98 TOWN GEOLOGY. [IT. 



as the sands and muds which buried them had been. 

 And it was known that at the mouths of certain rivers 

 the Mississippi, for instance vast rafts of dead 

 floating trees accumulated ; and that the bottoms of 

 the rivers were often full of snags, etc. ; trees which 

 had grounded, and stuck in the mud ; and why should 

 not the coal have been formed in the same way ? 



Because and this was a serious objection then 

 surely the coal would be impure mixed up with mud 

 and sand, till it was not worth burning. Instead of 

 which, the coal is usually pure vegetable, parted 

 sharply from the sandstone which lies on it. The 

 only other explanation was, that the coal vegetation 

 had grown in the very places where it was found. 

 But that seemed too strange to be true, till that great 

 geologist, Sir W. Logan who has since done such 

 good work in Canada showed that every bed of coal 

 had a bed of clay under it, and that that clay always 

 contained fossils called Stigmaria. Then it came out 

 that the Stigmaria in the under clay had long filaments 

 attached to them, while when found in the sandstones 

 or shales, they had lost their filaments, and seemed 

 more or less rolled in fact, that the natural place of 

 the Stigmaria was in the under clay. Then Mr. 

 Binney discovered a tree a Sigillaria, standing 

 upright in the coal-measures with its roots attached. 

 Those roots penetrated into the under clay of the coal; 

 and those roots were Stigmarias. That seems to 

 have settled the question. The Sigillarias, at least, 

 had grown where they were found, and the clay 

 beneath the coal-beds was the original soil on which 

 they had grown. Just so, if you will look at any 

 peat bog you will find it bottomed by clay, which clay 



