V ON THE FORMATION OF COAL 153 



the Sigillaria bear more resemblance to the rhizomes of certain 

 aquatic plants ; yet, structurally, they are absolutely identical 

 with the roots of Cycads, which the stems also resemble. 

 Further, the Sigillaricc grew on the same soils which supported 

 Conifers, Lepidodendra, Cordaites, and Ferns plants which 

 could not have grown in water. Again, with the exception 

 perhaps of some Pinnularice and Asterophyllttes, there is a 

 remarkable absence from the coal measures of any form of 

 properly aquatic vegetation. (7) The occurrence of marine, or 

 brackish-water animals, in the roofs of coal-beds, or even in the 

 coal itself, affords no evidence of subaqueous accumulation, 

 since the same thing occurs in the case of modern submarine 

 forests. For these and other reasons, some of which are more 

 fully stated in the papers already referred to, while I admit that 

 the areas of coal accumulation were frequently submerged, I 

 must maintain that the true coal is a subaerial accumulation by 

 vegetable growth on soils, wet and swampy it is true, but not 

 submerged." 



I am almost disposed to doubt whether it is- 

 necessary to make the concession of " wet and 

 swampy " ; otherwise, there is nothing that I know 

 of to be said against this excellent conspectus of 

 the reasons for believing in the subaerial origin of 

 coal. 



But the coal accumulated upon the area covered 

 by one of the great forests of the carboniferous 

 epoch would, in course of time, have been wasted 

 away by the small, but constant, wear and tear of 

 rain and streams, had the land which supported it 

 remained at the same level, or been gradually 

 raised to a greater elevation. And, no doubt, as 

 much coal as now exists has been destroyed, after 

 its formation, in this way. What are now known 



