USEFUL MINERALS. 



*s probably, besides this ascertained quantity, a 

 considerable extent of sub-Permian coal-seams 

 not yet proved. It appears, too, that, in the 

 opinion of many eminent geologists, coal is not 

 unlikely to be found at depths not exceeding 1200 

 .feet, under the chalk and other newer formations 

 in the south of England coal-seams having been 

 tfound under these strata across the Channel, not 

 <far from Calais. 



Taking into account the coal which probably 

 ^exists under the Permian, New Red Sandstone, 

 and other superincumbent strata in the United 

 Kingdom, the coal commissioners increase their 

 estimate of the quantity still available for use to 

 146,480 millions of tons. In 1881 Dr Hull 

 corrected the figures to date, giving a total avail- 

 able supply of 136,000 million tons, sufficient, in 

 his estimate, to last for a thousand years (the coal 

 harvest of 1880 being 147,000,000 tons). On the 

 other hand, some authorities assert that, owing to 

 increase in population, and the increasing con- 

 sumption of coal in manufactures, about 100 years 

 will suffice to exhaust them. Between this and 

 the other extreme of about 1000 years, formed on 

 the assumption that hereafter the population of 

 the country will but slightly increase, there are 

 innumerable conjectures and estimates. 



On the continent of Europe, productive coal- 

 Ifields occur in Belgium, France, various parts of 

 Northern Germany, Spain, and Russia. By far 

 the largest in area are those of Russia, and they 

 are known to contain many valuable beds of coal, 

 although as yet comparatively little has been 

 worked. Coal is also found in India, China, 

 Japan, and the Malayan Archipelago, in Aus- 

 tralia and New Zealand, and in Africa. Turning 

 to the New World, there is evidence of promising 

 -coal-deposits in several South American countries, 

 but, owing to the great supply of wood in their 

 forests, there is little temptation to work them. 

 In Canada, Nova Scotia, New Brunswick, and 

 Newfoundland, there are small, though valuable 

 .coal-fields ; but, in the United States, by far the 

 largest fields of fossil fuel in the world are found. 

 The entire area of these is about 200,000 square 

 miles, being 38 times greater than the area of 

 the coal-fields of Great Britain. But although 

 the coal-measures of the States are of vast extent, 

 and contain many valuable coal-seams a few of 

 them 40 and even 50 feet thick at certain places 

 it has been doubted by some shrewd observers 

 whether the amount of workable coal in them is 

 not greatly exaggerated by American writers. In 

 proportion to the extent of the seams, the quan- 

 tity of coal annually raised in the States is small, 

 being only about 70,000,000 tons. 



In what has been already said, no notice has 

 been taken of fuel found in formations other than 

 v the coal-measures. True coal, however, occurs in 

 the Oolite at Brora in Sutherland, in Skye, York- 

 shire, and Pennsylvania, and that found in Aus- 

 tralia appears to belong to formations both older 

 -and newer than the Carboniferous. Nor should 

 we omit to mention a substance called brown 

 coal or lignite, of which large deposits occur in 

 the Wealden, Chalk, Eocene, and Miocene of 

 North Germany, Austria, and Italy. This mineral, 

 which often retains its woody structure in a nearly 

 perfect state, is of less value than true coal, but 

 still it is of great importance as a fuel to the 

 -districts where it is found. A few years ago, 



about 5,000,000 tons of it were raised in one year 

 in Prussia alone. 



Coal-mining is in some districts a comparatively 

 simple operation ; but in regions where the strata 

 are troubled, where fire-damp is prevalent, and 

 where the workings are deep, much care and skill 

 are required in conducting it. A seam of coal 

 scarcely ever lies in a horizontal position it is 

 nearly always inclined, and sometimes at a very 

 high angle. Suppose, then, we were to begin to 

 work a coal-seam from the ' outcrop ' downwards, 

 we could not take it out to any great depth with- 

 out being stopped by the accumulation of water ; 

 and on account of this difficulty, no attempt was 

 made, in the early days of coal-mining, to work 

 deeper than could be done in the fashion of an 

 open quarry. Next came the plan of driving in a 

 tunnel, called a day-level, from the lowest point, 

 on, say, a sloping hill-side, till it reached the coal- 

 seam. This served as a drain, and allowed all the 

 coal above that level to be worked out In later 

 times, and in situations where a day-level was not 

 practicable, an inclined tunnel or gallery was some- 

 times made, with wooden lift-pumps at certain 

 distances to remove the water. Sometimes, again, 

 it was removed in barrels wound up vertical 

 shafts 30 or 40 fathoms deep. Coal was brought 

 to the surface by methods equally primitive. 

 Some pits were fitted with ladders, up which 

 women carried the coal on their backs in baskets, 

 and this, too, occasionally from a depth of 50 or 

 60 fathoms. In other places, boys, and women as 

 well, drew it in small four-wheeled trams along 

 sloping galleries to the surface, or along levels to 

 the bottom of a shaft, to be hoisted by a windlass 

 in tubs to the mouth of the pit. 



By successive steps from these rude modes of 

 mining, some of them here and there still in use, 

 we come to the method practised at the present 

 day in many of the larger English collieries. A 

 few of these are noble specimens of underground 

 engineering. The shaft is sunk in more than one 

 instance at a cost of nearly one hundred thousand 

 pounds to the lowest point of the coal-seam 

 which can be practically reached ; and this is in 

 some cases about two thousand feet deep. From 

 the bottom of this, galleries, called levels, are 

 driven in several directions, sometimes one or 

 even two miles in length. These have just enough 

 of rise to allow water to flow back to the sump or 

 lodgment at the bottom of the shaft, into which 

 the pumps dip. From the levels, other roads are 

 driven in different directions, and if the seam is 

 thin, say under four feet, then the whole of the 

 coal is removed as the colliers proceed. This is 

 called the long-wall system. If it is thick, then 

 pillars or stoops are left at regular distances, and 

 between them the coal is worked out. In this 

 way, the ground-plan of a mine becomes not 

 unlike that of a forest with thick square dumpy 

 pillars instead of round trees. This is variously 

 called the post-and-stall, board-and-pillar, and 

 stoop-and-room system. A large and powerful 

 steam-engine is, of course, required to raise the 

 coal from such depths, and to pump out the water 

 which rapidly accumulates in all underground 

 operations. One of these engines will raise a 

 cage loaded with thirty-six hundredweight of coal, 

 fourteen hundred feet in a minute, bringing to the 

 surface about a thousand tons a day. 



The proper ventilation of a coal-mine is a 



387 



