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Originally appearing in Volume V11, Page 638 of the 1911 Encyclopedia Britannica.
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THE PRINCIPLES OF GEOGRAPHY As regards the scope of geography, the order of the various departments and their inter-relation, there is little difference of opinion, and the principles of geography 2 are now generally accepted by modern geographers. The order in which the various subjects are treated in the following sketch is the natural succession from fundamental to dependent facts, which corresponds also to the evolution of the diversities of the earth's crust and of its inhabitants. The fundamental geographical conceptions are mathematical, the relations of space and form. The figure and dimensions of the Mathema- earth are the first of these. They are ascertained by a dal] gee). combination of actual measurement of the highest graphy. precision on the surface and angular observations of the positions of the heavenly bodies. The science of geodesy is part of mathematical geography, of which the arts of surveying and cartography are applications. The motions of the earth as a planet must be taken into account, as they render possible the determination of position and direction by observations of the heavenly bodies. The diurnal rotation of the earth furnishes two fixed points or poles, the axis joining which is fixed or nearly so in its direction in space. The rotation of the earth thus fixes the directions of north and south and defines those of east and west. The angle which the earth's axis makes with the plane in which the planet revolves round the sun determines the varying seasonal distribution of solar radiation over the surface and the mathematical zones of climate. Another important consequence of rotation is the deviation produced in moving bodies relatively to the surface. In the form known as Ferrell's Law this runs: " If a body moves in any direction on the earth's surface, there is a deflecting force which arises from the earth's rotation which tends to deflect it to the right in the northern hemisphere but to the left in the southern hemisphere." The deviation is of importance in the movement of air, of ocean currents, and to some extent of rivers.' In popular usage the words " physical geography " have come to mean geography viewed from a particular standpoint rather Physical than any special department of the subject. The popular geography. meaning is better conveyed by the word physiography, a term which appears to have been introduced by Linnaeus, and was reinvented as a substitute for the cosmography of the middle ages by Professor Huxley. Although the term has since been limited by some writers to one particular part of the subject, it seems best to maintain the original and literal meaning. In the stricter sense, physical geography is that part of geography which involves the processes of contemporary change in the crust and the circulation of the fluid envelopes. It thus draws upon physics for the explanation of the phenomena with the space-relations of which it is specially concerned. Physical geography naturally falls into three divisions, dealing respectively with the surface of the lithosphere—geomorphology; the hydrosphere—oceanography; and the atmosphere—climatology. All these rest upon the facts of mathematical geography, and the three are so closely inter-related that they cannot be rigidly separated in any discussion. Geomorphology is the part of geography which deals with terrestrial relief, including the submarine as well as the subaerial portions of the crust. The history of the origin of the various forms belongs H. Wagner's year-book, Geographische Jahrbuch, published at Gotha, is the best systematic record of the progress of geograph in all departments; and Haack's Geograhhen Kalender, also published annually at Gotha, gives complete lists of the geographical societies and geographers of the world. 2 This phrase is old, appearing in one of the earliest English works on geography, William Cuningham's Cosmographical Glasse conteinyng the pleasant Principles of Cosmographie, Geographie, Hydrographie or Navigation (London, 1559). 