CHAMBERS'S INFORMATION FOR THE PEOPLE. 



countries, for the manufacture of gas. The follow- 

 ing statistics will shew how remarkable has been 

 the increase in the produce of coal in Britain 

 since 1750, but it must be borne in mind that it 

 was not till 1854 that the coal statistics of the 

 country were carefully collected : 



Tons. 



Coal raised in 1750. 5,000,000 



1800 10,000,000 



1816 27,000,000 



1855 64,307,459 



ti 1870 110,431,192 



n 1884. 160,757,779 



Before giving the extent of our British coal- 

 fields, we shall first state how coal is believed to 

 have been formed, and what the leading kinds of 

 it are. True coal is scarcely obtained from any 

 other geological formation than that of the Car- 

 boniferous or coal-measures, where it occurs inter- 

 stratified with sandstone, shale, fire-clay, limestone, 

 ironstone, and other substances, the whole forma- 

 tion being one of remarkable economic import- 

 ance. Coal-seams vary in thickness from a few 

 inches up to thirty feet, the latter, however, being 

 rather an aggregate of several seams from which 

 intervening material has been washed away. 



Coal is undoubtedly formed of vegetable matter ; 

 its chemical composition, its microscopic struc- 

 ture, and the abundant remains of plants in it, all 

 prove this. The exact process by which it has 

 been formed has not been so clearly ascertained ; 

 nevertheless, in the opinion of most geologists, 

 our coal-seams are composed of plants which 

 grew in situ on the underclays always found imme- 

 diately beneath them. This is so far evident, from 

 the fact that the trunks of trees, called sigillaria, 

 occurring in the coal, have been found in some 

 instances actually connected with their roots, 

 termed stigmaria, in the underclay beneath it 

 As these underclays are all stratified, they must 

 have been formed under water ; and it is supposed 

 they were once the bottoms of shallow marshes, 

 estuaries, or lagoons, on which, under favourable 

 conditions of climate, a vegetation grew more 

 rank and luxuriant than that of any other geologi- 

 cal period before or since. By the constant decay 

 and renewal of forests on the same site, and per- 

 haps by the drifting of plants from other areas, 

 earned thither by currents, a great mass of vege- 

 table matter would at length accumulate. The 

 conversion of this into coal was no doubt effected 

 by the slow subsidence of the soil on which the 

 plants grew, and the accumulation of overlying 

 strata, which would in course of time produce an 

 amount of pressure sufficient, along with chemical 

 changes, to mineralise the pulpy vegetable matter 

 into a bed of true coal There seems to have been, 

 during the time of the coal-formation, not only a 

 great luxuriance of vegetable growth, fostered by 

 a peculiarly humid and equable climate, but a 

 singularly regular subsidence of the land, accom- 

 panied by pauses of long duration. These con- 

 ditions occurred at no other period of the earth's 

 history, and they were singularly favourable to 

 the production of coal, because, although this 

 mineral does occur in other formations, such as 

 the Oolite, it is always in comparatively small 

 quantity and of inferior value. 



The various ' kinds of coal may be broadly 

 divided into three namely, I. Cannel or Parrot 

 Coal ; 2. Common or Household Coal ; and 3. 



386 



Anthracite. The first includes those coals which 

 are believed to have been formed from decom- 

 posing vegetable matter in water, in a fine state 

 of division, which have little or no lustre, and 

 which, being highly bituminous, yield a large 

 quantity of gas or paraffine oil, according as they 

 are distilled at a high or a low red-heat The 

 second kind includes many sub-varieties, as caking 

 coal, cherry coal, smithy coal, splint coal, all of 

 which are bituminous, but less so than cannel 

 coal. Some of them, however, are regularly used 

 for making gas. Caking coal cakes or fuses to- 

 gether when burning; cherry coal is soft, and 

 breaks into small cubes, and, like most of the 

 varieties of bituminous coal, except cannel, it has 

 a resinous or shining lustre. Splint coal is hard 

 and slaty, and, when of good quality, gives off 

 great heat in burning. The third kind, anthracite, 

 is coal which has had almost all its volatile or 

 bituminous matter driven off by contact with 

 igneous rocks. It is therefore nearly pure carbon, 

 has a high and sometimes iridescent lustre, and 

 is difficult to kindle, but when once ignited gives 

 out intense heat It is chiefly used for smelting 

 ore and for raising steam. 



The coal-measures of Great Britain are supposed 

 to have been originally continuous with those cf 

 France and Belgium, and to have once spread 

 over a much wider area in Britain itself than they 

 now do. Disturbance, denudation, and the depo- 

 sition of newer strata, have combined to limit our 

 accessible coal-fields to those areas which they 

 now occupy. As the productiveness and probable 

 duration of these were not long since made 

 the subject of a searching inquiry by a Royal 

 Commission, we shall best give an idea of the 

 extent of each, by quoting the following table 

 from its first Report, published in 1871 : 



QUANTITIES OF AVAILABLE COAL IN THE CHIEF 

 BRITISH COAL-FIELDS, AT DEPTHS NOT EXCEEDING 

 40OO FEET, AND IN SEAMS NOT LESS THAN ONE FOOT 

 THICK, AS GIVEN IN THE REPORT OF THE COAL 

 COMMISSIONERS, DATED 1871, IN STATUTE TONS. 



South Wales 32,456,208,913 



Midland (Yorkshire, Derbyshire, and 



Nottinghamshire) 18,172,071,433 



Northumberland and Durham 10,036,660,236 



Lancashire and Cheshire 5,546,000,000 



Bristol 4,218,970,762 



North Staffordshire 3,825,488,105 



South Staffordshire, Coalbrookdale, 



and Forest of Wyre 1,906,119,768 



North Wales 2,005,000,000 



Smaller English coal-fields 2,041,620,251 



Total of Scottish coal-fields 97843,465,930 



Total of Irish coal-fields 155,680,000 



Grand total, tons, 90,207,285,398 



The Scottish coal-fields lie in an irregular belt, 

 stretching across the country in a north-east 

 direction, from the coast of Ayrshire to that of 

 Fife, with an average breadth of twenty-five miles. 



In Ireland, as the above table shews, the quan- 

 tity of workable coal is very limited, and consists 

 chiefly of anthracite ; nevertheless, at one period 

 of the earth's history, not less than two-thirds of 

 the country must have been covered by coal-beds, 

 which have been subsequently swept away by 

 denudation. 



Some of the coal included in the foregoing table 

 exists under the Permian rocks, a formation which 

 immediately overlies the coal-measures ; but there 



