104 CRITIQUES AND ADDRESSES. [v. 



action. (6) Though the roots of 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 SigiUarice 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 Asterophyllites, 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 sub- 

 aqueous 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 ; " other- 

 wise, 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 

 as coal districts owe their importance to the fact that 

 they were areas of slow depression, during a greater or 

 less portion of the carboniferous epoch ; and that, in 

 virtue of this circumstance, Mother Earth was enabled 

 to cover up her vegetable treasures, and preserve them 

 from destruction. 



Wherever a coal-field now exists, there must formerly 

 have been free access for a great river, or for a shallow 



