8 THE BRITISH ISLES. 



more minute survey has been carried on, revealing not only the surface geology 

 in all its details, but throwing additional light upon the great mineral and 

 metallic wealth hidden in the bowels of the earth. Even in fabulous times, 

 long before history mentioned the names of the tribes who inhabited the British 

 Islands, the mineral wealth of the Cassiterides, or Cornwall, attracted merchants 

 from the Mediterranean ; and to the present day, whatever may be the mineral 

 riches of America or Australia, the British Islands remain the most productive 

 mining country in the world. They owe their pre-eminence, however, not to tin, 

 but to coal and iron. 



The geological structure of Great Britain is prominently exhibited in its 

 surface features. The older palaeozoic rocks, which compose the most rugged 

 and elevated mountain regions, lie to the west and north-west, whilst rocks of more 

 recent age are spread over the hilly districts and lowlands. 



In the rugged Highlands, which to the north of a line drawn from the Firth of 

 Clyde to Stonehaven, on the German Ocean, fill up nearly the whole of Northern 

 Scotland, are found gneiss and mica schist of the Silurian age, with numerous bosses 

 of granite and syenite rising above the general level, and forming some of the 

 most prominent peaks. Along part of the west coast these Silurian rocks overlie 

 gneiss and sandstone of Cambrian and Laurentian age, closely resembling similar 

 formations found in Canada. A deep fissure, occupied by a chain of lakes, and 

 bounded by steep hills, stretches for a hundred miles from Loch Eil to the 

 Moray Firth. This is the Glenmore, or *' large valley." It separates the 

 northern Highlands from the Grampians, in which rises Ben Nevis, the culmi- 

 nating point of the British Isles. The whole of this tract is sterile and deso- 

 late in aspect, consisting largely of peaty moorlands and brown heaths, and 

 intersected by narrow glens and valleys, which afford pasturage to black cattle 

 and sheep. 



A wide plain separates this inhospitable region from the hilly district of 

 Southern Scotland. This plain, stretching from the Clyde to the Forth, and 



I Pliocene Norwich Crag, Red Crag, Coralline Crag. 



Miocene Bovey Tracey and Mull beds, with igneous rocks. 



Eotene Hempstead, Bembridge, Osborne, and Headon beds ; 



Bracklesham and Bagshot beds ; London Clay. 



f Cretaceous Chalk, Greensand, Gait, Atherfield Clay. 



I Wealden Series .... Weald Clay, Hastings Sands, Purbeck beds. 



,, j Oolitic Series Portland Oolite and Kimmeridge Clay ; Coral Rag and 



>r" i Oxford Clav ; Combrash, Fol-est Marble, Bath Oolite : 



OR Mksozoic ! ^ « , , ^, T . r • ,- T 



I Stonesncld Slate and inferior Ooute. 



I Lias Clay, Marlstone, Rhsetic beds. 



iTriassic New Red Marl (Keuper), New Red Sandstone (Bunter). 



f Permian Magnesian Limestone. 



Carboniferous Coal Measures and Millstone Grit ; Carboniferous Lime- 

 stone and Shales. 



Old Red Sandstone and 



i Devonian Sandstones, Slate, Limestones, Shales, Marls, and Con- 

 glomerate. 



Silurian .... Arenig Slates, Bala or Caradoc beds, Ludlow Rocks. 



Cambrian Grits and Slates of Longmynd and Wales, Tremadoc Slates. 



•^Laurentian Gneiss. 



Primary 



OR PaLcEOZOIC 



