Hampshire into Sussex, where it forms the celebrated sheep-walk of the South Downs, and terminates on the coast at Beachy Head. A second range intersects the north of Hampshire, and passes centrally through Surrey into Kent, where it is known as the North Downs, terminating on its eastern coast. From Guildford to near Farnham, this ridge bears the name of the Hog's-Back, being continuous and narrow; and southward, the lower green-sand of the chalk series occupying the surface, forms an excessively dreary district, producing only fern, heath, and furze. "In crossing this desolate region by the main road from London to Portsmouth, it is difficult to believe that we are only forty miles distant from the capital, and midway to one of the chief naval establishments of the empire; but the nature of the soil effectually prevents improvement, and it is not improbable that this tract may remain for centuries unchanged, and still exemplify the power of geological causes in modifying the civil condition of countries, as well as their external features."-Geog. Trans. The North and South Downs inclose in those directions the Weald of Kent, Surrey, and Sussex,-apparently, when viewed from the adjoining hills, an extensive level, though an undulating country, retaining in towering oaks monuments of its ancient forest, which in Caxton's time, who learnt his " English in the Weald," was "stored and stuffed with herds of deer and droves of hogs." A third and more important range, diverging from Salisbury Plain, follows a wavy course into Norfolk, taking the name of the Chiltern Hills in Oxfordshire, and the Gogmagog Hills in Cambridgeshire, greatly declining in height towards the eastern counties.

Other elevations in the central and eastern counties of England are Bar Beacon, N. of Birmingham, 653 feet; Castle Ring, W. of Lichfield, 715; Bardon Hill, W.N.W. of Leicester, 853; Arbury Hill, Northamptonshire, 804; Apwell Hill, near the north point of Oxfordshire, 836; and High Beech, in Essex, N.N.E. of London, 750 feet. At great distances from the sea the rivers are only at a small height above low-water mark, showing the slight elevation of the general surface: Nen, at Northampton, 198 feet; Ouse, at Buckingham, 265; Trent, at Trentbridge, near Nottingham, 73; Derwent, at Derby, 172; Trent, at its junction with the Thame, Staffordshire, 188; Avon, Northamptonshire, where it is traversed by the London and North Western Railway, 242; Thames, at Lechlade, border of Gloucestershire, 243; Soar, at Leicester, 186; and Rea, at Birmingham, 330 feet. The greatest extent of low land lies around the estuary of the Wash, comprising portions of the counties of Lincoln, Norfolk, Cambridge, Huntingdon, and Northampton, which form the country specially styled the Fens. This district may be defined generally by a line drawn from Wainfleet on the Lincolnshire coast W. to Tatershall, running from thence S.W. to Sleaford, S. towards Huntingdon, and proceeding along the right bank of the Ouse to its mouth at Lynn. It extends north and south about 50 miles, and 30 miles east and west, where the breadth is the greatest, between Lynn and Market Deeping. The area is stated to contain 700,000 acres. Much the larger portion belongs to Lincolnshire, and includes the whole of that division of the county appropriately called Holland, hollow or low land, resembling in its physical features the Dutch province of that name. The great amount of land water which flows to the Wash, the very slight fall of the rivers, and the lowland character of the country, expose it to floods from sudden falls of rain, and also to inundations of the sea, requiring a network of artificial channels, with windmills and steam-power, to promote drainage and keep the waters in check. A similar tract, mostly below high-water mark, occupies a portion of Yorkshire and Lincolnshire between the Don, Ouse, and Trent. Romney Marsh, also a low fertile plain at the south-east angle of Kent, is only prevented from being overflowed at high-water by the immense embankment of Dymechurch Wall.

NORTH BRITAIN consists of three natural divisions,-the Southern, Central, and Northern, each containing highlands and lowlands.

