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hollow and would be extinguilhed if the topwere not broken in from time to time. Theproduce of allies is fmaller than in the freeburning coals, the greater part of them beingmixed with the carbonaceous part of the coaland forming grey fcorite, commonly known bythe name of cinders, which being burnt againwith frelh fuel give out an intenfe heat, and areflowly reduced, partly to heavy alhes and partlyto flag. The belt coal of NorthumberlandDurham and Yorkfhire is of this kind : it burnslonger and gives more heat than the preceding,and in general bears a higher price.

Slate coal is found principally in the indepen-dent coal-formation, and is the mod; widelydiffufed of any of the fpecies. It is often mixedwith pyrites, and penetrated by thin veins ofquartz or calcareous fpar.

Sp. VI. Pitch coal. Pechkohle , Werner.Houille piciforme, Broch.

Its colour is velvet black palling fometimesinto brownilh black. It occurs in mafs, inplates, and fometimes in the lhape of brancheswith a regular woody Itructure. It has a bril-liant refinous luftre, and a perfectly conchoidalfracture; the furfaces of the natural joints arenearly fpecular: its fragments are indeterminatelharp-edged. It is foft and brittle. Sp.gr. 1.3.

It burns with a greenilh flame and a ftrongbituminous fmell, and leaves behind a light yel-lowilh coloured alh. It occurs principally inthe neweft floetz-trap coal-formation. It is ufedas fuel, but the finer and harder pieces areworked into various trinkets, and go under thename of jet. It occurs in detached fragmentsin the Pruffian amber mines, and is there calledblack amber.

Sp. VII. Cannel coal. Kennelkohle, Werner.Houille de Kilkenny, Broch. (This mineralogifthowever is entirely in an error in fuppofingcannel and Kilkenny coal to be the fame, thelatter of thefe being a variety of Glance coal.See fpecies 8.)

Its colour is dark greyilh black. It occurs inmafs: has a gliftening refinous luftre. Its lon-gitudinal fradture is flat conchoidal, its crofsfracture is perfectly conchoidal. When cutwith a knife it exhibits a Aiming luftre, andthe cut furface is full of very minute conchoi-dal fractures, giving it a porous appearance.It is brittle, but is the moll difficultly frangibleof all the coals. Sp. g. 1.23. It is very inflam-mable, and crackles and flies while burning,efpecially if it J s no t ] a j c j j n t ] ie direction ofthe crofs fracture: it flames much and burnsquickly, but does not cake, and leaves behindfrom 3 to 4 per cent of allies.

The fplent coal of Scotland is an inferior va-riety of cannel: its principal fracture is flaty,its crofs fradture imperfectly conchoidal; itsfp. gr. 1.42. It contains pyrites, and leavesabout 21 per cent, of afhes.

Cannel coal occurs in the independent coal-formation. It is found in great plenty and re-markably pure at Wigan in Lancalhire, and oc-cafionally in molt of the other Englilh col-lieries.

The fplent coal abounds at Gilmerton, nearEdinburgh .

Its chief ufe is as a fuel, but the pureft Wigan cannel will bear to be worked in the turninglathe, from which it receives a high polilh:hence it is Ihaped into various ornamental uten-fils, and when cut into beads is not to be dif-tinguifhed from jet.

* * * Mineral Carbon . Deftitute of bitumen;confifts of charcoal, with various proportionsof earth and iron.

Sp. VII. Mineral charcoal. Mineralifche Holz-kohle. Werner.

Its colour is greyilh black. It occurs in platesand irregular pieces. It has a glimmering filkyluftre, and a fibrous fradture dil'covering its lig-neous texture. It foils the fingers, is foft andfriable. It is fomewhat heavier than commoncharcoal, and is eafily reduced to alhes beforethe blowpipe without flaming.

It occurs in thin layers in brown coal, Hatecoal, flaty glance coal, and pitch coal, but in toofmall quantities to be made any feparate ufeof.

Sp. VIII.. Glance coal.

Of this there are three varieties.

Var. 1. Conchoidal glance coal. Mufchlichglanzkohle, Werner. Houille eclatante , Broch.

Its colour is iron-black, inclining to brown.It occurs in mafs and veficular, the interior ofthe veficles has a fteel blue tarnilh. It has abright Ihining metallic luftre, and a perfectlyconchoidal fracture. Its fragments are inde-terminately angular, and lharp-edged. It ismoderately bard, frangible and light.

It burns without flame or fmell, and leaves awhite alh. That from Hefle has been analyzed,and contains 96.66 charcoal2. alumine1.33 oxyd of iron

99-99

It is of rare occurrence, having been met withonly in the Meiflner in Hefle, and at New-caitle.

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