Prof. T. Rupert Jones — Address. 563 



As a scheme for the general classification of coals the following table may be 

 useful : — 



Highly Bitu-|p , \ parrot-coal ... '... j much altered 



minous. .. J^'*^ ^"ais ) Tasmauite, Better-bed 



/ Torbanite, cannel-coal, \ Vegetable matter 



) parrot-coal j 



~ ismauite, Better- bed 1 o i 



. coal, etc. ) Spore-coals. 



Common Bitu-) | Caking and coking coal, j Laminfe of charcoal 

 minous ') Household coals . . . cherry coal, splint coal, | (mother-coal) & 

 *"") ' and other coals ) hydrocarbon. 



Semi -bitumi-l Free-burning j 1. Charcoal deposited abundantly at first. 



nous. ...) steam coals ...(2. Hydrocarbon partially lost by change. 



Anthracitic ... | ^g|;g^ c^al'^ ^^^ 1 Hydrocarbon nearly all lost by change. 



Anthracite ... Smokeless coal ... | ^^' *^® hydrocarbon lost by heat under pres- 



\ sm-e. 



Coke I^" ^j-tjignjai / Hydrocarbon lost by heat without pressure. 



8. Constituents of the Coal-measures and of Coal. — Sandstone, shale, coal and 

 clay, in successive repetition, constitute (as we all know) the main materials of the 

 'Coal-measures' ('measures' being an old mining term for strata). Each of these 

 substances well deserves the close investigation they have received from numerous 

 observers. We need not take the sandstone in hand now ; it will be enough to 

 say that the quartz -grains have been derived from the quartz of the same granite 

 rocks which gave the little mica-flakes to mix with much of the sandstone, and the 

 kaolin to form the basis of the shales and clays in the same great Carboniferous 

 formation. 



Shales and Ironstone. — The shales are varied ; some are almost purely argillaceous ; 

 others contain carbonaceous matter in different proportions, even becoming quite 

 black and bituminous. The lighter-coloured shales often have plant-remains, 

 especially ferns, scattered through them, and even whole stems and branches of 

 LepidodendroH and Sigillaria, squeezed flat,> and reaching long distances. The 

 darker shales also have plant-remains, but less perfect, and very often shells and 

 other fossils, including relics of fish and numbers of small bivalved crustaceans ; 

 Avith regard to the last, the fishes, when alive, fed on the Cypridae and other 

 organisms, and in turn these little Ostracoda ate the dead fishes when they could. 



Here and there are more or less continuous layers of ironstone, or more frequently 

 groups of nodules parallel with the planes of bedding, and containing either parts 

 of plants, more rarely small limuloids or other crustaceans, or even spiders, scor- 

 pions, insects, or relics of' fishes and amphibia. In some cases the shales are of 

 marine origin, judging from the character of the shells imbedded in them ; but 

 usually the evidence from the fossils is of a negative character. The shells that 

 were formerly thought to be mussel-shells, like freshwater Unios, are now known 

 to belong to a difl:erent family ; and, not being quite the same as any known sea- 

 shell, they may have been estuarine. 



The nodular and the flat masses of clay-ironstones in the shales have been due 

 to the formation of carbonic acid in the water and mud by the decomposition of 

 vegetable matter and the removal of some oxygen from the peroxide of iron present 

 there, and by the carbonic acid thereupon forming carbonate of iron. This then 

 segregated around some organic object in the mud, and, mingled with clay, gave rise 

 to nodules or larger masses of argillaceous ironstone.' In consolidating the nodules 

 frequently split internally, and the fissures of retreat, filled with calcite, blende, 

 pyrites, or other mineral, constitute septa, or divisions, in the septarimn or septarian 

 nodide. The so-called 'beetle-stones ' are septarian nodules broken across, showing 

 central and diverging lines. 



The iron-ores of South Wales are fully treated of in the ' Memoirs Geol. Survey,' 

 Iron-Ores, part iii. 1861, by E. Rodgers, and their fossils by J. W. Salter. From 

 ofiicial sources we learn that the details of Production of Ironstone, chiefly Argilla- 

 ceous Carbonate, from mines under the Coal-mines Eegulation Act, for the year 

 1%!^9 were — 



^ De la Beche, " Memoirs Geol. Survey," vol. i. pp. 185, 186. 