The South Division of Scotland extends from the English border to the great hollow occupied by the Firths of Forth and Clyde, and the narrow plain traversed by the canal which unites the two estuaries. Its mountain system, sufficiently bold to be denominated the Southern Highlands, includes the Cheviots, on the border, with their protruding masses in Northumberland, but is principally developed in the great central nucleus of the Lowther Hills, near the junction of the counties of Dumfries, Lanark, Peebles, and Selkirk, connected by offsets with the south and east coasts. The Pentland Hills, running S.W. from the neighbourhood of Edinburgh, and the Lammermoor and Moorfoot Hills, following the same direction inland from St. Abb's Head, are detached secondary ranges. The chief lowlands are,-the basin of Ayrshire, the valley of the Clyde, the rich vale of the Haddingtonshire Tyne, the Merse of Berwickshire, the low country north of the Solway, and the pastoral straths of Nithsdale, Annandale, Eskdale, and Teviotdale.

The Central District of Scotland extends from the isthmus of the Forth and Clyde to the remark

able Glenmore-nan-Albin, or Great Glen of Scotland, which runs N.E. from Loch Linnhe to the Murray Firth, and is traversed by a chain of lakes connected by the line of the Caledonian Canal, uniting the Atlantic and North Sea. A vast extent of this region is occupied by mountains comprising the highest summits of the United Kingdom. The grand chain of the Central Grampians stretches across the island from the coast of Aberdeenshire, and enormous masses spread over the western side southwards, towards the estuary of the Clyde, sometimes called the southern Grampians. Parallel to the central chain, but at some distance, an inferior range extends with interruptions from coast to coast, taking the name of the Sidlaw Hills from Montrose to Perth, the Ochil Hills from thence to the River Forth, and the Campsie Hills in Stirlingshire. Between this range and the Grampians is Strathmore, or the Great Valley, the most extensive of the Scottish lowlands. Other lowland tracts are, the Carse of Gowrie, between the Sidlaw Hills and the estuary of the Tay; and the How of Fife, along the course of the Eden in Fifeshire.

The North Division of Scotland, extending from the Great Glen to the Pentland Firth, has the most mountainous and barren surface, though not reaching to the elevation of the Grampians; the productive lowlands being chiefly confined to the borders of the eastern firths.

The mountains in the islands of Scotland may be regarded as insular continuations of the mainland ranges, generally of moderate elevation.

In contrasting North and South Britain, the predominant highland aspect of the former, and the prevailing lowland character of the latter, are not the only points of difference. The geological composition of the surface is remarkably distinct. Granite, trappean, and other igneous rocks, occur in great force in Scotland, and very sparingly south of the border. Metamorphic masses, gneiss, and mica-slate, comprise nearly half the surface of Scotland; while, excepting unimportant examples in Cumberland, there is hardly any real gneiss or mica-slate in England and Wales. On the other hand, the formations more recent than the carboniferous epoch, which in England cover about two-thirds of the country, are in Scotland only represented by a few detached patches of oolite, of wholly insignificant extent.

Ireland has its general physiognomy determined by a great central plain, extending across the island from Dublin to Galway Bay, and from the county of Fermanagh on the north to the borders of Waterford on the south. This great tract is far from being a dead level, but diversified with hills and valleys, though its most elevated point, Moat-a-grenogue, in Westmeath, is little more than 300 feet above the level of the sea. A large proportion of its area is occupied with flat red bogs, denominated from their reddish tinge, consisting of decomposed vegetable matter, covered with unproductive living vegetation, holding more or less stagnant water. Imposing highlands occur external to the plain, or on the borders, throwing out spurs into it; but the mountain masses constitute detached ranges, and groups of limited extent, and not a continuous belt, though largely cutting off the low country from the coasts.

INLAND WATERS.

