GREAT BRITAIN 



373 



surface and original inclination of which arcapproxi 

 ninthly in.liiMie.l by the -nmmit- of the various, 

 mountain-masses ami ili- direction of the principal 

 n\.is The Highlands are intersected from south- 

 'OIK >nli cast bv the Great Glen, which probably 

 occupies tin- line oc a dislocation. It inenstomaty 

 in geographical text lionks to Hiteak of the ' range 

 of tin- (Jniinpiaiis,' hut tin- Highland mountains do 

 n.. I trend in linear directions, hut rather form con- 

 hi-.nl groups. It is i>rohahly owing to the fact that 

 many of the rivers and streams run in certain more 

 or le* definite directions that the mountains have 

 been described as linear ranges. The greatest height 

 reached is 4406 feet in Ben Nevis, which is the 

 culminating point of the Highlands (q. v. ), less 

 eminences being Hen Macdhui ( 4296 feet ) and Ben 

 Lawers (3984; with cairn, 4004). The southern 

 limit of the Highlands is defined by a line drawn 

 from the Kirth of Clyde at Helensburgh north-east 

 to the sea-coast at Stonehaven. North of this line 

 there are of course considerable tracts of less 

 elevated ground, especially along the coast in Aber- 

 ileeushire and the borders of the Moray Firth. Caith- 

 ness is another comparatively low-lying and gently 

 undulating plain. The coast-line of the Highlands, 

 particularly in the west, is repeatedly broken by 

 numerous and large fiords or sea-lochs, in which the 

 sea is usually abnormally deep. And opposite the 

 same coasts appear the numerous islands of the Inner 

 and Outer Hebrides. These fiords are simply sub- 

 merged land-valleys, while the islands referred 

 to are the higher parts of the depressed continental 

 plateau. There is reason to betjeve that at a very 

 late geological date the Scottish coasts extended out- 

 wards to what is now the contour line of 100 fathoms. 

 One of the most marked features of the Highlands 

 is the multitude of fresh-water lakes. These vary 

 in size from mere tarns to large mountain-valley 

 lakes like Lochs Lomond, Ness, Awe, Shin, Maree, 

 Tay, &c., and most of them occupy rock-basins, 

 which are comparable in character to the deep 

 hollows that occur in the sea-lochs. 



The Central Plain of Scotland may be described 

 as a broad depression of relatively easily eroded 

 materials lying between two tablelands of less 

 readily denuded rocks. The principal features of 

 this low-lving tract have a north-east and south- 

 west trend determined by geological structure, as is 

 seen in the Sidlaw Hills, the Ochil Hills, the Len- 

 nox Hills, &c., in the north, and in the Pentland 

 Hills in the south. The surface of the lowland 

 tracts is likewise diversified by many more or less 

 abrupt and isolated hills, such as Arthur's Seat, 

 Dalmahoy Crags, the ' Castle-rocks ' of Edinburgh 

 and Stirling, &c. Most of these heights consist of 

 igneous rocks of a more durable character than the 

 strata of sandstone, shale, &c., which surround 

 them. 



