* GLINKSTONE. A stone of an imperfectly slaty structure, which rings like metal when struck with a hammer. Its colour is gray of various shades; it is brittle; as hard as feldspar, and translucent on the edges. It occurs in columnar and tabular concretions. Sp. gr. 2.57. Fuses easily into a nearly colourless glass. Its constituents are 57.25 silica, 25.5 alumina, 2.75 lime, 8.1 soda, 3.25 oxide of iron, 0.25 oxide of manganese, and 3 of water.Klaproth. This stone generally rests on basalt. It occurs in the Ochil and Pentland hills, the Bass-rock, the islands of Mull, Lamlash, and Islay, in Scotland; the Breidden hills in Montgomeryshire, and in the Devis Mountain, in the county of Antrim. It is found in Upper Lusace and Bohemia.

• CLINOMETER. An instrument for measuring the dip of mineral strata. It was originally invented by R. Griffith, Esq. Professor of Geology to the Dublin Society, and subsequently modified by Mr. Jardine and Lord Webb Seymour. See a description and drawing by the latter, in the third volume of the Geological Transactions. Lord Webb's instrument was a very perfect one. It was made by that unrivalled artist, Mr. Troughton..

• CLOUD. A mass of vapour, more or less opaque, formed and sustained at considerable heights in the atmosphere, probably by the joint agencies of heat and electricity. The first successful attempt to arrange the diversified forms of clouds, under a few general modifications, was made by Luke Howard, Esq. We shall give here a brief account of his ingenious classification.

The simple modifications are thus named and defined. 1. Cirrus. Parallel, flexuous, or diverging fibres, extensible in any or in all directions. 2. Cumulus. Convex or conical heaps, increasing upwards from a horizontal base. 3. Stratus. A widely extended, continuous horizontal sheet, increasing from below.

The intermediate modifications which require to be noticed are, 4. Cirro-cumulus. Small well-defined roundish masses, in close horizontal arrangement. 5. Cirrostratus. Horizontal, or slightly inclined masses, attenuated towards a part or the whole of their circumference, bent downward, or undulated, separate or in groups, consisting of small clouds having these characters.

The compound modifications are, 6. Cumulo-stratus. The cirro-stratus, blended with the cumulus, and either appearing intermixed with the heaps of the latter, or superadding a wide-spread structure to its base.

7. Cumulo-cirro-stratus, vel Nimbus. The rain cloud. A cloud or system of clouds

from which rain is falling. It is a horizontal sheet, above which the cirrus spreads, while the cumulus enters it laterally and from beneath.

The cirrus appears to have the least density, the greatest elevation, the greatest variety of extent and direction, and to appear earliest on serene weather, being indicated by a few threads pencilled on the sky. Before storms they appear lower and denser, and usually in the quarter opposite to that from which the storm arises. Steady high winds are also preceded and attended by cirrus streaks, running quite across the sky in the direction they blow in.

The cumulus has the densest structure, is formed in the lower atmosphere, and moves along with the current next the earth. A small irregular spot first appears and is as it were the nucleus on which they increase. The lower surface continues ir. regularly plane, while the upper rises into conical or hemispherical heaps; which may afterwards continue long nearly of the same bulk, or rapidly rise into mountains. They will begin, in fair weather, to form some hours after sunrise, arrive at their maximum in the hottest part of the afternoon, then go on diminishing and totally disperse about sunset. Previous to rain, the cumulus increases rapidly, appears lower in the atmosphere, and with its surface full of loose fleeces or protuberances. The formation of large cumuli to leeward in a strong wind, indicates the approach of a calm with rain. When they do not disappear or subside about sunset but continue to rise, thunder is to be expected in the night. The stratus has a mean degree of density, and is the lowest of clouds, its inferior surface commonly resting on the earth or water. This is properly the cloud of night, appearing about sunset. It com. prehends all those creeping mists which in calm weather ascend in spreading sheets (like an inundation of water), from the bottom of valleys, and the surfaces of lakes and rivers. On the return of the sun, the level surface of this cloud begins to put on appearance of cumulus, the whole at the same time separating from the ground. The continuity is next destroyed, and the cloud ascends and evaporates, or passes off with the appearance of the nascent cumulus. This has long been experienced as a prognostic of fair weather.

