The universal geography : earth and its inhabitants

8 THE BEITISH 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 historj' mentioned the names of the tribes who inhabited the British
Islands, the mineral wealth of the Cassitcrides, 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 JN^evis, 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 Sco.tland. This plain, stretching from the Clyde to the Forth, and
/ Pliocene Norwich Crag, Eed Crag. Coralline Crag.
Teiitiary Miocene
I
OK Calnozoic. I Eocene
Bovey Tracer and Miill beds, -with igneous rocks.
Hempstead, Bembridge, Osborne, and Headon beds ;
f Cretaceous ... . .
Bracklesham and Bagsbot beds ; London Clay.
Cbalk, Greensand, Gait, Atherfield Clay.
Wealden Series . . . Weald Clay, Hastings Sands, Purbeck beds.
I
Secondaiiy
' *-'°''^*^'^ Series Portland Oolite and Kimmeridge Clay ; Coral Eag and
OR Mesozoic 1
O.xford Clay ; Combrash, Forest Marble, Bath Oolite
Stoncsfield Slate and inferior Oolite.
I
Lias Clay, Marlstone. Ehretic beds.
Primary
OR PAL.ai0ZOIC
LTriassic New Red Marl (Keuper), New Red Sandstone (Bunter').
Permian .... Magnesian Limestone.
Carboniferous Coal Measures and Millstone Grit ; Carboniferous Lime-
stone and Shales.
Old Red Sandstone and
Devonian . . . . Sandstones, Slate, Limestones, Shales, Marls, and Con-
glomerate.
Silm-ian ... ... Arcnig Slates, Bala or Caradoc beds, Ludlow Rocks.
Cambrian Grits and Slates of Longmynd and Wales, Tremadoc Slates.
Laurentian . ... Gneiss.
;