Page:Encyclopædia Britannica, Ninth Edition, v. 17.djvu/618

566 NORTHUMBERLAND planes of bedding (perhaps at the close of the Carbon iferous period) forms the crag -making line of the Great Whinsill, which, with many shifts, breaks, and gaps, ex tends from Greenhead near Gilsland to the Kyloe Hills. Numbers of basalt dykes cross the county, and were prob ably connected with the plateau of Miocene volcanic rocks in the Hebrides. Everywhere the Glacial period has left rocks rounded and scored, and rock-fragments from far and near rubbed up into boulder-clay. The glaciers at first held with the valleys, but as the ice-inundation grew they spread out into one sheet, the Cheviot tops, heavily ice-capped, alone rising above it. Two great currents met in con fluence around these hills, one from across the western watershed, the other skirting the coast from the north. Boulders from Galloway, Criffel, the English lake district, and other places adjacent, and from the Lammermuirs and Berwickshire, lie in their track. Of moraines there are only a few towards the hills. The " great submergence " has left no unequivocal signs of its presence. Glaciated shell-fragments have been detected at Tynemouth. Lami nated brick clays occur among the boulder-clays. Sheets and mounds of gravel of the nature of kames exist here and there on the low grounds, and stretch in a chain over the low watershed between Haltwhistle and Gilsland, sparsely dotting also some more upland valleys. An upper boulder-clay, containing flints, skirts the coast. The older valleys are all pre-Glacial, and may date from the Miocene period. They are much choked up with Glacial deposits, and lie so deep below the surface that, if they were cleared-out arms of the sea, one of them, 140 feet deep at Newcastle, would extend for miles inland. After the departure of the glaciers the streams here and there wandered into new positions, and hence arises a great variety of smooth slope and rocky gorge. In the open country atmospheric waste has hollowed out the shales at their outcrops, leaving the sandstones, &c., as protruding " edges," roughened here and there into crags. In the lower grounds, where this surf ace -dissection first began, the " edges " have much run together ; on the heights, whose turn came last, they are often prominent and crest-like, but have glacier-rounded brows. Many old tarns are now sheeted over with peat. The sloping peat-fields are often the sites of straggling birch-woods, now buried. Minerals, &c. The main portion of the great northern coal-field that extends into Northumberland is an uneven triangle, with its base stretching 14 miles inland from the mouth of the Tyne, and its apex on the coast 24 miles northwards. There are eighteen or twenty seams of work able thickness, all of them of varieties known as bituminous or " caking " coal, amounting in the aggregate to nearly 60 feet in thickness. The familiar " Wallsend" was the product of a seam now worked out (the High Main), and its name has sunk into a trade term. The Low Main or Hutton seam ranks first in thickness and value ; it runs nearly through the whole length of the northern coal-field, and yields at one point or another the best description of three varieties of coal, viz., household, gas, and steam coals, in Northum berland chiefly steam coal. The seams below it, including five seams averaging about a yard in thickness, are still unworked at Newcastle. The best coking coals are fur nished from the lower seams. Three little coal-basins lie against a fault on the moors south of the Tyne. In the Limestone series there also exist coal-seams of some value, worked here and there, generally singly and for land sale purposes. The Scremerston lower coals, eight of which are workable seams with an aggregate thickness of 23 feet, form a little coal-field in the Carbonaceous group in the north of the county. Numberless little seams are dug into by farmers and shepherds for their own use, chiefly in the same group in the southern half of the county. According to the mineral statistics the output of coal from the 176 collieries worked in Northumberland in 1882 was 14,518,789 tons, as against 36,299,597 tons from the whole coal-field, and 156,499,977 tons from the United Kingdom. The net quantity of coal in Northumberland available for the future was estimated before the Coal Commission in 1870 as 2,576,000,000 tons, besides 403,000,000 tons under the sea within 2 miles of land. About 350 millions of tons have since been realized. The rate of production is increasing annually. The "lead-measures" in Northumberland chiefly lie in South Tynedale and Allendale, and belong to the Upper Limestone series or Yoredale rocks. From these lead- mines in 1882 there were raised 6817 tons of ore, having a value of 54,719. The product of the ore was 5252 tons of lead and 9547 ounces of silver. The industry has recently suffered from the effects of foreign competition. The Cleveland ironstone and cheap foreign import have repressed iron-mining in Northumberland. An abundance of nodular calcareous ironstone in the Upper Limestone series awaits future development. For many years a shale bed at Redesdale furnished Sir W. G. Armstrong with some of his best materials, but it was abandoned in 1877. Among other mineral products are building freestones in profusion ; millstone grits, not at all restricted to the strata bearing the name ; fireclays, chiefly of value among the Coal-measures ; brick clays from glacial beds ; and disin tegrated shales. The Whinsill yields hard paving-stones and kerbstones ; Newcastle grindstones, from a hard sand stone near the town, are as familiar as " Wallsend " ; and limekilns are numerous in the broad belt occupied by the upper limestones. The uplands are rich in springs issuing from the sandstones and limestones. Chalybeate springs or "red wells" abound; "sulphur wells" (sulphuretted hydrogen) are by no means rare. Natural History. The fauna and flora of the county have been worked out with a care and completeness chiefly due to the Naturalists Field Clubs of Tyneside and Ber wickshire. The catalogue of plants in Northumberland (with Durham) contains 936 species out of the 1425 of the British list, Ireland excluded. The facies of the flora is intermediate between the northern and southern types of the island. Forty-six species enter Northumberland from the south which do not reach Scotland. There is a distinct preponderance of damp-loving kinds. No plants are restricted to the county. Numerous aliens, enume rated as 1 17 species, grow upon the large ballast-hills beside the Tyne and elsewhere, and there are 87 other " casual introductions." The cloudberry ripens on most of the watershed hills above 1250 feet. The richness of bird-life in the county is accounted for by the situation of the coast in a frequented track of migration to and from the north, and by the diversity of its own phy sical features. Of the entire catalogue of British birds, in all about 395 species, two-thirds (267) have been met in Northumberland and Durham, 91 of which are residents, 40 spring and autumn migrants that come to nest, 54 autumn and winter visitants, and 79 casual visitants. Moorfowl abound on the fells, though less numerously than of old. Among the larger fauna of the county are the half-wild white cattle of Chillingham Park, the representatives, ac cording to the best authorities, of the aboriginal cattle of the British forests, and degenerated descendants of the great Urus, or Bos primigenius. Climate. The climate is bracing and healthy. In spring east winds prevail over the whole county. The lambing season in the higher uplands is fixed for the latter half of April, and is even then often too early. In summer and autumn west winds are general. The mean temperature in the shade at Alnwick and North Shields in the winter and summer quarters of the year, dur ing four years of observation, was as follows : Alnwick, summer