to as much confidence as the method permits. Lavoisier and Kirwan state, that about thirteen parts of dry wood charcoal decompose 100 of nitre.

100 parts of the best English coal give, of coak, 63 by Mr. Jars. 100 do. 73. Hielm. 100 do. Newcastle do. 58. Dr. Watson. Kirwan says he copied the result, for Newcastle coal, from Dr. Watson.

Werner, without including the beds of coal found on a sandstone or limestone basis, has ascertained three distinct coal formations.

The first, or oldest formation, he calls the independent coal formation, because the individual depositions of which it is composed, are inde

pendent of each other, and are not connected. The second is that which occurs in the newest floetz-trap formation; and the third occurs in alluvial land. Werner observes, that a fourth formation might be added, which would comprehend peat and other similar substances; so that we should have a beautiful and uninterrupted series, from the oldest formation to the peat, which is daily forming under the eye. The independent formation contains exclusively coarse coal, foliated coal, cannel coal, slate coal, a kind of pitch The latter was first coal, and slaty glance coal. found in this formation in Arran, Dumfries-shire, Ayrshire and at Westcraigs, by Proffessor Jameson. The formation in the newest floetz-trap contains distinct pitch coal, columnar coal, and conchoidal glance coal. The alluvial formation contains almost exclusively earth coal and bituminous wood. The first formation, besides coal, contains three rocks which are peculiar to it; these are a conglomerate, which is more or less coarse-grained; a friable sandstone, which is always micaceous; and lastly, slate-clay. But besides these, there occur also beds of harder sandstone, marl, limestone, porphyritic stone, bituminous shale, clayironstone; and, as discovered by Proffessor Jameson, greenstone, amygdaloid, and graphite. The slate-clay is well characterised, by the great variety of vegetable impressions of such plants as The smaller flourish in marshes and woods. plants and reeds occur in casts or impressions always laid in the direction of the strata; but the larger arborescent plants often stand erect, and their stems are filled with the substance of the superincumbent strata, which seems to show that these stems are in their original position. The leaves and stems resemble those of palms and ferns. The central, northern, and western coalmines of England; the river coal districts of the Forth and the Clyde, and the Ayrshire, and in part the Dumfries-shire coals, belong to this formation, as well as the coals in the northern and western parts of France.

The most valuable and extensive beds of coal which have been found and wrought, are in Great Britain. The general form of our great independent coal-beds, is semi-circular, or semi-elliptical, being the segment of a great basin. The strata have a dip or declination to the horizon of from 1 in 5, to 1 in 20. They are rarely vertical, and seldom perfectly horizontal to any considerable extent. Slips and dislocations of the strata, however, derange more or less the general form.

Professor Jameson has divided this most useful mineral into the following species and subspecies:

Species 1. Brown coal.

Species 2. Black coal, of which there are four sub-species; slate coal, cannel coal, foliated coal, and coarse coal.

1. Slate coal. Its color is intermediate between velvet-black, and dark grayish-black. It has sometimes a peacock-tail tarnish. It occurs massive, and in columnar and egg-shaped concretions. It has a resinous lustre. Principal fracture slaty; cross fracture imperfect, conchoidal. Harder than gypsum, but softer than calcareous spar. Brittle. Sp. gr. 1.26 to 1.38. It burns longer than cannel coal; cakes more or

2. Cannel coal. Color between velvet and grayish-black. Massive. Resinous lustre. Fracture flat-conchoidal, or even. Fragments trapezoidal. Hardness as in the preceding sub-species. Brittle. Sp. gr. 1.23 to 1.27 It occurs along with the preceding. It is found near Whitehaven, at Wigan, in Lancashire, Brosely, in Shropshire, near Sheffield; in Scotland, at Gilmerton and Muirkirk, where it is called parret coal. It has been worked on the lathe into drinking vessels, snuff boxes, &c.