The Southern Uplands of Scotland form a broad 

 belt of high ground extending from the sea-coast 

 of Haddingtonshire and Berwickshire south-west to 

 the shores of Ayrshire and Galloway. Like the 

 Highlands the area of the southern uplands is simply 

 an old tableland, furrowed into narrow ravine and 

 wide dale by the operation of the various agents of 

 erosion. The general configuration of this upland 

 tract is somewhat tame and monotonous. The 

 mountains are flat-topped elevations with broad 

 rounded shoulders and smooth grassy slopes. They 

 do not run in linear directions but form irregular 

 groups and masses. The rocks that enter into their 

 composition are chiefly Silurian, greywackes, and 

 shales, and consequently there is less variet\ i 

 contour and colour than in the Highlands. The 

 hills are not only Hatter atop but are generally 

 much smoother in outline, there being a general 

 absence of those beetling crags and precipices which 

 are so common in the Highlands. Now and again, 



however, tin- mountains assume a rougher aspect, 

 more especially in ( 'arrick and (lalloway, where 

 the highest point ( Merrick, 2764 feet ) of the southern 

 upland* is reached. The Silurian strata are over- 

 laid towards the south by younger I'al.-i -o/oic rock**, 

 consisting principally of sandstone and igneous 

 rocks which gave rise to different orographic feat- 

 ures. Thus we have the broad vale of Tweed and 

 the lower reaches of Teviotdalc occupied chiefly by 

 sandstones and shales. The Cheviot Hills, again, 

 are built up in the north-east chiefly of bedded 

 igneous rocks which towards the south-west give 

 place to sandstones that form broad elevated moors 

 and serve to connect the Cheviot Hills with the 

 loftier Silurian uplands lying t<> the north-west. In 

 this region of sandstones, &c., not a few of the hills 

 are conical in shape a form due to the presence 

 of cappings of relatively harder igneous rocks. 



Crossing the borders of Scotland and England 

 we find the high ground just referred to is con- 

 tinued southwards through Northumberland, Cum- 

 berland, Durham, Yorkshire, Lancashire, and 

 Derbyshire to form what is called the Pennine 

 Chain. This 'chain' varies in height from 1200 

 to 3000 feet, reaching its highest summit in Scafell 

 Pike, Cumberland, which is 3210 feet high. When 

 the hills are composed chiefly of sandstones and 

 shales, they show generally a somewhat rounded 

 and monotonous outline, but in the regions where 

 thick limestones abound these usually give rise to 

 more or less bold and abrupt escarpments. The 

 Lake district of Cumberland and \Vestniorland, 

 being built up mainly of Silurian rocks, reproduces 

 the characteristic features of the southern uplands 

 of Scotland. And the same is to a large extent 

 true of the mountainous parts of Wales (whose 

 highest point, Snowdon, is 3571 feet), while not 

 a few of the features of the Scottish Highlands 

 reappear on a small scale in Devonshire and Corn- 

 wall. All these hillier tracts are composed essenti- 

 ally of Palseozoic and associated igneous rocks. 

 The major portion of England, however, consists 

 principally of younger strata, and may be con- 

 sidered on the whole as a somewhat undulating 

 plain traversed by ridges of varying elevation, 

 which trend in a general direction from north-east 

 to south-west. The band of Jurassic strata, extend- 

 ing from the Yorkshire Moors south and south- 

 west to the coast of Dorset, forms a tortuous belt 

 of tableland and escarpment, rising sometimes to 

 a height of 1500 feet, and throughout its course pre- 

 senting usually a bold face to the west and a gentle 

 slope to the east. This configuration is the result 

 of geological structure the escarpments corre- 

 sponding to the outcrop of the relatively harder 

 members of the Jurassic system, which are under- 

 laid and overlaid of more readily eroded strata, 

 while the general inclination of the strata is to the 

 east and south-east. Similar escarpments accom- 

 pany the outcrop of the chalk, but tney are neither 

 so lofty nor so bold. They form the Wolds of 

 Yorkshire and Lincoln, and rise into a low range 

 of hills that extend from Norfolk to Wilts, the 

 more prominent portions of which are known a-s 

 the Chiltern Hills, the Marlborough Downs, and 

 Salisbury Plain. On the north and south side of 

 the Wealden anticlinal axis, similar chalk hills 

 appear, forming the North Downs in Surrey and 

 Kent, and the South Downs in Hants and Sussex. 

 Lyinj between the Pennine Chain in the west, and 

 the Yorkshire Moors and Wolds and Lincoln 

 Heights and Wolds in the east, lies the broad de- 

 pression traveled by the Ouse and Trent which is 

 occupied chiefly by Triassic strata. In like manner, 

 a low plain separates the mountain-tracts of Wales 

 from tne Pennine Chain, which is similarly occupied 

 by Triassic and younger Palieozoic strata. The 

 maritime parts of Lincoln, Norfolk, Suffolk, Essex. 



