COAL: ITS STRUCTURE AND FORMATION. 435 



Grand' Eury 1 describes several instances of the same kind, 

 and, like Beete Jukes, draws attention to the fact that the 

 coal was laid down in horizontal beds, none being de- 

 posited on the crests of the sandstone ridges until the whole 

 floor had been raised to that level. This method of deposi- 

 tion points to the existence of currents rather than a quiet 

 sheet of water in which the sediment would slowly sink to 

 the bottom, and fill up all irregularities of surface contour. 

 The existence of the numerous thin laminae in coal is 

 another fact which influenced Jukes in his choice of the 

 drift theory of coal formation. Attention has recently been 

 directed to this laminar structure by another advocate of the 

 allochthonous origin of coal seams. 2 



Grand' Eury's exhaustive memoirs on the foundation of 

 coal supply us with a considerable amount of evidence col- 

 lected by one intimately acquainted with the geology and 

 botany of the upper carboniferous rocks ; and the facts 

 which he brings forward clearly point to the subaqueous de- 

 position of layers of carbonaceous sediment. He does not 

 favour the view that the vegetable ddbris was drifted for a 

 long distance from forest-covered land, but considers the 

 facts more readily explained on the assumption of a com- 

 paratively short transport. Grand' Eury's views are thus 

 concisely stated by Solms-Laubach : 3 "Coal seams were 

 formed in broad land-locked lake basins (lagoons) surrounded 

 by wooded swamps, in which the decaying vegetation, soften- 

 ing and rotting as it lay on the ground, produced in time a 

 layer of matter of vast thickness. The water of frequent 

 rain-storms running slowly off in trickling streams gradually 

 carried away with it the softened wood in shreds from inside 

 the encasing rind, which was itself ultimately broken up and 

 conveyed with other deposits into the basin. Here the 

 processes which lead to the formation of coal took the place 

 of decay, the mass of the coal being produced from the rind, 

 while the particles of softened wood were converted into 

 fibrous coal. The masses of aquatic and marsh plants, 

 which covered the surface and margins of the basin with 



1 Grand' Eury (2). 2 Gresley. See also Goodchild. 8 P. 23 (1). 