3. Foliated coal. Its color is velvet-black, sometimes with irridescent tarnish. Massive, and in lamellar concretions. Resinous or splendent lustre; uneven fracture; fragments approaching to trapezoidal. Softer than cannel coal; between brittle and sectile. Easily broken. Sp. gr. 1:34 to 14. The Whitehaven variety consists, by Kirwan, of 57 carbon, 41-3 bitumen, and 17 ashes. It occurs in the coal formations of this and other countries. It is distinguished by its lamellar concretions, splendent lustre, and easy frangibility.

4. Coarse coal. Color dark grayish-black, inclining to brownish-black. Massive, and in granular concretions. Glistening lustre. Fracture imperfect, scaly. Fragments indeterminate, angular. Hardness as above. Easily frangible. Sp. gr. 1.454. It occurs in the German coal formations. To the above, Professor Jameson has added soot-coal; which has a dark grayishblack color; is massive; with a dull semi-metallic lustre. Fracture uneven; sometimes earthy. Shining streak; soils; is soft, light, and easily frangible. It burns with a bituminous smell, cakes, and leaves a small quantity of ashes. It occurs along with slate-coal in West-Lothian and the Forth district; in Saxony and Silesia.

Species 3. Glance-coal, of which the Professor gives two sub-species, pitch-coal and glance-coal. 1. Pitch-coal. Color velvet-black. Massive, or in plates and botroidal branches, with a woody texture. Splendent and resinous. Fracture, large perfect conchoidal. Fragments sharp-edged and indeterminate angular; opaque; soft; streak brown-colored. Brittle. Does not soil. Sp. gr. 1.3. It burns with a greenish flame. It occurs along with brown coal in beds, in floetz, trap, and limestone rocks, and in bituminous shale. It is found in the Isles of Sky and Faroe, in Hessia, Bavaria, Bohemia, and Stiria. It is used for fuel, and for making vessels and snuff-boxes. It is called black amber in Prussia, and is cut into rosaries and necklaces. It is distinguished by its splendent lustre and conchoidal fracture. It was formerly called jet, from the river Gaga in Lesser Asia.

2. Glance-coal; of which we have four kinds,

Slaty glance-coal. Color iron-black. Massive. Lustre shining, and imperfect metallic. Principal fracture slaty; coarse fracture imperfect conchoidal. Fragments trapezoidal. Softer than conchoidal glance-coal. Easily frangible; between sectile and brittle. Sp. gr. 1.50. It burns without flame or odor. It consists, by Dolomieu, of 72.05 carbon, 13-19 silica, 3-29 alumina, 3:47 oxide of iron, and 8 loss. It occurs in beds or veins of different rocks. In Spain in gneiss; in Switzerland in mica-slate and clay-slate; in the trap rock of the Calton-hill, Edinburgh; in the coal formations of the Forth district. It is found also in the floetz districts of Westcraigs, in West Lothian, Dunfermline, Cumnock, Kilmarnock, and Arran; in Brecknock, Caermarthenshire, and Pembrokeshire, in England; and at Kilkenny, Ireland; and abundantly in the United States: In this country it is called blind coal.

Columnar glance-coal. Color velvet-black and grayish-black. Massive, disseminated, and in prismatic concretions. Lustre glistening, and imperfect metallic. Fracture conchoidal. Fragments sharp-edged. Opaque. Brittle. Sp. gr. 1.4. It burns without flame or smoke. It forms a bed several feet thick in the coal-field of Sanquhar, in Dumfries-shire; at Saltcoats, in Ayrshire, it occurs in beds and in green-stone; in basaltic columnar rows near Cumnock in Ayrshire.

Fibrous coal. Color dark grayish-black. Massive, in thin layers, and in fibrous concretions. Lustre glimmering, or pearly. It soils strongly. It is soft, passing into friable. It burns without flame; but some varieties scarcely yield to the most intense heat. It is met with in the different coal-fields of Great Britain. Its fibrous concretions and silky lustre distinguish it from all the other kinds of coal.

