174 ON THE ORIGIN OF COAL. 



and establish the rival theory, which attributes 

 the formation of Coal seams to vegetable matter, 

 grown upon the identical places where it is now 

 found. 



In most of the Coal seams of Lancashire, some 

 evidence is found of upright stems of trees, for 

 the most part Sigillarise, standing upon the roof 

 of the Coal. Professor Ansted, in Vol. I. p. 

 262, of his Treatise on Geology, in speaking of 

 Sigillaria, says, " The great abundance of the 

 large stems, referred to this genus, is a fact which 

 seems to show that it was one of those to whose 

 presence much of the solid matter of the Coal is 

 due. Many instances are known, in which trunks 

 or stumps of large trees of this kind are found 

 close together, in an erect or highly inclined 

 position ; and this, not only in England, but also 

 in the continental Coal-fields, and more particu- 

 larly in that of St. Etienne, where a remarkable 

 group has been described by M. Brongniart. 

 It must not be supposed, however, that the trees 

 grew upon the spot where they are thus singularly 

 arranged ; it is more probable that they may have 

 been caught, and stopped in their passage down a 

 rapid stream, and, like the snags on some of the 

 great American rivers, have been detained till the 



