TRANSACTIONS OF SECTION C. 627 



like a burst peat-bog of the present day (Buckland), the fluid carbonaceous pulp 

 escaped from its birthplace, and found local hollows at lower levels that could 

 receive and keep it. It is also suggested that such black, decomposed, fluid refuse 

 of a swampy jungle, bordering a lagoon, might drain into the water, and settle as 

 carbonaceous mud, or as coal itself, among the water-plants there. (Grand'Eury.) 

 If poured in suddenly, it probably overwhelmed and poisoned many fishes. 

 * The cannel coals, being wholly subaqueous, have not formed and do not possess 

 mineral charcoal.' (Dawson.) 



Torbanite consists almost entirely of minute sub-globular accretions of hydro- 

 carbon (amber-coloured by transmitted light), derived either from chemical change 

 of plant-remains, or, more probably, directly from lycopodiaceous spores. 



Spore-coal.— Y ery much of the substance of some coal-beds consists of lycopo- 

 diaceous spores that have been traced to the great lycopods, Lepidode^idron and 

 Sigillaiia, allied to the club-mosses and Selaginellce, and were probably shed 

 periodically in enormous quantities. (Prestwich and Morris, Hooker, Binney, 

 Williamson, Carruthers, Balfour, Huxley, E. T. Newton, Orton, Dawson, Rheinsch, 

 Wethered, Bennie, Kidston, and others.) Mr. E. Wethered has suggested that the 

 chief material in common coal was derived from the spores of a water-plant nearly 

 allied to Isoetes, and that woody material has supplied but little of the hydro- 

 carbon. He objects to the theory of 'submerged forests ' because of the difficulty 

 that Professor Dana has described, resulting in the calculation that for a four-foot 

 seam of coal there would be required a thickness of 32 feet of accumulated forest 

 vegetation and 48 feet for four feet of anthracite.* The macrospores of Isoetes 

 lacustris have been found in the mud dredged in Loch Coulter, Stirlingshire, bv 

 Mr. Thos. Scott.2 



' Dawson is disposed to think that the tuberin of cork, of epidermis in general, 

 and of spore-cases in particular, is a substance so rich in carbon that it is very 

 near to coal, and so indestructible and impermeable to water that it has contributed 

 more largely than anything else to the mineral.' ^ Prestwich refers to these, and 

 especially to gums and resins, as main constituents of the coal ; and argues that 

 the climate was warm and moist, with a larger percentage of carbonic acid than 

 exists at the present day, and a more rapid plant-growth.* 



Messrs. Bennie and Kidston* have not only carefully given the botanical 

 history of Lepidodendron and Sigillaria, and of their fructification, but have 

 described the spores met with in their examination of the Scotch Carboniferous 

 strata, and have given their conclusions as to the nature and condition of the 

 beds from which the spores were collected. The splint and parrot coals yielded 

 most ; the cherry or soft coals are too far bituminised to show them clearly, 

 though present. Some fireclays yield them in the upper two or three inches. 

 Some thin shales (plant-beds and fakes) yield spores, and some have plant-remains 

 as well. 'Carbonised wood was common in all the poor or shale-like coals. . . . 

 Some of the thin coals were almost entirely composed of such carbonised vegetable 

 matter.' Fragments of scorpions and eurypterids occur plentifully in some of 

 the ' old soils ' (fireclays). The former, being land-animals, and probably adapted 

 to a hot (or, at least, warm) climate, are among the most interesting of the coal- 

 fossils. 



Drift-coal. — Formerly, more so than now, it was thought by some that the coal 

 had been formed by the accumulation of drifted timber and floating masses of 

 vegetation in rivers and estuaries. There are several difficulties in the way of 

 this hypothesis. There would have been more ash in the coal, because the water 

 would shift and deposit sand and clay, together with rafts and grass islands ; and 

 the ash of pure coal agrees in relative quantity and composition with the earthy 

 matter naturally contained in plants. (Green and others.) How far a calculation 

 could be made as to a given quantity of ash in coal, and the amount of mineral 



" Journ. Boy. Microsc. Soc, ser. 2, vol. v., 1885, pp. 406-420. 



* Report of the Fishery Board, 1890. 



• Balfour, Palfrotitological Botany, 1872, p. 67. 



♦ Geology, vol. ii., 1888, pp. 117-120. 



' Proceed. Boyal Phyg. Soc., Edinburgh, vol. ix. 1886, pp. 82-117. 



s s 2 



