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COAL: ITS GEOLOGICAL & ECONOMICAL HISTORY. 



By the Rev. P. B. BRODIE, M.A., F.G.S., Vice-President of 

 the Warwickshire Naturalists' Field Club. 



After stating that the geology of the surrounding district had 

 been so fully and ably described by his friend Mr, Symonds, that 

 it was quite unnecessary for him to enter generally upon the subject, 

 he said he would take advantage of being in the immediate neighbourhood 

 of the interesting coal field in the Forest of Dean to confine his observations 

 to the geological history of coal. Mr. Brodie then gave a brief sketch of 

 the carboniferous series of rocks, which consist of alternations of lime- 

 stone, sandstone, shales, and iron stone, with subordinate bands of 

 coaL Under the coal itself, in most cases, there was a bed of clay, 

 called "fire clay," because it was impervious to heat. Coal was based 

 generally on the mountain limestone, and deposited in limited areas, 

 but the Dudley coal field was an exception, and rested immediately 

 on the Silurian rocks. The Forest of Dean coal field was a very small one. 

 The Shropshire was larger, and the Dudley coal field larger stiU. The South 

 Wales coal field was very extensive, and the Northern the largest of alL 

 In Dean Forest, between the lowest coal seams underlying the millstone 

 grit, are about 800 feet of green sandstones full of the remains of plants, 

 and the regular coal overlies them. Sections may be seen at Dry- 

 brook and on the railway, near Sudley. The deepest coal mines 

 are those of Northumberland and Durham, some of which are 300 

 yards, or 900 feet below the surface. The thickest bed of coal is 

 the main coal in Staffordshire, that of Dudley, which was thirty feet in 

 thickness, but as a general rule the strata of coal are much thinner, not 

 more than from three to five feet. The Derbyshire coal measures yield 

 about thirty different beds of coal, varying from six inches to eleven feet in 

 thickness. The South Wales coal field was about 100 miles long and 25 

 miles broad. The entire thickness of the carboniferous series was about 

 15,000 feet, and if all the various beds of coal itself were placed together 

 they would amount to about 2,000 feet in thickness ; but of course all these 

 beds did not appear togetherin one locality, or if they did were not approach- 

 able. Some geologists think that all these coal fields were at one time 

 connected together ; others that they were separate and independent deposits, 

 partly lacustrine, fluviatile, or marine ; that England was a series of islands 

 formed by sinking coral reefs of mountain limestone, and that coal was 

 deposited over them, and that they were afterwards separated and broken 

 up by volcanic action, causing what are called "faults" in all directions. 

 After the deposition of coal volcanic disturbances were taking place with 