RIVERS.-The surface of Great Britain comprises six hydrographical regions, defined by the waterparting between rivers flowing off in opposite directions, and proceeding to different basins, or communicating at distant points with the same basin. These systems of drainage may be respectively denominated :—the Eastern, by far the most important, consisting of the entire east of England and Scotland, with a large portion of the central districts, connected with the German Ocean; the Southern, embracing the counties, in whole or in part, which border the English Channel; the SouthWestern, extending from north Northamptonshire to the Severn estuary, and including the principal part of Wales, with the country on both sides of the Bristol Channel to the Land's End and St. David's Head; the Western, comprising the west of Wales, the north of the principality, and those parts of England and Scotland which are contiguous to the Irish Sea; the North-Western, embracing the west of Scotland, communicating its waters to the Atlantic; and the Northern, an insignificant portion of the north extremity of Scotland, sending off a few streams in an opposite direction, northward, to the same basin. Ireland has four similar hydrographical regions; an eastern system of drainage, the least important, belonging to the Irish Sea; the remainder of the surface sloping northward and southward, but principally westward, to the Atlantic.

The Humber, including Trent and Ouse, is the largest river of the British Islands in regard to the area of its basin, which is equal to nearly one-sixth of the total area of England and Wales. The waters of the upper and lower Trent run in exactly opposite directions, from north to south, and from south to north.

The Severn, ranking second in the magnitude of its basin, is the first in point of length, the distance along this river being about twice the direct distance from source to mouth, owing to its curvilinear course.

The Shannon is superior to all other British rivers in the length of its navigation, which extends to Lough Allen, 213 miles from its mouth, that of the Severn extending to Welshpool 192, and of the Thames to Lechlade, 193 miles from their mouths. The fall of the Shannon exhibits a rare exception to the general fall of rivers, being the greatest in the lower part of its course. From Lough Allen to Lough Dearg, a distance of 131 miles, it descends only at the rate of 4 inches per mile, but from Castle Connel to Castle Troy, between Lough Dearg and Limerick, the descent amounts to nearly 17 feet per mile, the river forming in this part of its course the magnificent rapids of Doonas, where the navigation is conducted by artificial cuts.

The Thames, commercially the most important river of the globe, is only the fourth in point of magnitude belonging to the United Kingdom, but it ranks first as a tidal river. The tidewater extends about 64 miles, from the Nore Light to Teddington (Tydington). The time of high water at Teddington Lock is about two hours later than at London Bridge. Between Westminster and London Bridge, the mean velocities of flood and ebb are 3 miles per hour, extreme 3; ebb 3, extreme 3.

The Avon and Nen-the Calder branch of the Ribble, and the stream of the same name which belongs to the system of the Humber-the Eden, and the Swale and Ure which form the Yorkshire Ouse-the Tweed and Clyde-are examples of rivers having closely contiguous sources, and flowing off to opposite seas. The Tweed and Clyde occasionally exhibit an instance of bifurcation, explained as follows:-" It is a singular circumstance, that salmon and their fry have occasionally been taken in the upper parts of the Clyde, above its loftiest fall, which being 80 feet in height, it is utterly impossible for fish of any kind to surmount. The fact is accounted for in this way. After passing Tinto Hill, the bed of the Clyde approaches to a level with that of the Biggar Water, which is close at hand, and which discharges itself into the Tweed. On the occasion of a large flood, the two streams become connected, and the Clyde actually pours a portion of its waters into one of the tributaries of the Tweed, which is accessible to and frequented by salmon."

The Tay, the monarch of Scottish streams, is remarkable for the immense volume of water it discharges into the sea, amounting in a mean state to 218,159 cubic feet per minute, as ascertained by a careful measurement of Dr. Anderson. Its tributaries exhibit an epitome of everything connected with the action of running water, the erosion of rocks, the origin of river-valleys, and the changes they undergo. In Breadalbane, the Dochart may be observed filling up the lake of that name, and at Killin sawing down the rocks which form the cataract; a process, which, if more rapid, might anticipate the former, and drain the lake before its conversion into an alluvial plain. "The deep ravines of the Keltie prove the immense power of even inconsiderable streams acting through long periods, also shown by the Tumel, whose retrogression in its lower cataracts is a picture of that of Niagara, as the wide valley above Birnam Pass shows what Lake Erie is destined to become when that mighty torrent has cut its way backward to it."-Nicol's Geol. of Scotland.

