ON THE ORIGIN OF COAL. 173 



all the Coal seams. The various arenaceous and 

 argillaceous deposits of the Coal measures were 

 thus accounted for, but no sufficient reason was 

 assigned for the Coal seams themselves contain- 

 ing so little of transported matter. 



As before stated, the seams of Coal are gene- 

 rally found lying upon a fine deposit of hardened 

 clay or silt, indicating great quietude in its 

 formation, and scarcely any trace of a current. 

 In fact, we have in the floor a fine rich soil, well 

 calculated to have produced a luxuriant crop of 

 vegetation, full of immense numbers of Stigmaria 

 ficoides, now proved by the trees of St. Helens 

 and Dukinfield, to be nothing more than the 

 roots of Sigillaria.* So their presence under 

 the seams of Coal, is now fully accounted for, 

 being merely the roots in situ of the forests of 

 Sigillaria, that have chiefly formed the beds of 

 Coal found lying above them. These fossils are 

 of great value in accounting for the true formation 

 of Coal seams, and must for ever do away with 

 the drift hypothesis, so far as concerns those 

 seams in which they are found in the floors, 



*Phil. Mag. for March, 1844, and October, 1845; also. 

 Quarterly Journal of the Geological Society, for Nov. 1840. 