3 See also S. Gunther, Handbuch der mathematischen Geographie (Stuttgart, 189o).to geology, and can be completely studied only by geological methods. But the relief of the crust is not a finished piece of sculpture; the forms are for the most part transitional, owing Geomorplitheir characteristic outlines to the process by which they are produced; therefore the geographer must, for strictly otogy geographical purposes, take some account of the processes which are now in action modifying the forms of the crust. Opinion still differs as to the extent to which the geographer's work should overlap that of the geologist. The primary distinction of the forms of the crust is that between elevations and depressions. Granting that the geoid or mean surface of the ocean is a uniform spheroid, the distribution of land and water approximately indicates a division of the surface of the globe into two areas, one of elevation and one of depression. The increasing number of measurements of the height of land in all continents and islands, and the very detailed levellings in those countries which have been thoroughly surveyed, enable the average elevation of the land above sea-level to be fairly estimated, although many vast gaps in accurate knowledge remain, and the estimate is not an exact one. The only part of the sea-bed the configuration of which is at all well known is the zone bordering the coasts where the depth is less than about 100 fathoms or 200 metres, i.e. those parts which sailors speak of as " in soundings." Actual or projected routes for telegraph cables across the deep sea have also been sounded with extreme accuracy in many cases; but beyond these lines of sounding the vast spaces of the ocean remain unplumbed save for the rare researches of scientific expeditions, such as those of the " Challenger," the " Valdivia," the " Albatross " and the " Scotia." Thus the best approximation to the average depth of the ocean is little more than an expert guess; yet a fair approximation is probable for the features of sub-oceanic relief are so much more uniform than those of the land that a smaller number of fixed points is required to determine them. The chief element of uncertainty as to the largest features of the relief of the earth's crust is due to the unexplored area in the Arctic region and the larger regions of the Antarctic, of which Crustal we know nothing. We know that the earth's surface if unveiled of water would exhibit a great region of elevation "lief' arranged with a certain rough radiate symmetry round the north pole, and extending southwards in three unequal arms which taper to points in the south. A depression surrounds the little-known south polar region in a continuous ring and extends northwards in three vast hollows lying between the arms of the elevated area. So far only is it possible to speak with certainty, but it is permissible to take a few steps into the twilight of dawning knowledge and indicate the chief subdivisions which are likely. to be established in the great crust-hollow and the great crust-heap. The boundary between these should obviously be the mean surface of the sphere. Sir John Murray deduced the mean height of the land of the globe as about 2250 ft. above sea-level, and the mean depth of the oceans as 2080 fathoms or 12,48o ft. below sea-level.4 Calculating the area of the land at 55,000,000 sq. m. (or 28.6% of the surface), and that of the oceans as 137,200,000 sq. m. (or 71.4 % of the surface), he found that the volume of the land above sea-level was 23,450,000 cub. m., the volume of water below sea-level 323,800,000, and the total volume of the water equal to about 1th of the volume of the whole globe. From these data, as revised by A. Supan,5 H. R. Mill calculated the position of mean sphere-level at about 1o,000 ft. or 1700 fathoms below sea-level. He showed that an imaginary spheroidal shell, concentric with the earth and cutting the slope between the elevated and depressed areas at the contour-line of 1700 fathoms, would not only leave above it a volume of the crust equal to the volume of the hollow left below it, but would also divide the surface of the earth so that the area of the elevated region was equal to that of the depressed region.6 A similar observation was made almost simultaneously by Romieux,7 who further speculated on the equilibrium between the weight of the elevated land mass and that of the total Areas of waters of the ocean, and deduced some interesting rela- the crust tions between them. Murray, as the result of his study, according divided the earth's surface into three zones—the continental to Murray. area containing all dry land, the transitional area including the submarine slopes down to woo fathoms, and the abysmal area consisting of the floor of the ocean beyond that depth; and Mill proposed to take the line of mean-sphere level, instead of the empirical depth of moo fathoms, as the boundary between the transitional and abysmal areas. An elaborate criticism of all the existing data regarding the volume relations of the vertical relief of the globe was made in 1894 by Professor Hermann Wagner, whose recalculations of volumes ' " On the Height of the Land and the Depth of the Ocean," Scot. Geog. Mag. iv. (1888), p. 1. Estimates had been made previously by Humboldt, De Lapparent, H. Wagner, and subsequently by Penck and Heiderich, and for the oceans by Karstens. 5 Petermanns Mitteilungen, xxv. (1889), p. 17. s Proc. Roy. Soc. Edin. xvii. (189o) p. 185. 