The watershed of the southern Uplands runs from the mouth of Loch Ryan in a sinuous north-easterly direction, keeping near the northern limit of the region till it reaches the basin of the Nith, where it quits the Uplands, descends into the lowlands of Ayrshire, and, after circling round the headwaters of the Nith, strikes south-eastwards across half the breadth of the Uplands, then sweeps north and eastwards between the basins of the Clyde, Tweed and Annan, and then through the moors that surround the sources of the Ettrick, Teviot and Jed, into the Cheviot hills.
Here, again, the longest slope is on the east side, where the Tweed bears the whole drainage of that side into the sea. Although the rocks throughout the southern Uplands have a persistent north-easterly and south-westerly strike, and though this trend is apparent in the bands of more rugged hills that mark the out crop of hard grits and greywackes, nevertheless geological structure has been much less effective in determining the lines of ridge and valley than in the Highlands. On the southern side of the watershed, in Dumfriesshire and Galloway, the valleys run generally transversely from north-west to south-east. But in the eastern half of the Uplands the valleys do not appear to have any relation to the geological structure of the ground underneath.
In the southern Uplands, owing to the greater softness and uniformity of texture of the rocks, as compared with those of the Highlands, rock-tarns are comparatively infrequent, except in Galloway, where the protrusion of granite and its associated metamorphism have reproduced Highland conditions of rock structure. The best known and one of the most picturesque of moraine-dammed lochs is the wild and lonely Loch Skene, lying in a recess of Whitecoombe at the head of Moffat water. Others are sprinkled over the higher parts of the valleys in Galloway.
On the east the southern uplands plunge abruptly into the sea near St. Abb's head in a noble range of precipices 30o to 500 ft. in height, and on the west terminate in a long broken line of sea-wall, which begins at the mouth of Loch Ryan, extends to the Mull of Galloway and reappears again in the southern headlands of Wigtown and Kirkcudbright. Southward they sink to the narrow Lowland bordering Solway firth.
On the grassy hills of the Uplands, from end to end, sheep farming is naturally an outstanding occupation, and with it is associated the woollen industry centred in the chief inland towns of the Tweed basin. In the west (Galloway, Ayrshire)
dairy farming is highly developed for the supply of the neigh bouring populous centres in the Lowlands. Into the western dales, too, some of the industries of the Lowlands extend, with some coal-mining in Nithsdale, quarrying of freestone, etc., while the granite of Creetown and the neighbourhood is famous. But, as a whole, the human, like the physical, geography of the southern Uplands, is clearly differentiated from that of the Highlands and the Lowlands ; it approaches more nearly in character to that of our north-eastern region. (0. J. R. H.) Scotland lies in the course of a pre-Devonian mountain chain that stretches from Scandinavia to Ireland. This chain, called Caledonian by Suess, dominates the early geological history of the country. The general course of its structures is north-east south-west. Its foreland is in the Outer Hebrides, its front in the north-west Highlands. Its latest manifestation is the cor rugation of the Silurian of the Southern Uplands—where Lap worth demonstrated the true worth of graptolites.
Pre-Devonian of the North-west Highlands and Islands. —The oldest rocks are grouped as Lewisian Complex. They make the greater part of Lewis, with its companion Outer Hebrides, and much of the coast of the adjacent mainland. Apparently, their earliest members consist of metamorphic sediments, in cluding magnesian marbles and graphitic schists. Into these are intruded igneous gneisses (intermediate, basic, etc.). Lo cally, late dykes of the complex have escaped metamorphism. The Lewisian abounds in records of pre-Torridonian movements executed under diverse conditions. Two phenomena have at tracted particular attention : transformation of dolerite into horn blende-schist, and production by frictional fusion of so-called "flinty" crush-rock. A great development of "flinty" crush rock follows an east-south-eastwardly inclined thrust-plane along the Outer Hebrides.
Torridonian succeeds Lewisian with complete unconformity. From Islay northward to Skye, the Lower Torridonian basal con glomerates, epidotic grits, grey sandstones, flags and grey and black shales reach a collective thickness of 7,00o feet. Farther north, Middle Torridonian arkose (6,000-8,000 ft.), with local breccias, rests among and covers over "fossil hills" of Lewisian gneiss which are sometimes more than 2,000 ft. in individual height. Upper Torridonian sandstones, flags and shales attain 4,500 feet.