14:6 THE GEOLOGICAL HISTORY OF PLANTS. 



We need not go far in search of the uses of the coal 

 vegetation, when we consider the fact that the greatest 

 civilised nations are dependent on it for their fuel. With- 

 out the coal of the Carboniferous period and the iron-ore 

 which is one of the secondary consequences of coal ac- 

 cumulation, just as bog-ores of iron occur in the subsoils 

 of modern peats, it would have been impossible either to 

 sustain great nations in comfort in the colder climates of 

 the northern hemisphere or to carry on our arts and 

 manufactures. The coal-formation yields to Great Brit- 

 ian alone about one hundred and sixty million tons of 

 coal annually, and the miners of the United States ex- 

 tract mainly from the same formation nearly a hundred 

 million tons, while the British colonies and dependen- 

 cies produce about five million tons ; and it is a re- 

 markable fact that it is to the English race that the 

 greatest supply of this buried power and heat and light 

 has been given. 



The great forests of the coal period, while purifying 

 the atmosphere of its excess of unwholesome carbonic 

 acid, were storing up the light and heat of Palaeozoic 

 summers in a form in which they could be recovered in our 

 human age, so that, independently of their uses to the 

 animals which were their contemporaries, they are indis- 

 pensable to the existence of civilised man. 



Nor can we hope soon to be able to dispense with the 

 services of this accumulated store of fuel. The forests 

 of to-day are altogether insufficient for the supply of our 

 wants, and though we are beginning to apply water-power 

 to the production of electricity, and though some promis- 

 ing plans have been devised for the utilisation of the 

 direct heat and light of the sun, we are stiH quite as de- 

 pendent as any of our predecessors on what has been done 

 for us in the Palaeozoic age. 



In the previous pages I have said little respecting the 

 physical geography of the Carboniferous age ; but, as may 



