452 



THE BRITISH ISLES. 



state and its widespread commerce, wliicli Lave in turn proved powerful agents in 

 securing her political ascendancy. How many centuries, nay, how many decades 

 longer will this coal hold out ? This is a pregnant question, the solution of which 



Fig '223.— DiSTiaia-TioN of Coal ix Gkeat Biutain. 

 AooorJing' to null. 



"^■^^g, 



l,00<j feet of 

 the siirfiice. 



Coal .it a 



depth of 1,000 



to 2,000 feet. 



Coal at a depth 

 of from 2,000 

 to 4,000 feet. 



will affect, in a large measure, the destinies not only of the British nation, but of 

 the whole world. 



Geologists have ascertained that the carboniferous strata originally covered a 

 vast portion of the British Islands as with a sheet, but that the destructive and 