The cirrus having continued for some time increasing or stationary, usually passes either to the cirro-cumulus or the cirro-stratus, at the same time descending to a lower station in the atmosphere This modification forms a very beautiful sky; is frequent in summer, an attendant on warm and dry weather. The cirro-stratus, when seen in the distance, frequently gives the

idea of shoals of fish. It precedes wind and rain; is seen in the intervals of storms; and sometimes alternates with the cirrocumulus in the same cloud, when the dif. ferent evolutions form a curious spectacle. A judgment may be formed of the weather likely to ensue by observing which modification prevails at last. The solar and lunar halos, as well as the parhelion and paraselene, (mock sun and mock moon), prognostics of foul weather, are occasioned by this cloud. The cumulo-stratus precedes, and the nimbus accompanies rain.

See RAIN.

Mr. Howard gives a view of the origin of clouds, which will be found, accompanied with many useful remarks, in the 16th and 17th volumes of the Philos. Magazine.* CLYSSUS. A word formerly used to denote the vapour produced by the detonation of nitre with any inflammable sub

stance.

COAK. Coal is charred in the same manner as wood to convert it into charcoal. An oblong square hearth is prepared by beating the earth to a firm flat surface, and puddling it over with clay. On this, the pieces of coal are piled up, inclining toward one another, and those of the lower strata are set up on their acutest angle, so as to touch the ground with the least surface possible. The piles are usu from 30 to 50 inches high,

usually

16

feet broad, and contain from 40 to 100 tons of coal. A number of vents are left, reaching from top to bottom, into which the burning fuel is thrown, and they are then immediately closed with small pieces of coal beaten hard in. Thus the kindled fire is forced to creep along the bottom, and when that of all the vents is united, it rises gradually, and bursts out on every side at once. If the coal contain pyrites, the combustion is allowed to continue a considerable time after the disappearance of the smoke, to extricate the sulphur, part of which will be found in flowers on the surface: If it contain none, the fire is covered up soon after the smoke disappears, beginning at the bottom, and proceeding gradually to the top. In 50, 60, or 70 hours, the fire is in general completely covered with the ashes of char formerly made, and in 12 or 14 days the coak may be removed for use. In this way a ton of coals commonly produces from 700 to 1100 pounds

of coak.

In this way the volatile products of the coal, however, which might be turned to good account, are lost: but some years ago, Lord Dundonald conceived and carried into effect, a plan for saving them. By burning the coal in a range of 18 or 20 stoves, with as little access of air as may be, at the bottom; and conducting the smoke, through proper horizontal tunnels,

to a capacious close tunnel 100 yards or more in length, built of brick, supported on brick arches, and covered on the top by a shallow pond of water; the bitumen is condensed in the form of tar: 120 tons of coal yield about 3 of tar, though some coals are said to be so bituminous as to afford 1-8th of their weight. Part of the tar is inspissated into pitch, 21 barrels of which are made of 28 of tar; and the volatile parts arising in this process are condensed into a varnish, used for mixing with colours for out-door painting chiefly. A quantity of ammonia too is collected, and used for making sal ammoniac. The cakes thus made are likewise of superior quality.

* COAL. This very important order of combustible minerals, is divided by Professor Jameson into the following species and sub-species:

Species 1. Brown coal, already described. Species 2. Black coal, of which there are four sub-species, slate coal, cannel coal, foliated coal, and coarse coal.

1. Slate coal. Its colour is intermediate between velvet-black, and dark grayishblack. 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 less, and leaves a slag. The constituents of the slate coal of Whitehaven, by Kirwan, are 56.8 carbon, with 43.2 mixture of asphalt and maltha, in which the former predominates. This coal is found in vast quantities at Newcastle; in the coal formation which stretches from Bolton, by Allonby and Workington, to Whitehaven. In Scotland, in the river district of Forth and Clyde; at Cannoby, Sanquhar, and Kirconnel, in Dumfries-shire; in Thuringia, Saxony, and many other countries of Germany. It sometimes passes into cannel and foliated coal.