The Dee of Aberdeenshire has the greatest descent of the British rivers, taking its rise from a well or spring at the height of 400 feet on Mount Braerich, one of the Cairngorm group.

The Spey, in the lower parts of its course, is remarkable for its rapid current, whilst in the upper it slumbers in dark mossy lakes.

The British rivers present a few examples of a subterranean flow. The Alyn, an affluent of the Welsh Dee, after breaking through the Flintshire hills, passes through a subterraneous passage for the distance of rather less than a mile, and then enters the plain of Cheshire. In Glamorganshire, the Melte runs for nearly a quarter of a mile through the dark hollow of the Cwm Porth, while cattle graze and harvests wave upon the incumbent rock. Near Wells, in Somersetshire, in the limestone of the Mendip Hills, a three-chambered cavern occurs, with a fine stream running through the farther end, which sinks through a cleft of the rock, and bursts out in the adjoining valley as the source of the north Axe. The Aire, an affluent of the Yorkshire Ouse, has its source probably in Malham Tarn in Craven, but runs underground for about a mile, and issues at the base of the lofty amphitheatre of limestone rocks, called Malham Cove. The Hamps and Manifold, two small streams on the borders of Derbyshire and Staffordshire, belonging to the system of the Trent, sink into the disjointed limestone strata of the district, and after running underground for several miles emerge in the vicinity of Ilam Hall. In the west of Ireland, several lakes with affluents, but without apparent outlets, probably cast off their surplus waters by subterranean channels. Lough Mask has a subterraneous communication with Lough Corrib through the narrow isthmus between them. In that locality several considerable

streams dip underground, sink and emerge frequently, and finally disappear without any visible outlet.

LAKES.-The examples of any importance in England are in the north-west mountain region, where, though numerous, they are more remarkable for picturesque beauty than for magnitude. Wales contains a great number of highland pools and tarns, with two more considerable expanses, Llyn Tegid or Bala Pool in the north, and Llyn Safadhu, or Brecknock-mere, in the south. Scotland and Ireland are eminently lacustrine. The Scotch lakes are mostly long, narrow, and confined, occupying hollows between the mountains, the length far exceeding the breadth. The Irish lakes are upon a larger scale, and have their length and breadth more proportionate.

WATERFALLS.-There are several fine falls in the lake district of England, Wales, the Highlands of Scotland, and the mountain regions of Ireland; in a few instances forming magnificent cataracts by their height or volume of water :—

The confluence of streams, an interesting and often an imposing physical incident, is nowhere in the British Isles displayed under circumstances of greater attraction, than in the basin of the Ovoca, Wicklow. The spot where that river is formed by the junction of the Avonmore and Avonbeg, called the first "Meeting of the Waters," a few miles south of Rathdrum, is a scene of great beauty, inclosed by high grounds covered with fine natural woods, which command magnificent views of the Wicklow Mountains. From the confluence, the Ovoca winds through the loveliest valley in Ireland, between high banks adorned with an unbroken range of forest, to its union with the Aughrim, a stream descending through a glen from the base of Lugnaquilla, constituting the second "Meeting of the Waters."

CLIMATE.

TEMPERATURE.-The physical circumstances which determine the moderate and uniform temperature of Western Europe, compared with the continental climates of the northern hemisphere in corresponding latitudes, may be described as follows:-The British archipelago, from its geographical position, experiences a temperature at least 20° warmer, and ranging to far inferior degrees of heat and cold than would be the case if the great valley of the North Atlantic were to be filled up, and Europe to be connected with America, the prevailing south-west winds thus sweeping across a continent instead of travelling over the warm waters of the Gulf Stream.

..

