440 SPECIAL GEOLOGY. 



allowing the gaseous elements to escape, would be inadequate 

 to produce the desired results, and that coal never could be 

 formed by such a process. The very close analogy presented 

 by peat to lignite and coal affords a striking corroboration of 

 the justice of such a view. 



7. The multiplied instances of trees found erect estab- 

 lish the fact of the coal plants having chiefly grown on 

 the spot where they are now entombed. Not only has 

 Mr. Hawkshaw discovered the group of trees already de- 

 scribed, on the line of the Bolton and Manchester Railway, 

 but Mr. Conway, on forming the railway tunnel at Claycross, 

 five miles south of Chesterfield, found a number of fossil 

 trees, apparently SwiUaria, no fewer than forty in number, 

 standing not less than three or four feet apart, and forming 

 a perfect fossil forest. When we reflect on the accidental 

 nature of these discoveries, it is impossible to resist the 

 conviction that the earth may contain innumerable forests 

 entombed on the spots where they gr ew > many of which the 

 progress of discovery will bring to light. 



The idea of submergence is not new. Opinions which go 

 to the support of this theory have been long expressed by 

 Count Sternberg, Adolphe Brongniart, Lindley and Hutton, 

 Hawkshaw and Bowman. 



Mr. Logan,* in a highly interesting communication on the 

 coal strata of South Wales, states that there is no instance 

 in that district of any seam of coal without a bed of under- 

 clay abounding in Stigmaria ficoides, a marshy plant 

 which existed in such abundance as to have formed, as 

 he conjectures, the chief source of our fossil fuel. In a 

 second communication, on the coal-fields of Pennsylvania, he 

 states that the same phenomenon of the underclay prevails 

 throughout those deposits. 



So much light has been thrown on the formation of coal 

 by these and similar observations, that an opinion now pre- 

 vails that the vegetation which produced the coal grew in 

 broad and shallow lagoons or sheets of water, receiving at 

 intervals deposits of silt and mud, the detritus of neighbour- 

 ing land. These streams were speedily filled up by the 

 growth of a profusion of Stigmaria, until, by the accumula- 



* See Proceedings of Geological Society, vol. iii., No. 69, p. 275. 



