GREAT BRITAIN. Under this head are noticed-1. The island of Great Britain— its geology and geography; 2. The United Kingdom of Great Britain and Ireland—its general statistics, etc. Historical sketches of England and Scotland down to the union of the two kingdoms are given under their respective names; the history of Ireland to its union with Great Britain is also given under its own name, together with its geography.
The IsI,AND or GREAT BRITAIN—so called to distinguish it from Britannia Minor, or Little Britain Ig•e BriETA6x10 in France—lies between lat. 49°`57' 30" and 58° 40' 24' n., and between long. 46' e. and 13' w., and is the largest island in Europe. It is bounded on the n. by the Atlantic, on the e. by the North sea, on the s. by the English channel, and on the w. by the Atlantic, the Irish sea, and St. George's channel. The most northerly point, is Dunnet head, iu Caithness; the most southerly, Lizard point, in Cornwall; the most easterly, Lowestoft Ness, in Suffolk; and the most west erly, Ardaamurchan point, in Argyleshire. Its greatest length is about 603 in., and its greatest breadth (from Land's End to the e. coast of Kent) about 320 in. ; while its sur face contains about 80,600 sq. miles.
Ceology.—The geology of Great Britain is of peculiar importance. The rocks of the earth's crust having first systematically studied and expounded here, British geologists have given to the world the names whereby the various strata' are known, and British rocks form the typical series of the earth's strata. The whole recognized series of Stratified deposits occur in Britain, one or two only being more oped elsewhere; and it is only in these singular cases that the foreign equivalents are taken as the types. British geology is no less important from the influence it has had in the development of the country. The mineral wealth, especially the coal and the iron, are the real sinews and muscles of Britain's mighty power. No other country has similar advantages in such an urea. • We shall, in this sketch of the distribution of the British rocks, follow the order of the strata, beginning with the lowest and oldest. It may he said that, in general, the mountainous regions of the n, and w. are formed of the oldest sedimentary rocks, and that, as we move south-eastwards, we gradually pass over newer strata, until, in' he e. of England, we come to the only extensive Pleistocene deposits in the country.
The base rocks of the whole series occur in the outer Liebrides, in Time and Coll, and along the western shores of Sutherland and Ross. The true position of these strata has been only recently determined by Murchison and Geikie, who, noticing that their strike was at right angles to the beds resting above them, discovered that they were older than the superimposed Cambrian rocks. . They consider them to be the equiva lents of the Laurentian system, described by sir W. Logan in Canada. The predomi nant rock is crystalline gneiss. A baud of limestone occurs on the n.e. shore of loch Marge, but this has hitherto proved unfossiliferous.
Resting on the convoluted edges of this old gneiss, on the mainland, and forming the basement rocks in Cumberland, Anglesey, and North Wales, we have the Cambrian series of deposits. In Scotland, these rocks are brownish-red sandstones and conglom
erates; in England and Wales, they are composed of sandstones, gritstones, and slates. A few fossils, chiefly impressions of supposed fucoid plants, annelid tracks, and zoo phytes, have been found in the slates.
The Silurian measures occupy a large portion of the surface of the country. The typical rocks occur in Wales, extending over the western portion of the principality from Pembroke to Denbigh, and including the northern portions of Pembroke, Cats marthen, and Brecknock, the whole of Radnor and Montgomery, the s.w. of Denbigh, and the whole of the counties to the west. The oldest or lower silurian beds are next the coast. The series consists of an immense thickness of shales, slates, and sandstones, with intercalated limestones more or less pure: Immense tracts have hitherto proved devoid of fossils; in other districts, the calcareous rocks are almost entirely composed of the remains of marine invertebrate animals, while the shales abound in zoophytes and crustacea. The high lands in the n. of Lancashire and s. of Westmoreland are silurian; but it is in Scotland where these strata are most extensively developed; indeed, almost the svhole country consists of silurian strata, with the exception of a large trough in the center, occupied with newer rocks. A line drawn from Dunbar to Girvan forms the northern limit of these beds in the s. of Scotland. Except the lower half of the valley of the Tweed, the whole region from this line to near the base of the Chevi ots is silurian, The rocks are chiefly graywacke; with scattered beds of impure lime stone. The chief fossils are graptolites, crustacea, and mollusea. The lead-mines of Wardockhead and Leadbills are in this district. A line drawn from Stonehaven to Ilelensburgh would mark the termination of the silurian strata, which compose the whole of the n. of Scotland. with the exception of the. newer beds on the n.e. coast, and the Laurentian and Cambrian series already described. All the series is greatly metamorphosed; the lower strata are converted into quartzose flagstones and quartz rock, the upper into chlorite and mica-slate, and quartzose and gneissose rocks.
The old red sandstone strata, consisting of conglomerates, coarse and fine grained sandstones, and dark-colored schists, with the characteristic fossils of ganoid and placoid fish. overlie the silurians in 'several districts in Scotland. Nearly all Caithness and the seaward portions of Sutherland, Ross, Cromarty, Inverness, Nairn, and Moray, belong to these strata. A broad band, rising on the e. coast between Stonehaven and St. Andrews, stretches across the country to Helensburgh and Dumbarton on the west. The same strata appear again in Haddington, Berwick, and Roxburgh, in Lanark, and iu Ayrshire. An extensive tract of these strata occurs in South Wales and the neigh boring English counties, extending from the Silurian district to the Severn and the Bristol channel, and containing in ti large basin the South Wales coal-field. The highly fossiliferous strata of .North Devon, and of South Devon and Cornwall, belong to thin