216 Sir C. Lyell on Fossil Reptilian Remains 



had been suspected some years before on botanical grounds by 

 M. Adolphe Brongniart ; but as the fact was still doubted by 

 some geologists both in Europe and America, it was thought 

 desirable to dig out of the cliffs, and expose to view, several 

 large trunks with their roots attached. These were ob- 

 served to bifurcate several times, and to send out rootlets in 

 all directions into the clays of ancient soils in which they had 

 grown. Such soils or underclays with Stigmaria afford more 

 conclusive evidence of ancient terrestrial surfaces than even 

 erect trees, as the latter might be conceived to have been 

 drifted and fixed like snags in a river's bed. In the strata 

 1400 feet thick above mentioned, root-bearing soils were ob- 

 served at sixty-eight different levels ; and, like the seams of 

 coal which usually cover them, they are at present the most 

 destructible masses in the whole cliff, the sandstones and la- 

 minated shales being harder, and more capable of resisting the 

 action of the waves and the weather. Originally the reverse 

 was doubtless true, for in the existing delta of the Mississippi 

 the clays, in which innumerable roots of swamp trees, such as 

 the deciduous cypress, ramify in all directions, are seen to with- 

 stand far more effectually the excavating power of the river 

 or of the sea at the base of the delta, than do beds of loose 

 sand or layers of mud not supporting trees. 



This fact may explain why seams of coal have so often 

 escaped denudation, and have remained continuous over wide 

 areas, since the roots, now turned to coal, which once tra- 

 versed them, would enable them to resist a current of water, 

 whilst other members of the coal formation, when in their 

 original and unconsolidated state, consisting of sand and mud, 

 would be readily removed. 



The upright trees usually inclose in their interior pillars 

 of sandstone or shale, or both these substances alternating, 

 and these do not correspond in the thickness of their layers, 

 or in their organic remains, with the external strata, or 

 those enveloping the trunks. It is clear, therefore, that the 

 trees were reduced while yet standing to hollow cylinders of 

 mere bark (now changed into coal), in which the leaves of 

 ferns and other plants, with fragments of stems and roots, 

 were drifted together with mud and sand during river inun- 

 dations. The stony contents of one of these trees, nine feet 



