Page:Encyclopædia Britannica, Ninth Edition, v. 17.djvu/617

NORTHUMBERLAND 565 nature into two groups. What may be called the northern Cheviots are green hills of conical and high-arched forms, finely grouped, with the peat-capped Cheviot itself (2676 feet) at their centre, deep steep glens radiating into all parts of their mass, and generally more or less of hollow and enclosed ground separating them from the slopes at their base. The southern Cheviots (south-westwards from Thirl- moor) are the highest part of the county, moory hills, lower and more confluent, and sometimes curiously equal- topped. On the Cumberland side of the county these watershed heights sink into a monotonous rolling tract, separated only by the river Irthing from the "wastes" of Bewcastle. They again swell up in the south-west towards Killhope Law (2208 feet) and the Pennine range. Few eminences break the general incline, which stretches in a far-spread billowy sea of confluent hills that for six months of the year mingle their browns, russets, and duns in a pattern of Oriental richness, and at all times communicate a fine sense of altitude and expanse. The Simonside Hills (1447 feet) form one not very conspicuous exception. The configuration of much of these uplands has a certain linearity in its details due to groups and ranges of ridges, crags, and terrace-like tiers, picturesquely termed " edges " (escarp ments) by the country folk, and generally facing the interior, like broad ends of wedges. The line of pillared crags and prow-like headlands between the North and South Tynes along the verge of which the Romans carried their wall is a fine specimen. Passing eastwards from the uplands we exchange the moors for enclosed grounds, " drystone " walls for hedgerows, rare sprinklings of birch for a sufficiently varied wooding, and towards the south-east we approach the smoke of the coal-field and the roar of the Tyne. The chief rivers and valleys are the Derwent, the Irthing, the Tyne (with its North and South branches, the Allendales, and Redesdale), the Wansbeck with its twin the Font, the Coquet, the Alne, the Till with its feeders the Breamish, Glen, and College, and the Tweed. The Tyne is the "coaly Tyne" only from Wylam downwards. For 19 miles (its tidal portion) it has been dredged into a small estuary, "a river of coal, iron, and chemicals." The rivers and streams in general are greatly diversified with numbers of rocky gorges and rich "denes." The deepest glen-scenery is at the head of the Breamish and College burns ; and the North Tyne gathers its waters from surrounding moorlands into a vale of surpassing beauty, The coast is a succession of sands, flat tidal rocks, and low cliffs. Itj bays are edged by blown sandhills ; its borders are s: verely wind-swept. Several islands lie over against it. L-oly Island, the classic Lindisfarne, 1051 acres in extent, but half " links " and sandbanks, is annexed to the mainland and accessible to conveyances every tide. The Fame Islands are a group of rocky islets farther south, the scene of many saintly austerities, and of the nobler devotion of Grace Darling. Geology. The core of the county, in a geological aspect, is the northern Cheviots from Redesdale head nearly to the Tweed. Its oldest rocks are gritty and slaty beds of Silurian age, about the head of the rivers Rede and Coquet and near the Breamish south of Ingram, a part of the great Silurian mass of the southern uplands of Scot land. Even before the times of the Old Red Sandstone these rocks had been crushed and folded, upraised into a continental land, and much wasted. The largest hollows in that ancient continent held the great lakes in which the " Old Red " was deposited. Volcanic activity near one of the lake-group (now to be known as Lake Cheviot) resulted in the felspathic porphyrites passing into the syenites and granites that form the mass of the northern Cheviots. Round this core there now lie relays of Carboniferous strata dipping east and south, much faulted and repeated in places, but passing into Coal-measures and Magnesian Limestone in the south-eastern part of the county. The dawn of the Carboniferous ages saw the volcanic piles of the Cheviots becoming shapeless with waste. Then ensued a general settling down of the land, the gathering of a long series of ^ deposits around its subsiding borders, the burying of Cheviot-land, and the gradual formation of the whole great succession of the Carboniferous system. The builders thereof were three. After every sufficient subsidence the limestone sea that covered Derbyshire sent incursions of marine life northwards ; the waste of the land in the north then spread out in sheets of sand and silt ; and over the mud -flats thus prepared came slow migrations of dense plant -growth. Limestones, sandstones, shales, and coals were the result ; and the whole system now consists of (1) the Carboniferous Limestone series in three divisions, first detected by the accurate eye of George Tate of Alnwick ; (2) the Millstone Grit ; and (3) the Coal-measures. Lowest in Northumberland lies Tate s Tuedian group, the first envelope of sinking Cheviot-land. Some reddish shore-like conglomerates lie in places at its base, as at Roddam Dene ; its shales are often tinged with distemper greens ; its coals are scarcely worthy of the name ; its limestones are thin, except near Rothbury ; and its marine fossils are few and incursive. The Tuedian group is overlaid by the Carbon aceous group ; its shales are carbonaceous-grey, its coals, though mostly small, very numerous, its limestones often plant-limestones, and its calcareous matter much diffused. Upon this lies the Calcareous group ; its lime occurs in well-individualized marine beds, cropping up to the surface in green-vested strips; its fossils are found in recurrent cycles, with the limestones and coals forming their extremes. These three groups now range round the northern Cheviots in curved belts broadening southwards, and occupy nearly all the rolling ground between the Tweed and the South Tyne, the sandstones forming the chief eminences. The middle division becomes thinner and more like the Coal- measures in passing northwards, and the upper division, thinning also, loses many of its limestones. The Millstone Grit is a characterless succession of grits and shales. The Coal-measures possess the same zone-like arrangement that prevails in the Limestone series, but are without limestones. They also are divided, very artificially, into three groups The lowest, from the Brockwell seam downwards, has some traces of Gannister beds, and its coal-seams are but thin. The famous Hutton collection of plants was made chiefly from the roof -shales of two seams, the Bensham and the Low Main. The unique Atthey collection of fishes and Amphibia comes from the latter. The Coal-measures lie along the coast in a long triangle, of which the base, at the Tyne, is produced westwards on to the moors south of that river, where it is wedged against lower beds on the south by a fault. The strata within the triangle give signs of departing from the easterly dip that has brought them where they are, and along a line between its apex (near Amble) and an easterly point in its base (near Jarrow) they turn up north-eastwards, promising coal-crops under the sea. The top of the Coal-measures is wanting. After a slight tilting of the strata and the denudation that removed it, the Permian rocks were deposited, consisting of Magnesian Limestone, a thin fish-bed below it, and yellow sands and some Red Sandstone (with plants of Coal-measure species) at the base. These rocks are now all but removed. They form Tynemouth rock, and lie notched-in against the 90- fathom dyke at Cullercoates, and again are touched (the base only) at Seaton Sluice. No higher strata have been pre served. The chief faults of the county extend across it. Its igneous rocks, other than the Cheviot porphyrites and a few contemporaneous traps in the lowest Carboniferous, are all intrusive. An irregular sheet of basalt forced between