116 THE STORY OP THE EARTH AND MAN. 



the former is in this period by far the most important 

 we may begin with it. Before doing so, however, to 

 prevent misapprehension, it is necessary to remind the 

 reader that the Flora of the Middle Coal Period is but 

 one of a succession of related floras that reach from 

 the Upper Silurian to the Permian. The meagre flora 

 of club-mosses and their allies in the Upper Silurian 

 and Lower Devonian was succeeded by a compara- 

 tively rich and varied assemblage of plants in the 

 Middle Devonian. The Upper Devonian was a period 

 of decadence, and in the Lower Carboniferous we have 

 another feeble beginning, presenting features some- 

 what different from those of the Upper Devonian. 

 This was the time of the Culm of Germany, the 

 Tweedian formation of the North of England and 

 South of Scotland, and the Lower Coal formation of 

 Nova Scotia. It was a period eminently rich in Lepi- 

 dodendra. It was followed by the magnificent flora 

 of the Middle Coal formation, and then there was a 

 time of decadence in the Upper Coal formation and 

 only a slight revival in the Permian. 



In the present condition of our civilization, coal is 

 the most important product which the bowels of the 

 earth afford to man. And though there are pro- 

 ductive beds of coal in most of the later geological 

 formations, down to the peats of the modern period, 

 which are only unconsolidated coals, yet the coal of 

 the Carboniferous age is the earliest valuable coal 

 in point of time, and by far the most important in 

 point of quantity. Mineral coal may be defined to 