7 Comptes rendus Acad. Sci. (Paris, 1890), vol. iii. p. 994. second great series of crust waves from north to south, giving rise by their interference to six great elevated masses (the continents), arranged in three groups, each consisting of a northern and a southern member separated by a minor depression. These elevated masses are divided from one another by similar great depressions. He says: " The surface of each of our great continental masses of land resembles that of a long and broad arch-like form, of which we see the simplest type in the New World. The Lap- surface of the North American arch is sagged down- worth's wards in the middle into a central depression which fold- lies between two long marginal plateaus, and these theory. plateaus are finally crowned by the wrinkled crests which form its two modern mountain systems. The surface of each of our ocean floors exactly resembles that of a continent turned upside down. Taking the Atlantic as our simplest type, we may say that the surface of an ocean basin resembles that of a mighty trough or syncline, buckled up more or less centrally in a medial ridge, which is bounded by two long and deep marginal hollows, in the cores of which still deeper grooves sink to the profoundest depths. This complementary relationship descends even to the minor features of the two. Where the great continental sag sinks below the ocean level, we have our gulfs and our Mediterraneans, seen in our type continent, as the Mexican Gulf and Hudson Bay. Where the central oceanic buckle attains the water-line we have our oceanic islands, seen in our type ocean, as St Helena and the Azores. Al-though the apparent crust-waves are neither equal in size nor symmetrical in form, this complementary relationship between them is always discernible. The broad Pacific depression seems to answer to the broad elevation of the Old World—the narrow trough of the Atlantic to the narrow continent of America.” The most thorough discussion of the great features of terrestrial relief in the light of their origin is that by Professor E. Suess,5 who points out that the plan of the earth is the result of Swess's two movements of the crust—one, subsidence over eory% wide areas, giving rise to oceanic depressions and leaving th the continents protuberant; the other, folding along comparatively narrow belts, giving rise to mountain ranges. This theory of crust blocks dropped by subsidence is opposed to Lapworth's theory of vast crust-folds, but geology is the science which has to decide between them. Geomorphology is concerned, however, in the suggestions which have been made as to the cause of the distribution of heap and hollow in the larger features of the crust. Elie de Beaumont, in his speculations on the relation between the direction of mountain ranges and their geological age and character, was feeling towards a comprehensive theory of the forms of crustal relief ; but his ideas were too geometrical, and his theory that the earth is a spheroil built up on a rhombic dodecahedron, the pentagonal faces of which determined the direction of mountain ranges, could not be proved,° The " tetrahedral theory " brought forward by Lowthian Green' , diametrically opposite to an ocean basin or great de- that the form of the earth is a spheroid based on a regular tetra, hedron, is more serviceable, because it accounts for three very ecm height ofGand-2300fL interesting facts of the terrestrial plan—(I) the antipodal f - - hfeaiLLeveZofCZobe(Land and Seap650it position of continents and ocean basins; (2) the tri- angular outline of the continents; and (3) the excess of sea in the southern hemisphere. Recent investigations have recalled attention to the work of Lowthian Green, but the question is still in the controversial stage.' The study of tidal strain in the earth's crust by Sir George _ y c P A T E A U Darwin has led that physicist to indicate the possibility of the triangular form and southerly direction of the continents being a result of the differential or tidal attraction of the sun and moon. More recently Professor 1 j~~ ( 1 A. E. H. Love has shown that the great features of the relief of the lithosphere may be expressed by spherical s 20 E' o't i0 55 t ~.•~ ~ ~ • ~' ~~~ 1 harmonics of the first, second and third degrees, and their formation related to gravitational action in a sphere of unequal density.' Sou In any case it is fuily recognized that the plan of the earth is so clear as to leave no doubt as to its being due to some general cause of crustal relief in a scheme of attractive simplicity. He If the level of the sea were to become coincident with the mean sees throughout all the chaos of irregular crust forms the level of the lithosphere, there would result one tri-radiate land-mass recurrence of a certain harmony, a succession of folds or of nearly uniform outline and one continuous sheet of water 00 5 Das Antlitz der Erde (4 vols., Leipzig, 1885, 1888, 1901). Translated under the editorship of E. de Margerie, with much additional matter, as La Face de la terre, vols. i. and ii. (Paris, 1897, 1900), and into English by Dr Hertha Sollas as The Face of the Earth, vols. i. and ii. (Oxford, 1904, 1906). 