•68 ABSTRACTS OF LECTURES. 



Of these, that held by Lyall, Dawson, Delabeche, and other 

 geologists, was that the coal-beds are the product of the 

 decay of the vegetation of the period on the spot where it 

 lived and grew, whether on dry land, or on marshy or sub- 

 merged ground as is more probable. 



Grand' Eury modified this theory by supposing that a 

 great deal of coal was deposited not where its materials grew, 

 but in water of various depths near at hand ; as one might 

 conceive of the trees from the edges of a great fresh or 

 •brackish water lake to fall into that lake and becoming water- 

 logged, sink, and cover the bottom. 



The most recent theory, the delta theory of Fayol, last 

 received attention. This assumes that the trees and plants 

 composing the coal grew in forests by the sides of streams, 

 which in time of flood bore them down in their waters to lakes 

 or to the sea, where they were deposited as they became 

 waterlogged, and covered up later on by the mud and sand 

 of the advancing delta. Fayol set up this theory on the 

 evidence of the occurrence of coal in the basin of Commentry 

 in central France; and the facts as established in this and 

 other cases warrant his deductions, but the universality of 

 this delta formation as advocated by its author cannot be 

 conceded in the face of the manner of occurrence of coal in 

 the coalfields of Newcastle and elsewhere. 



In the second portion of the lecture were discussed the 

 methods by which wood is transformed into coal. The 

 suggestion of the filling up of the pores of wood with bitumen 

 injected into them was shown to be untenable. The purely 

 physical theory that heat, pressure and chemical action are, 

 with sufficient time limit, in themselves capable of producing 

 the observed changes, was by the instances in which greatly 

 altered products are sometimes found in younger rocks than 

 others less altered shown to be not always applicable. 

 Renault's theory of "The Bacterial Origin of Coal" was then 

 explained. As at the present time bacteria and fungi are the 

 pauses of the decomposition and decay of wood, so in coal- 



