Coal has been discovered in more or less quantity in seventeen counties of Ireland. The Munster coal-district occupies a consi derable portion of the counties of Limerick and Kerry, and a large part of the county of Cork; it is by much the most extensive in Ireland. Coal and culm have been raised for near a century in the neighbourhood of Kan turk, in the county of Cork. At Droma,gh colliery the work has been carried on to a very considerable extent ; and the beds found in it are of four kinds, the Coal-Bed, the Bock Coal, the Bulk-Bed, and Bath's Bed. The greatest depth of the Munster collieries is about 80 yards.
On the continent of Europe coal-fields are very irregularly scattered. They occur abun dantly in Belgium. In Saxony and Bohemia coal is found; and in less quantity in Russia, Sweden, and Spain. France has many coal fields, but the produce is not enough for her consumption. There were 425 coal mines in France in 1844, of which however only 252 were worked, employing 30,000 persons.
Asia contains a little coal in China, Birmah, India, and Persia. Coal has been found abundantly both in Australia and Van Die men's Land. America, according to recent discoveries, seems to be richer in coal than any other part of the world.
Mr. Taylor, in his valuable ' Statistics of Coal,' says that the ascertained areas of the coal-fields of various countries are as fol lows : United States .. 133,138 sq. m.
British America ... 18,000 Great Britain ... 11,858 Spain 3,408 Prance 1119 Belgium ••• ... 518 But the actual yearly production, and bring ing to market, form a remarkably different series:— Great Britain ... 31,500,000 tons.
400,0110 United States ... 4,400,000 France ... 4.140,000 Prussia 3,500,000 Austria '" 700,000 Coal Mining.—The thickness of workable beds of coal may be said generally to vary from three or four to eight or nine feet, although sometimes, when several seams come together without any intervening layers of rock, they may expand to twenty or thirty feet, of which we have an example in the 'ten yard coal' of Staffordshire. In every coal field there are many seams of coal at greater or less intervals, one below another, of which as many as three or four are frequently worked in the same mine.
When the position of the beds of coal has been discovered, the first process is to sink a perpendicular shaft from the surface so as to intersect the various strata containing the coal, and of course as many of the beds of coal as are considered to be worth working.
The upper portion, as far down as the solid rock, is either bricked or walled, and where the ground is weak this casing may be conti nued throughout. On reaching the first work able seam of coal, the sinking of the pit is for a time suspended, and a broad straight passage termed a bord' or ' gate' is driven from it upon the seam of coal in opposite directions. The breadth of this passage is usually twelve or fourteen feet, and it is formed the whole height of the seam of coal, so as to expose the stratum above, which is called the 'roof,' and the one below, which is termed the thill,' and its direction is always arranged so as to follow the cleavage of the coal which forms its sides, which thus pre sents a clean uniform surface. When the principal bond has proceeded some distance on both sides of the pit, narrow passages, termed theadways; are driven from it at re gular intervals, and exactly at right angles ; and when these have proceeded eight or ten yards, they are made to communicate with another bord, which is opened parallel to the first and on each side of it. Thus the oper ations continue, until the mine resembles a town of streets rectangularly arranged. The water encountered in the above operations is drawn to the surface by a steam-engine erected at the top of the shaft, which is so arranged as also to raise the coal and rubbish, for which purpose either 'corves' or baskets are commonly employed. In small coal mines the ventilation is managed by separating a portion of the shaft from the larger part by an air tight boarding, which is carried down to the bottom ; but in large coal-mines another shaft is sunk at some distance from the first, and when the communication between them has been effected, the one being made downcast and the other upcast, the air is made to pass through the whole of the passages.
While the workings on the first seam of coal are thus going on, the shaft maybe sunk to a second or third seam, where similar ope • rations will be commenced, small under ground pits or 'staples' being sunk at inter vals from the workings on the upper seam to those on the seam below, by which ventilation will be promoted.