6 Elie de Beaumont, Notice sur les systemes de montagnes (3 vols., Paris, 1852). ' Vestiges of the Molten Globe (London, 1875). ° See J. W. Gregory, " The Plan of the Earth and its Causes,” Geog. Journal, xiii. (1899) p. 225; Lord Avebury, ibid. xv. (1900) p. 46; Marcel Bertrand, " Deformation tetraedrique de la terre et deplacement du pole," Comptes rendus Acad. Sci. (Paris, 1900), vol. cxxx. p 449; and A. de Lapparent, ibid. p. 614. s See A. E. H. Love, " Gravitational Stability of the Earth," Phil. Trans. ser. A. vol. ccvii. (1907) p. 171. and mean heights—the best results which have yet been obtained—led to the following conclusions.' The area of the dry land was taken as 28.3% of the surface of the globe, and that of the oceans as 71.7%. The mean height deduced for the land was 2300 ft. above sea-level, the mean depth Arens of of the sea 11,500 ft. below, while the position of mean-the crust sphere level comes out as 7500 ft. (125o fathoms) below acsordtd sea-level. From this it would appear that 43% of the to -i'agner' earth's surface was above and 57% below the mean level. It must be noted, however, that since 1895 the soundings of Nansen in the north polar area, of the " Valdivia,” " Belgica,” " Gauss " and " Scotia " in the Southern Ocean, and of various surveying ships in the North and South Pacific, have proved that the mean depth of the ocean is considerably greater than had been supposed, and mean-sphere level must therefore lie deeper than the calculations of 1895 show; possibly not far from the position deduced from the freer estimate of 1888. The whole of the available data were utilized by the prince of Monaco in 1905 in the preparation of a complete bathymetrical map of the oceans on a uniform scale, which must long remain the standard work for reference on ocean depths. By the device of a hypsographic curve co-ordinating the vertical relief and the areas of the earth's surface occupied by each zone of elevation, according to the system introduced by Supan,' Wagner showed his results graphically. This curve with the values reduced from metres to feet is re-produced below. Wagner subdivides the earth's surface, according to elevation, into the following five regions: Wagner's Divisions of the Earth's Crust: Name. Per cent of From To Surface. Depressed area . 3 Deepest. -16,400 feet. Oceanic plateau . 54 -16,400 feet. — 7,400 ,, Continental slope . 9 — 7,400 „ — 66o „ Continental plateau. 28 — 66o „ + 3,000 , Culminating area 6 + 3,300 „ Highest. The continental plateau might for purposes of detailed study be divided into the continental shelf from -66o ft. to sea-level, and lowlands from sea-level to +66o ft. (corresponding to sso•• n the mean level of the whole globe).3 Uplands reaching from 660 ft. to 2300 (the approximate mean level of the land), and highlands, from 2300 upwards, might also be distinguished. A striking fact in the configuration of the crust is that each continent, or elevated mass of the crust, is pression ; Arrangement of world ridges and hollows. waves which build up all the minor features.° One great series of crust waves from east to west is crossed by a South America, which is antipodal to eastern Asia. the only partial exception being in the case of southern Professor C. Lapworth has generalized the grand features which should be capable of detection. " Areal and mittlere Erhebung der Landflachen sowie der Erdkruste " in Gerland's Beitrage zur Geophysik, ii. (1895) p. 667. See also Nature, 54 (1896), p. 112. Peterrnanns Mitteilungen, xxxv. (1889) p. 19. ' The areas of the continental shelf and lowlands are approximately equal, and it is an interesting circumstance that, taken as a whole, the actual coast-line comes just midway on the most nearly level belt of the earth's surface, excepting the ocean floor. The con-figuration of the continental slope has been treated in detail by Nansen in Scientific Results of Norwegian North Polar Expedition, vol. iv. (1904), where full references to the literature of the subject will be found.. British Association Report (Edinburgh, 1892), p. 699. 