Theory of the Origin of Coal. 119 



5000 feet contain the plant Stigmaria fic aides usually with its 

 leaves attached, — that both the roofs and floors indicate a 

 very tranquil method of accumulation, — that the coal is free 

 from admixture of foreign or drifted materials, and that large 

 trees frequently stand upright, this author is induced to be- 

 lieve that the vegetables out of which the coal has been formed, 

 grew upon the spot. 



At the same meeting, this view was contested by Mr W. C 

 Williamson, also well acquainted with the structure of the 

 country aroimd Manchester. His chief arguments were, 

 however, derived from other tracts, and they assisted in 

 proving,— 15^, The frequent association of marine shells with 

 coal (as at Coalbrook Dale, and in Yorkshire). 2dly, The 

 very triturated and broken condition of the plants, as well as 

 their great intermixture in the sandstone and grits, coupled 

 with the fact that large quantities of vegetables are often 

 matted together with marine and estuary shells, phenomena 

 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 extent and 

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

 however, 1 must be permitted to say, that, if admitted, the 

 difficulty must be applied to numberless other deposits of all 

 ages, which every one knows must have been accumulated 

 under water. Subaqueous action of a tranquil nature is, it 

 appears to me, precisely the agency by which we can satis- 

 factorily explain the uniformity of many thin layers contain- 

 ing vegetables which are extended over wide areas, as in the 

 copper grits of Russia before alluded to. By what 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 tliinner bone-bed at the base of the Lias ? So far 

 then from being a phenomenon which invalidates the forma- 

 tion of coal under water, it seems to me, that the very fact of 

 a thin and equable deposit is an almost impossible condition. 



