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together with marine and estuary shells, phsenomena indicative of 

 drift. Admitting that the floors of the coal or underclay present a 

 great uniformity both in the absence of other plants and in the 

 almost general occurrence of the Stigmaria, Mr. Williamson allows 

 that a plant, found so very generally in such a position, may have 

 grown in estuaries into which the other vegetables were drifted. 

 Acknowledging that the drift theory is open to some objections, he 

 stated that one of the greatest of these is, in his opinion, the ex- 

 tent and uniformity of some of the thin seams of coal. On this point, 

 however, I must be permitted to say, that, if admitted, the diflSculty 

 must be applied to numberless other deposits of all ages, which 

 every one knows must have been accumulated under water. Sub^ 

 aqueous action of a tranquil nature is, it appears to me, precisely 

 the agency by which we can satisfactorily explain the uniformity of 

 many thin layers containing vegetables which are extended over 

 wide areas, as in the copper grits of Russia before alluded to. By 

 Avhat other possible means, for example, can we explain the wide 

 extent of the thin copper slate of Germany with its associated fishes 

 on the still thinner bone-bed at the base of the Lias ? So far then 

 from being a phsenomenon which invalidates the formation of coal 

 under water, it seems to me, that the very fact of a thin and equable 

 deposit is an almost impossible condition, if we insist exclusively upon 

 the submergence of forests or jungles in skit, in which considerable 

 .irregularities of outline must in all probability have prevailed. 



On my own part, and that of my fellow-travellers in Russia, I 

 have brought before this Society what we consider strong evidences 

 against the too general adoption of this favourite theory. We have 

 told you that in many instances the Stigmaria ficoides occurs in 

 loose and incoherent sands, as well as in shales, and is frequently 

 present where no coal is seen ; but what we chiefly insist upon is, 

 that all the coal-seams of the South of Russia, without exception, 

 alternate repeatedly Avith beds of purely marine origin. In one sec- 

 tion of the Donetz coal-field it has been stated, that at least twelve 

 beds of marine limestone alternate in one vertical section Avith 

 thirteen seams of coal and numerous bands of sandstone and shale, 

 in which many species of plants, besides Stigmariae, are confusedly 

 heaped together. But we need not go to Russia for such examples. 

 The whole of the mountain limestone or lower coal series of the north 

 of England is charged, though not to so great an extent, with proofs 

 of the alternation of marine deposits with coal and its associated 

 sandstone and shale. 



The coast of Northumberland, to the north of Alnwick, presents 

 evidences of thin seams of coal resting at once on sandstone, and 

 intimately connected with limestone full of sea shells. Advancing 

 northwards to Berwick, and to beyond the Tweed, purely marine 

 strata re-occur, charged with still more carbonaceous matter; and, 

 in the same series on the noi'th-western parts of England, we have 

 frequent examples of the persistence of what must be called ex- 

 clusively marine conditions. Throughout that vast succession of 

 beds, all the animal remains with which geologists have become 



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