4:86 



COAL— FOSSIL FORESTS 



[Ch. XXIV 



withstand far more effectually the undermining 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 remain continuous over wide areas, since the, tough 

 roots, now turned to coaj, which once traversed them, would enable 

 them to resist a current of water, whilst other members of the coal- 

 formation, in their original and unconsolidated state of sand and mud, 

 would be readily removed. 



In regard to the plants, they belonged to the same genera and most 

 of them to the same species, as those met with in the distant coral- 

 fields of Europe. In the sandstone, which filled their interiors, I fre- 

 quently observed fern-leaves, and sometimes fragments of Stigmaria, 

 which had evidently entered together with sediment after the trunk 

 had decayed and become hollow, and while it was still standing under 

 water. Thus the tree, a b, fig. 540, the same which is represented at 

 a, fig. 541, or in the bed e in the larger section, fig. 539, is a hollow 



Fig. 540. 



Fossil tree at right angles to the planes of stratification. 

 Coal-measures, Nova Scotia. 



Fig. 541. 



Erect fossil trees. Coal-measures, Nova Scotia. 



trunk 5 feet 8 inches in length, traversing various strata, and cut off 

 at the top by a layer of clay 2 feet thick, on which rests a seam of 

 coal (b y fig. 541) 1 foot thick. On this coal again stood two large 



