694 



HISTORICAL GEOLOGY. 



coal-field of Northumberland and Durham, about Newcastle, 796 square 

 miles. 



In Scotland, the beds cover an area 100 miles long by 25 broad, lying in 

 the depression between the Grampian range on the north and the Lammer- 



n2fi. 



Tig. 1126, Geological map of England. The areas lined horizonteUy and numbered 1 are Silurio-Cambrian ; those 

 lined vertically (2) Devonian ; those cross-lined (3) Subcarboniferous ; the black areas (4) Carboniferous ; the 

 dotted areas (5) Permian ; those lined obliquely from right to left (6) Triassic, (7 a) Lias, (7 b) Oolyte, 

 (8) Wealden, (9) Cretaceous ; those lined obliquely from left to right (10, 11) Tertiary. A is London ; 

 B, Liverpool ; C, Manchester ; D, Newcastle. Eamsay. 



muirs on the south. The most of the workable coal-beds occur in the Sub- 

 carboniferous. 



In Ireland, over its center and to the southwest, a large part of the 

 surface rock is Subcarboniferous limestone. It is believed that the Coal- 

 measures once covered this limestone. 