2. Cannel coal. Colour 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 Gil merton 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 colour is velvet. black, sometimes with iridescent tarnish. Massive, and in lamellar concretions. Re. sinous or splendent lustre; uneven fracture, fragments approaching to trapezoidal. Softer than cannel coal; between brittle and sectile. Easily broken. Sp. gr. 1.34 to 1.4. The Whitehaven variety consists, by Kirwan, of 57 carbon, 41.3 bitumen; and 1.7 ashes. It occurs in the coal formations of this and other countries. It is distinguish ed by its lamellar concretions, splendent lustre, and easy frangibility.

4. Coarse coal. Colour dark, grayishblack, inclining to brownish-black. Massive, and in granular concretions. Glisten. ing 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 colour; is massive; with a dull semimetallic 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 3d. Glance-coal, of which the Professor gives two sub-species, pitch-coal, and glance-coal. 1. Pitch-coal. Colour velvet-black. Massive, or in plates and botrioidal branches, with a woody texture. Splendent and resinous. Fracture, large perfect conchoidal. Fragments sharp-edged and indeterminate angular; opaque; soft; streak brown coloured. 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, conchoidal, slaty, columnar, and fibrous. The conchoidal has an iron-black colour, inclining to brown, with sometimes a tempered steel-varnish. Massive and vesicular. Splendent, shining and imperfect metallic lustre. Fracture flat-conchoidal; fragments sharp-edged. Hardness as above. Brittle, and easily frangible. In thin pieces, it yields a ringing sound. It burns without flame or smell, and leaves a white coloured ash. Its constituents are 96.66 inflammable matter, 2 alumina, and 1.38 silica and iron. It occurs in beds in clay-slate, graywacke, and alum-slate; but it is more abundant in secondary rocks, as in coal and trap formations. It occurs in beds in the

coal formations of Ayrshire, near Cumnock and Kilmarnock; in the coal district of the Forth; and in Staffordshire. It appears to pass into slaty glance-coal.

Slaty glance-coal. Colour iron-black. Massive. Lustre shining, and imperfect metallic. Principal fracture slaty; coarse fracture imperfect conchoidal. Fragments trapezoidal. Softer than conchoidal glancecoal. Easily frangible; between sectile and brittle. Sp. gr. 1.50. It burns without flame or odour. 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 in different rocks. In Spain, in gneiss; in Switzerland, in mica-slate and clay-slate; in the trap rock of the Caltonhill, 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. Colour velvet-black and grayish-black. yish-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 greenstone; in basaltic columnar rows near Cumnock, in Ayrshire.

Fibrous coal. Colour 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 coalfields of Great Britain. Its fibrous concre tions and silky lustre distinguish it from all the other kinds of coal.

It is not certain that this mineral is wood mineralized. Several of the varieties may be original carbonaceous matter, crystallized in fibrous concretions.-Jameson.

It was remarked long ago by Macquer, 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 13 parts of dry wood-charcoal decompose 100 of nitre.

100 parts. Charcoal. Bitumen. Earth. Sp.gr. Kilkenny coal, 97.3 0 3.7 1.526 Comp.cannel, 75.2 21 68 maltha 3.1 1.232

Swansey, 73.53 23.14 mixt.

3.33 1.357

Leitrim,

Wigan,

71.43 23.37 do. 61.73 36.7 do.

Newcastle, 58.00 40.0 do. Whitehaven 57.0 41.3

1.271

1.7 1.257

Slaty-cannel, 47.62 32.52 mal. 20.0 1.426 Asphalt, 31.0 68.0 bitumen -1.117 Maltha,

8.0

2.07

1.150

swers best for giving great heats in a wind furnace, as in distillation on the great scale; and glance coal is used for drying grain and malt. The coals of South Wales contain less volatile matter than either the English or the Scotch; and hence, in equal weight, produce a double quantity of cast iron in smelting the ores of this metal. It is supposed that 3 parts of good Newcastle coals, are equivalent as fuel to 4 parts of good Scotch coals.

