In these deep and extensive works, the greatest care is requisite to keep them continually ventilated with perpe tual currents of fresh air, to expel the damps and other noxious exhalations, and supply the miners with a sufficiency of that vital fluid. In the deserted works, large quantities of these damps are fre quently collected, and often remain for a long time without doing any mischief: but when, by some accident, they are set on fire, they produce dreadful and de structive explosions, and burst out of the pits with great impetuosity, like the.fiery eruptions from burning mountains. The coal in these mines hath several times been set on fire by the fulminating damp, and continued burning many months, until large streams of water were conducted into the mines, and suffered to fill those parts where the coal was on fire. Several collieries have been entirely destroyed by such fires : of these there are instances near Newcastle, and in other partsofEng land, and in the shire of Fife in Scotland ; in some of which places the fire has conti nued burning for ages. To prevent as much as Ossible the collieries from being filled with these pernicious damps, it has been found necessary to search for those crevices in the coal whence they issue, and then confine them within a narrow space, from which they are afterwards conducted through long tubes into the open air,where, being set on fire, they consume in perpe tual flames, as they continually arise out of the earth. The late Mr. Spedding, who was the great engineer of those works, having observed that the fulminating damp could only be kindled by flame, and was not liable to be set on fire by red hot iron, nor by the sparks produced by the colli sion of flint and steel, invented a machine, in which, while a steel wheel is turned round with a very rapid motion, flints are applied to it, and, by the abundance of fiery sparks emitted, the miners are ena bled carry on their work in places where the flame of a lamp or candle would occasion dreadful explosions. Without some intervention of this sort, the work ing of these mines would long ago have been impracticable, so greatly are they annoyed by these inflammable damps. Fewer mines, however, have been ruined by fire than by inundations ; and here that noble piece of mechanism the steam-en gine displays its beneficial effects. When the four engines belonging to this colliery are all at work, they discharge 1228 gal lons ol water every minute at thirteen strokes; and, after the same rate, 1,768,320 gallons every twenty-four hours.
The road from the Whitehaven coal mines to the water side is mostly on a gentle descent, and provided with an iron railway : this, by removing much of the friction, exceedingly facilitates the carri age of the coals to the shipping, which are laid alongside of the quay to receive them. When the waggons are loaded, they run without any assistance on the railway till they arrive at the quay, where the bottom striking out, the waggon dis charges its contents into a large flue, or, as the workmen term it, a hurry, through which it rattles into the hold of the vessel with a noise like thunder. A man is placed in each waggon to guide it, who checks its progress, if necessary, by pressing down one of the wheels with a piece of wood provided for the purpose.
When the waggons are n loaded, they are carried round by a turn-frame, and drawn back to the pits by a single horse along another road. The coal trade is supposed to maintain nearly 15,000 mariners, mho employ about 2000 coal-heavers, who are allowed a fixed sum onclearing each ship., according to her tonnage. These are sup posed to be the hardest working men in the kingdom: they often earn six, seven, or eight shillings in the day ; of which at least one-third, or perhaps one half, is spent in porter. By a late act coals are permitted to be landed at Paddington, in the parish of Mary-le-bone, not, however, exceeding a specified quantity within the year. These coals come by the canals from the inland counties, generally in large masses and free from coal-dust. A patent has been granted within these rew years for the formation of coal-dust into balls, which are compacted by the admix ture of soft clay, tanner's bark, and various other materials, all of which tend to swell the mass and form a tolerable fuel : it brings much rubbish to an excellent use. A patent was also granted about twenty years back to Lard Dundonald for making tar from coal. This tar has been found to answer many useful purposes, being an admirable coating for wood or other work exposedto the weather; but, on account of its being peculiarly subtile, must be carefully kept away from articles of pro vision, to which it communicates a most unpleasant, bitiminous flavour. The cin ders and ashes from coal arc in much estimation, as a manure for soils, and are highly obnoxious to worms. They are likewise employed in the mak ing of bricks.
There are different opinions among geologists respecting time origin of coal. Some suppose this combustible substance to be produced by the decomposition of the soft parts of the immense quantity of organized bodies, of which we find almost every where the solid remains. But un fortunately this conjecture, which ap pears so natural, is liable to several strong objections. One is, the presence of vege tables scarcely decomposed, which are often met with in the middle of beds of coal. The others, the want of direct ex periments to prove that organized bodies give out bitumen during their decompo sition. Without stopping to discussthese points, we shall merely give the general conclusions of naturalists, as they are mentioned by Brogniart. 1. That coal was formed, either at the same time, or after the existence of organized bodies.
2. That this mineral when first formed was liquid, and of a great degree of purity.
3. That the cause which produces this deposit is several times renewed in the same place, and nearly under the same circumstances. 4. That the cause, what ever it may be, is nearly the same over all the earth, since the beds Of coal al ways exhibit nearly the same phenomena in their structure and accidental circum stances. 5. That these beds have not been .deposited by any violent revolu tion ; but, on the contrary, in the most tranquil manner ; since the organized bodies that are found in them are often entire, and the leaves of vegetables im pressed in the slate which covers the coals are hardly ever bruised or other wise deranged.