Murchisons Silurian System. 235 



their character is however so completely lost that whole 

 trunks are found crumbling to pieces, which present the frac- 

 ture and other characters of coal. With such phenomena be- 

 fore our eyes, it is no wild hypothesis to suppose that if many 

 parts of the basins of great rivers were elevated and laid dry, 

 we should find along their course a succession of changes 

 from the decaying drift wood down to coal itself. Thus it 

 is, says Mr. Murchison, that throughout the whole series of 

 sedimentary strata wherever impressions of plants occur, there 

 also do we find some traces of the existence of coal com- 

 mencing. In tertiary periods, when the relations of land and 

 water were approaching to their present condition, we have 

 many proofs of similar accumulations. In the deep gorges 

 of the Alps we find carbonaceous matter piled up with alter- 

 nating layers of sandstone and shale, on which are impressed 

 the forms of various plants ; and in some places containing flu- 

 viatile and terrestrial shells. These were evidently heaped up 

 by rivers and lakes ; while other accumulations of a similar na- 

 ture pass under strata charged with marine remains, little 

 differing from those of the present day. This state of things 

 would have been produced in a condition of the globe diver- 

 sified with continents, rivers, and lakes as at present ; and 

 although the plants found in the condition alluded to are 

 chiefly different from those that now exist, yet they belonged 

 to Dicotyledonous classes. Descending from tertiary to 

 newer secondary rocks, all the animals and plants which are 

 found in the strata are dissimilar to those now living, and 

 they are such as to prove frequent alternations from land to 

 sea, a condition of the surface less favourable to the pro- 

 duction of vegetables than animals. From this period we 

 descend into the ancient strata in which the fossil plants 

 are not only different from those of the present day, but also 

 from those of intermediate periods. The vegetation of this 

 distant epoch presents an exclusively tropical character in 

 the most northern latitudes in which coal formations have 



been found. 



2 T 



