BLACK DIAMONDS. 343 



whose influence is very potent, as its power of absorbing and retaining 

 heat is thousands of times greater than that of air. Hence, as the ocean 

 was so largely preponderant, there was an atmosphere heavily charged 

 with moisture, which in time was favorable to a warm and equable cli- 

 mate. In fact, the want of annual rings in carboniferous plants proves 

 that there was no winter, and, as the same coal-plants grew at the same 

 time in Europe and America, the same climate must have prevailed. 

 The air was also charged with carbonic acid, for there are no fossils 

 (which Prof. Huxley so beautifully says are the labels that an Almighty 

 hand has put upon the specimens in Nature's museum) in this or any 

 other earlier formation of warm-blooded animals. 



In all these circumstances, therefore, there exist the most advan- 

 tageous conditions for the rapid and continuous growth of vegetation, 

 and, judging from the fossils thereof, it must have gone on with a 

 density and luxuriance that wellnigh surpasses conception. Floating 

 vegetables first made their appearance, spreading their branches and 

 leaves on the surface of the water, and filling the basin or lagoon with 

 their debris^ thus forming a support for the more aerial vegetation, 

 compared with which anything in our day of the same species, in re- 

 spect to size and quantity, fades into insignificance. 



The exuberant growth of the tropics is astonishing to us ; but it is 

 as nothing when we contemplate that of the coal era. For example : 

 JEquisetum, the horse-tail flag, with us is never more than half an inch 

 in diameter, while in the coal-rocks gigantic reeds of this kind were as 

 much as fourteen inches in diameter. Living club-mosses, even in our 

 tropics, attain no great height, but there they were as thick as a man's 

 body and sixty and seventy feet high. Our ferns are of insignificant 

 size, but in those olden days they raised their feathery foliage to a 

 height of sixty feet and upward. There are others that grew to the 

 same wonderful proportions ; and as they fell others sprang up, and 

 thus the " heaping " process continued until Nature caused some sub- 

 sidence of the ground ; the water closed over it all, and the currents 

 deposited mud and sand upon it : if the former, a stratum of slate was 

 the ultimate result ; if the latter, a stratum of sandstone. When this 

 subsidence ceased, fresh growths sprang up and a new deposit was 

 formed, to sink and be covered in its turn ; and as often as these 

 periods of rest and submergence were repeated, so often did a new coal- 

 bed come into existence, and in this is a simple rational explanation 

 why the coal-measures have more than one seam in them. 



If, on the other hand, an elevation took place, the roots of the 

 plants were deprived of their moisture, and they not only ceased grow- 

 ing and the deposit accumulating, but the rains and surface-drainage 

 graduallj' eroded the latter away, and, as it floated ofi*, it became mixed 

 with any earthy matter which the waters may have had in mechanical 

 suspension ; and, when it was finally deposited in some lagoon or over- 

 spread other formations, it ultimately made an inferior coal, or a black 