It is not certain that this mineral is wood mineralised. Several of the varieties may be original carbonaceous matter, crystallised in fibrous concretions.

Parts

3.7 10.0

Charcoal. Earth. 100 Kilkenny coal, he says, contain 97.3 Anthracite Ditto Ditto

90.0

72.0 20.0 97.25 2.7

Coal of Notre Dame de Vaux, 78.5 20.

We add, from the Philosophical Magazine, Mr. Mushet's general table of the analyses of different kinds of pit-coal, in carbonisation.

COAL-MINES, BRITISH. It is, generally agreed, that our cannel coal is the lapis ampelites of the Romans; though it seems to have been used by them only for making toys, brace lets, &c. But of that common fuel which we denominate coals, the native Romans were entirely ignorant. It is certain that they are not, as some have imagined, the lapis obsidianus of Pliny, about which there have been great disputes, and of which four statues of elephants were made, and placed in the temple of Concord by Augustus nor the gagates, or jet, which others, again, have taken for the lapis obsidianus; though the lightness and texture show plainly that it is not either stone or coal. In fact there are no beds of it in the compass of Italy. The great line of that fuel seems to sweep away round the globe, from north-east to south-west, not ranging at a distance even from the south-east parts of our island, as is generally imagined, but actually visiting Brabant and France, and yet avoiding Italy. The primæval Britons appear to have used it; and in the precincts of Manchester particularly, which are furnished with an inexhaustible abundance of it, they could not have long remained unapprised of the useful combustible around them. The currents there frequently bring down fragments of coal from the mountains; and in the long and winding course of them through the parish the Britons would soon mark the shining stones in the channels; and by the aid of accident, or the force of reflection, find out the utility of them. But we can advance still nearer to a certainty. Several pieces of coal were discovered some years ago in the sand under the Roman way to Ribchester, when both were dug up at the construction of a house in Quaystreet. The number of pieces, several of them as large as eggs, was not less than forty; and a quantity of slack was dug up with them. These circumstances show the coals to have been lodged on the spot, before the road of the Romans covered it. That ground being in the neighbourhood of Mancenion, the Britons had there deposited a quantity of coals, probably for the use of the garrison, and many of the smaller fragVOL. VI.

ments, and some of the slack, were buried in the sand upon which they were laid. And that the Britons, in general, were acquainted with this fuel, is evident from its appellation amongst us at present, which is not Saxon, but British; and subsists among the Irish in their O-gual, and among the Cornish in their kolan, to this day. The extensive coal-mines, therefore, with which the kingdom of England and the precincts of Manchester are so happily stored, were first noticed by the skill, and first opened by the labor, of the Britons; and some time before the arrival of the Romans among us. And the nearer quarries in the confines of Bradford, Newton, and Manchester, would naturally attract the notice, and invite the enquiries of the Britons, before any others. The current of the Medlock, which washes the sides of them, would bring down specimens of the riches within, lodge many of them about the Castlefield, and allure the Britons successively to a collection of the one and a search after the other. But, for two ages after the discovery, wood continued to compose the general firing of the nation. In 852 a grant was made of some lands by the abbey of Peterborough, under the reservation of certain boons and payments in kind to the monastery; as, one night's entertainment; ten vessels of Welsh, and two of common ale; sixty cart-loads of wood, and twelve of pit coal; where we see the quantity of coal was only one cart-load to five of wood. The latter naturally continued the principal article of our fuel, as long as the forests and thickets presented themselves so readily to the hand and such it continued till a very late period. The first public notice of the former is mentioned by Mr. Hume to have been in the time of Henry III. who, in the year 1272, granted a charter to the town of Newcastle, giving the inhabitants a licence to dig coals, and the first statute relating to this article was in the 9 Henry V. c. 10; ordering all keels in the port of Newcastle to be measured by commissioners, before carriage of coals, on pain of forfeiture. They were not brought into common use till the reign of Charles I., and were then sold for about 17s. a chaldron,

G