HOW THE COAL BEDS 



It would hardly seem unreasonable to suppose that 

 these depositions, and the changes that brought them 

 about, might have occupied as much time as the forma- 

 tion of the coal beds. This would double the figures, 

 and make this period last something between two million 

 and five million years. 



In the coal as we know it are the remains of great 

 forest trees ; gigantic tree-ferns for the most part, and of 

 many small plants forming a close thick sod, partially 

 buried in whole countries of marsh land. 



Every one knows those marsh plants, which bear 

 the vulgar name of " mareVtail." These humble plants 

 were represented during the coal period by trees from 

 twenty to thirty feet high and four to six inches in 

 diameter. Their trunks have been preserved to us : they 

 bear the name of Calamites. 



The Lycopods of our age are humble plants, scarcely a 

 yard in height, and most commonly creepers ; but those 

 of the ancient world were trees of eighty or ninety feet in 

 height. Their leaves were sometimes twenty inches long, 

 and their trunks a yard in diameter. Such are the 

 dimensions of some specimens which have been found. 

 Another Lycopod of this period attained dimensions 

 still more colossal. The Sigillarias sometimes exceeded 

 100 feet in height. Herbaceous Ferns were also exceed- 

 ingly abundant and grew beneath the shade of these 

 gigantic trees. It was the combination of these lofty 

 trees with the undergrowth of smaller vegetation which 

 formed the forests of the Carboniferous period. " What 

 could be more surprising," exclaims Figuier, "than the 



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