Werner has ascertained three distinct coal formations, without including the beds of coal found in sandstone and limestone formations. The first or oldest formation, he calls the independent coal formation, because the individual depositions of which it is composed, are independent of each other, and are not connected. The second is that which occurs in the newest floetztrap 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 would 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 coal, and slaty glance coal. The latter was first found in this formation in Arran, Dumfries-shire, Ayrshire, and at Westcraigs, by Professor 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 sand

stone, marl, limestone, porphyritic stone, bituminous shale, clay-ironstone; and as discovered by Professor Jameson, greenstone, amygdaloid, and graphite. The slate-clay is well characterized, by the great variety of vegetable impressions of such plants as flourish in marshes and woods. The smaller 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 superincum bent 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 coal mines 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.

By far 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 coalbeds, 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 of the basin.

Those who wish to understand the most improved modes of working coal mines, will be amply gratified by consulting, A Report on the Leinster Coal District, by Richard Griffith, Esq. Professor of Geology, and Mining Engineer to the Dublin Society. The author has given a most luminous view of Mr. Buddle's ingenious system of working and ventilating, in which from 7-8ths to 9-10ths of the whole coal may be raised; instead of only, which was the proportion obtained in the former

modes. Mr. Griffith has since published

some other reports, the whole constituting an invaluable body of mining information.* COAL GAS. When coal is subjected in close vessels to a red heat, it gives out a vast quantity of gas, which being collected and purified, is capable of affording a beautiful and steady light, in its slow combustion through small orifices. Dr. Clayton seems to have been the first who performed this experiment, with the view of artificial illumination, though its application to economical purposes was unaccountably neglected for about 60 years, At length Mr. Murdoch of the Soho Foundry, instituted a series of judicious experiments on the extraction of gas from ignited coal; and succeeded in establishing one of the most capital improvements

which the arts of life have ever derived from philosophical research and sagacity.

In the year 1798, Mr. Murdoch, after several trials on a small scale five years before, constructed at the Foundry of Messrs. Bolton and Watt, an apparatus upon a large scale, which during many successive nights was applied to the lighting of their principal building; and various new methods were practised of washing and purifying the gas. In the year 1805, the cotton mill of Messrs. Philips and Lee, reckoned the most extensive in the kingdom, was partly lighted by gas under Mr Murdoch's direction; and the light was soon extended over the whole manufactory. In the same year, I lighted up the large lecture-room of Anderson's Institution with coal-gas, generated in the laboratory; and continued the illumination every evening through that and the succeeding winter. Hence I was induced to pay particular attention to the theory and practice of its production and use.

bright cherry-red

If coal be put into a cold retort, and slowly exposed to heat, its bitumen is merely volatilized in the state of condensible tar. Little gas, and that of inferior illuminating power, is produced. This distillatory temperature may be estimated at about 600° to 700° F. If the retort be previously brought to a heat, then the coals, the instant after their introduction, yield a copious supply of good gas, and a moderate quantity of tarry and ammoniacal vapour. But when the retort is heated to nearly a white incandescence, the part of the gas richest in light, is attenuated into one of inferior quality, as I have shown in detailing Berthollet's experiments on CARBURETTED HYDROGEN. A pound of good cannel coal, properly treated in a small apparatus, will yield five cubic feet of gas, equivalent in illuminating power to a mould candle, six in the pound. See CANDLE.

On the great scale, however, 35 cubic

feet of good gas are all that should be ex

pected from 1 pound of coal. A gas jet, which consumes half a cubic foot per hour, affords a steady light equal to that of the above candle.

According to Mr. Murdoch's statement, presented to the Royal Society, 2500 cubic feet of gas were generated in Mr. Lee's retort from 7 cwt. 784 lbs. of cannel coal. This is nearly 3 cubic feet for every pound of coal, and indicates judicious management. The price of the best Wigan cannel is 13 d. per cwt. (228. 6d. per ton) delivered at Mr. Lee's mill at Manchester; or about 88. for the seven hundred weight. About of the above quantity of of good common coal at 10s. per ton, is required for fuel to heat the retorts. Near