632 broken by few islands. The actual position of sea-level lies so near the summit of the crust-heap that the varied relief of the upper portion leads to the formation of a complicated coast-The con- line and a great number of detached portions of land. tinents. The hydrosphere is, in fact, continuous, and the land is all in insular masses: the largest is the Old World of Europe, Asia and Africa ; the next in size, America ; the third, possibly, Antarctica; the fourth, Australia; the fifth, Greenland. After this there is a considerable gap before New Guinea, Borneo, Madagascar, Sumatra and the vast multitude of smaller islands descending in size by regular gradations to mere rocks. The contrast between island and mainland was natural enough in the days before the discovery of Australia, and the mainland of the Old World was traditionally divided into three continents. These " continents," " parts of the earth," or " quarters of the globe," proved to be convenient divisions; America was added as a fourth, and subsequently divided into two, while Australia on its discovery was classed sometimes as a new continent, sometimes merely as an island, some-times compromisingly as an island-continent, according to individual opinion. The discovery of the insularity of Greenland might again give rise to the argument as to the distinction between island and continent. Although the name of continent was not applied to large portions of land for any physical reasons, it so happens that there is a certain physical similarity or homology between them which is not shared by the smaller islands or peninsulas. The typical continental form is triangular as regards its sea-level outline. The relief of the surface typically includes a central plain, Homology sometimes dipping below sea-level, bounded by lateral of con- highlands or mountain ranges, loftier on one side than tinenta. on the other, the higher enclosing a plateau shut in by mountains. South America and North America follow this type most closely; Eurasia (the land mass of Europe and Asia) comes next, while Africa and Australia are farther removed from the type, and the structure of Antarctica and Greenland is unknown. If the continuous, unbroken, horizontal extent of land in a continent is termed its trunk,' and the portions cut up by inlets or channels of the sea into islands and peninsulas the limbs, it is possible to compare the continents in an instructive manner. The following table is from the statistics of Professor H. Wagner? his metric measurements being transposed into British units: Comparison of the Continents. The usual classification of islands is into continental and oceanic. The former class includes all those which rise from the continental islands. shelf, or show evidence in the character of their rocks of having at one time been continuous with a neighbouring continent. The latter rise abruptly from the oceanic abysses. Oceanic islands are divided according to their geological character into volcanic islands and those of organic origin, including coral islands. More elaborate subdivisions according to structure, origin and position have been proposed.' In some cases a piece of land is only an island at high water, and by imperceptible gradation the form passes into a peninsula. The typical peninsula is connected with the mainland by a relatively narrow isthmus; the name is, however, ex-tended to any limb projecting from the trunk of the mainland, even when, as in the Indian peninsula, it is connected by its widest part. Small peninsulas are known as promontories or headlands, and the extremity as a cape. The opposite form, an inlet of the sea, is known when wide as a gulf, bay or bight, according to size and degree of inflection, or as a fjord or ria when long and narrow. It is convenient to employ a specific name for a projection of a coast-line less pronounced than a peninsula, and for an inlet less pronounced than a bay or bight; outcurve and incurve may serve the turn. The varieties of coast-lines were reduced to an. exact classification by Richthofen, who grouped them according to . the height and slope of the land into cliff-coasts (Steilkiisten)- narrow beach coasts with cliffs, wide beach coasts with cliffs, and Rumpf, in German, the language in which this distinction was first made. 2 Lehrbuch der Geographie (Hanover and Leipzig, 1900), Bd. i. S. 245, 249. ' See, for example, F. G. Hahn's Insel-Studien (Leipzig, 1883).[PRINCIPLES low coasts, subdividing each group according as the coast-line runs parallel to or crosses the line of strike of the mountains; or is not related to mountain structure. A further subdivision depends on the character of the inter-relation of land and sea along the shore producing such types as a fjord-coast, ria-coast or lagoon-coast. This extremely elaborate subdivision may be reduced, as Wagner points out, to three types-the continental coast where the sea comes up to the solid rock-material of the land; the marine coast, which is formed entirely of soft material sorted out by the sea; and the composite coast, in which both forms are combined. On large-scale maps it is necessary to show two coast-lines, one for the highest, the other for the lowest tide; but in small-scale maps a single line is usually wider than is required to Coast- represent the whole breadth of the inter-tidal zone. !Ines. The measurement of a coast-line is difficult, because the length will necessarily be greater when measured on a large-scale map where minute irregularities can