326: On the Coal Trade.[May

Tam about to aſſert, that of real fuel, of a@ual carbon, moſt ex- ts in the inferior coal. The coal, termed bef coal in London, ought rather to be called round coal, from the larger lumps which find their way to London, after all:the ſhiftings and toſlings they experience in the pit, the coal-waggon, the ſteath, the Tyne keels, the ſhipping, the Thames lighter, the wharf, and the final loading and ſhooting. Of the formation of coal, I am not com- petent to give a chemical account, nor do I accurately know its analyſis: 1 have learnt, however, from caſual information, that the philoſophers of the day have ſettled, that coal is formed in the earth from frata of decayed timber, left there in ſome an- cient deluge of our planet. So that peat may be reckoned incep- tive. coal, which wants only circumſtance to its perfe@tion,— ‘This circumſtance, is probably, a bitumenous ſpring; ſuch a one as has been aually diſcovered, and now furniſhes tar from under the coal ſtratum in Colebrook dale. i

But ſubterraneous ſprings convey very various matter, and the very rocks and ſtones, indicate by their fifſures and petrifactions, that they were once in a fluid ſtate.— Thus, when the bitume- noué matter(ex-ſuding from the ſubterraneous ſtratum of‘fallen pines) was mixed in its progreſs with pure water, the moiftened timber in its decay could imbibe and retain bitumen only; when the water chanced to be flicious, inſtead of pure coal, either ſlate, or at leaſt, harſh untraétable coal was eſtabliſhed in the earth; and the weighable coal of Scotland and Staffordſhire was thus formed. All the gradations betwixt coal and ſlate muſt be fami- © liar to thoſe who have been accuſtomed to a coal-fire,—from the ſlate, which a moderate torrefaction leaves white, hard and heavy; to the pure ſmall coal from Newcaſtle, which, forming cinders (by an imperfe& fuſion) burns with laſting heat, and leaves Ícarce any remnant except the ſoot in the chimney. Of this ſort, is made the coke which conveys the carbonic principle to’the iron ore in the foundery; and only management is reguired to make it as-convenient as the round coal, even for houſe conſumption. This management conſiſts, in remembering to take off ſome well-caked cinders overnight, for the purpoſe of lighting the fre in the morning, and alſo, in never letting the fire down very low in the day time 5 leſt the throwing ſmall coalon a weak fire ſhould ſtop the paſſage of air, and ſv extinguiſh the fire. This ſmall coal(in the language of the collieries) is calléd culm, and is there held of no value ¿ becauſe it cannot be exported. If al! the coal was. not ſent from the pit in lumps, it would be ad duſt be- fore it arrived in London.

The moſt ſimple rule of diſtinguiſhing good, ftrong, laſting coal, is its fragility; that is, the cafe with which it breaks when ſtruck. Hence it may be ſeen, that(generally ſpeaking) the largeſt coal muſt be the worſt; becauſe, after taking the ſame toſſing and ſifting, more of it remains unbroken. However