THE GROWTH OF COAL 243 



attribute in great part to aquatic plants, allied to modern 

 Salvinia, etc., are chiefly found. ^ 



For these and other reasons, some of which are more fully 

 stated in the papers 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 would add the further consideration, already urged elsewhere, 

 that in the case of the fossil forests associated with the coal, the 

 conditions of submergence and silting-up which have pre- 

 served the trees as fossils, must have been precisely those 

 which were fatal to their existence as living plants, a fact 

 sufficiently evident to us in the case of modern submarine 

 forests, but Qften overlooked by the framers of theories of the 

 accumulation of coal. 



It seems strange that the occasional inequalities of the floors 

 of the coal beds, the sand or gravel ridges which traverse them, 

 the channels cut through the coal, the occurrence of patches 

 of sand, and the insertion of wedges of such material splitting 

 the beds, have been regarded by some able geologists as 

 evidences of the aqueous origin of coal. In truth, these 

 appearances are of constant occurrence in modern swamps 

 and marshes, more especially near their margins, or where 

 they are exposed to the efl"ects of ocean storms or river inun- 

 dations. The lamination of the coal has also been adduced 

 as a proof of aqueous deposition ; but the miscroscope shows, 

 as I have elsewhere pointed out, that this is entirely different 

 from aqueous lamination, and depends on the superposition of 

 successive generations of more or less decayed trunks of trees 

 and beds of leaves. The lamination in the truly aqueous can- 

 nels and carbonaceous shales is of a very different character. 



It is scarcely necessary to remark that in the above summary 



^ "Geological History of Plants," Bulletin Chicago Academy of 

 Sciences, 18S6. 



