HOW THE COAL BEDS 



from North Wales to Norfolk, was sunk beneath the sea. 

 The lakes disappeared, and above their deposits, as above 

 the rest of England and nearly all Europe except Scandi- 

 navia and patches of Spain, Italy, and the Balkans, a 

 deep ocean rolled, and for many thousands of years 

 deposited a grey ooze of limestone. This limestone is 

 called the Carboniferous or Mountain Limestone. But as 

 time went on this old sea floor began to be slowly raised, 

 and in the shallower waters a great quantity of coarse 

 sand and stones and conglomerate the Millstone Grit, 

 as it is called was deposited. Limestone denotes clear 

 seas ; but the borders of clear seas are often the 

 sites of accumulation of land rocks, and the clear waters 

 of the early Carboniferous sea which stretched from 

 Ireland to the north of Europe were bordered by 

 shores along which mud and shale, gravel and sand were 

 deposited. 



The end of this period was marked in Europe by great 

 disturbances of the earth's crust though perhaps these 

 disturbances, as we have shown in a previous chapter, 

 were not sudden or violent, but were slow upheavals, 

 lasting hundreds of thousands of years. It was at this 

 time that a great system of mountains, sometimes referred 

 to as the Palaeozoic Alps, began to rise. This system of 

 mountains crossed the central part of Europe from the 

 Western Islands to the Sudetes Mountains in the east. 

 Their remnants are seen in the Vosges Mountains, the 

 Hartz Mountains, and the Black Forest at the present 

 time ; and the development of the Ural Mountains was 

 contemporaneous with them. During this time a mild 



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