412 Sir Roderick I. MurchisorCs 



interior, as shown by Professor W. King. Seeing that in these 

 cases quietly deposited limestones with marine shells (some of 

 them, indeed, of estuary character) rest upon beds of coal, and 

 that in many other cases purely marine limestones alternate fre- 

 quently with layers of vegetable matter and coal, may we not be 

 led to modify the theory, founded on the sound observation of 

 Sir W. Logan, by* which the formation of coal has been rather 

 too exclusively referred to terrestrial and freshwater conditions? 

 May we not rather revert to that more expansive doctrine, which 

 I have long supported, that different operations of nature have 

 brought about the consolidation and alteration of vegetable matter 

 into coal ? In other words, that in one tract the coal has been 

 formed by the subsidence in situ of vast breadths of former jun- 

 gles and forests; in another, by the transport of vegetable mater- 

 ials into marine estuaries ; in a third case, as in Russia and Scot- 

 land (where purely marine limestones alternate with coal), by a 

 succession of oscillations between jungles and the sea; and lastly, 

 by the extensive growth of large plants in shallow seas ? 



" The geological map of Edinburghshire prepared by Messrs. 

 Howell and Geikie, and recently published, with its lucid explana- 

 tions, affords, indeed, the clearest proofs of the frequent alterna- 

 ations of beds of purely marine limestone charged with Product! 

 and bands of coal, and is in direct analogy with the coal fields of 

 the Donetz, in Southern Russia.* 



" In sinldno; throuo;h the extensive coal tracts around Manches- 

 ter (at Dukinfield), where one of the shafts already exceeds in 

 depth the deepest of the Durham mines, rigorous attention will, I 

 hope, be paid to the discovery of the fossils which characterize 

 each bed passed through, not merely to bring about a correctly 

 matured view of the whole history of these interesting accumula- 

 tions, formed when the surface of our planet was first furnished 

 with abundant vegetation, but also for the practical advantage of 

 the proprietor and miner, who, in certain limited areas, may thus 

 learn where iron-ores and beds of coal are most likely to be per- 

 sistent. In carrying out his survey work through the north-west- 

 ern coal tracts of Lancashire, to which the large or six-inch Ord- 

 nance map has been applied, one of the secretaries of this section, 

 Mr. Hull, has done good service in accurately defining the tracts 



* See " Russia in Europe and the Ural Mountains," Vol. 1. 