This produces a difference of 7·08 in the mean temperature of the year at Unst in the Shetlands, at the extreme north of Great Britain, and at Penzance in the extreme south, mainly due to difference of latitude. In a few instances, a considerable discrepancy appears in the temperature of places in very nearly the same latitude, and at a corresponding elevation above the sea level. Exeter and Gosport furnish an example, the former place being 5.07 colder than the latter. This is no doubt caused by the warm south-west winds reaching Gosport without passing over elevated land, and

having their temperature diminished by the high granitic plateau of Dartmoor, on their passage to Exeter.

The more temperate character of the climate of the kingdom may be strikingly exhibited by a comparison of mean annual temperatures given in round numbers, between British and Continental places, at latitudes closely corresponding, and at elevations above the sea marked with no important difference:

In the east of North America, the zone of perpetually frozen subsoil descends to a distance from the equator parallel to that of the vale of York in Britain, and in Central Asia corresponding to that of the north bank of the Thames.

The least difference between the summer and winter mean in Great Britain, or the nearest approach to equality in the distribution of temperature, occurs at the opposite extremities, Unst, Stromness, and Wick in the north, Truro, Falmouth, and Penzance, in the south. These are specially maritime sites, with minima extremes of heat and cold, in summer and winter, by day and by night, one of the features discriminating maritime from continental climates.

The same places, Unst, Stromness, and Wick, in the north, Truro, Falmouth, and Penzance, in the south, exhibit the least difference of temperature between their coldest and hottest months. The difference for Great Britain at a mean is about 24°, which becomes more excessive in proportion as we recede from it eastward into the interior of Europe and Asia, observing a corresponding latitude, the coldest and hottest months varying in their temperature 34° at Hamburg, 41° at Brunswick, 38° at Berlin, 39° at New Strelitz, 37° at Stralsund, 41° at Christiana, and 57° at St. Petersburg. It may be reasonably concluded that the operations so largely carried on by human industry, such as the removal of the natural forests, draining, inclosing, and planting, have not been without their effect upon the climate; but the general temperature has probably not been altered to any appreciable extent within the historic period, only its distribution become more equable, summer heat and winter cold not so strongly contrasting now as formerly.

The most striking feature in the distribution of temperature in the British Isles is the general direction of the isothermals of the coldest month north and south, instead of east and west, indicating little or no difference in the winter temperature northward and southward, but a greater degree of cold from west to east. Though Unst is 10° of latitude farther north than Chichester, their winter temperature is about the same. On the other hand, passing from Penzance eastward to Chichester and London, we encounter a temperature about 6° lower in the coldest month in the latter places than at the former. Comparing the extreme limits of the United Kingdom together, it is probable that the eastern coasts of England experience a winter temperature nearly 10° colder than the western coasts of Ireland, a distance of about 500 miles subsisting between them; while there is no sensible difference in the same respect between the northernmost of the Shetlands and the Isle of Wight, the intervening distance amounting to 700 miles. The coldest portion of the kingdom, which is included within the isotherm of 36°, extends along the east coast of Great Britain from the Naze in Essex to the Firth of Forth, and comprehends the counties of Suffolk, Norfolk, Lincoln, Nottingham, Derby, York, great part of Westmoreland, Durham, Northumberland, Roxburgh, Selkirk, Peebles, and Berwick. The obvious cause of the higher temperature of the coldest month on proceeding from the east of Great Britain to the west of Ireland is the greater influence of the westerly winds, and proximity to the Gulf Stream. In a similar manner, on passing to the continent, the coldest month exhibits a gradually lower temperature as we proceed easterly— Berlin, in a corresponding latitude to Boston, being 9° colder.

The isothermals of the hottest month have their average direction from south-west to north-east. The highest summer temperature, indicated by the isotherm of 64°, distinguishes a portion of the south of England, including the counties of Dorset and Somerset, with parts of Hants, Devon, Wilts, and Gloucester, extending over the Bristol Channel to Swansea. The next warmest region, included