be taken into account. It is usual to distinguish between the general coast-line measured from point to point of the headlands disregarding the smaller bays, and the detailed coast-line which takes account of every inflection shown by the map employed, and follows up river entrances to the point where tidal action ceases. The ratio between these two coast-lines represents the " coastal development " of any region. While the forms of the sea-bed are not yet sufficiently well known to admit of exact classification, they are recognized to be as a rule distinct from the forms of the land, and the importance Submarine of using a distinctive terminology is felt. Efforts have forms. been made to arrive at a definite international agreement on this subject, and certain terms suggested by a committee were adopted by the Eighth International Geographical Congress at New York in 1904.' The forms of the ocean floor include the " shelf," or shallow sea margin, the " depression," a general term applied to all submarine hollows, and the " elevation." A depression when of great extent is termed a " basin," when it is of a more or less round form with approximatelyequal diameters, a " trough " when it is wide and elongated with gently sloping borders, and a " trench " when narrow and elongated with steeply sloping borders, one of which rises higher than the other. The extension of a trough or basin penetrating the land or an elevation is termed an " embayment ' when wide, and a " gully " when long and narrow; and the deepest part of a depression is termed a " deep." A depression of small extent when steep-sided is termed a " caldron," and a long narrow depression crossing a part of the continental border is termed a " furrow." An elevation of great extent which rises at a very gentle angle from a surrounding, depression is termed a " rise," one which is relatively narrow and steep-sided a " ridge," and one which is approximately equal in length and breadth but steep-sided a " plateau," whether it springs direct from a depression or from a rise. An elevation of small extent is distinguished as a dome " when it is more than too fathoms from the surface, a " bank " when it is nearer the surface than loo fathoms but deeper than 6 fathoms, and a " shoal " when it comes within 6 fathoms of the surface and so becomes a serious danger to ship-ping. The highest point of an elevation is termed a ' height," if it does not form an island or one of the minor forms. The forms of the dry land are of infinite variety, and have been studied in great detail.' From the descriptive or topographical point of view, geometrical form alone should be con- Land sidered; but the origin and geological structure of land forms must in many cases be taken into account forms. when dealing with the function they exercise in the control of mobile distributions. The geographers who have hitherto given most attention to the forms of the land have been trained as geologists, and consequently there is a general tendency to make origin or structure the basis of classification rather than form alone. The fundamental form-elements may be reduced to the six proposed by Professor Penck as the basis of his double system of classification by form and origin.' These may be looked Tbestx upon as being all derived by various modifications or lemen etary arrangements of the single form-unit, the slope or inclined landforms. plane surface. No one form occurs alone, but always grouped together with others in various ways to make up districts, regions and lands of distinctive characters. The form-elements are: ' See Geographical Journal, xxii. (1903) pp. 191-194. ' The most important works on the classification of land forms are F. von Richthofen, Fiihrer fur Forschungsreisende (Berlin, 1886); G. de la Noe and E. de Margerie, Les Formes du terrain (Paris, 1888) ; and above all A. Penck, Morphologie der Erdoberfldche (2 vols., Stuttgart, 1894). Compare also A. de Lapparent, Lecons de geographie physique (2nd ed., Paris, 1898), and W. M. Davis, Physical Geography (Boston, 1899). ' Geomorphologie als genetische Wissenschaft," in Report of Sixth International Geog. Congress (London, 1895), p. 735 (English Abstract, p. 748). Coasts. Area Mean Area Area Area Area Area total height, trunk, enin- i,,lands, limbs, limbs, mil. feet. mil. sulas, mil. mil. per sq. m. sq. m. mil. sq. m. sq. m. cent. sq. m. Old World . 35.8 2360 New World 16.2 2230 Eurasia 20.85 262o 15.42 4.09 1.34 5.43 26 Africa 11.46 2130 II.22 0.24 0.24 2•I North America 9.26 2300 6.92 0.78 1.56 2.34 25 South America 6.84 197o 6.76 0.02 0.06 0.08 1.1 Australia 3'43 1310 2.77 0.16 0.50 0.66 19 Asia 17.02 3120 12.93 3.05 1'04 4'09 24 Europe 3.83 980 2.49 1.04 0.30 1'34 35 1. The plain or gently inclined uniform surface. 2. The scarp or steeply inclined slope; this is necessarily of small extent except in the direction of its length. 3. The valley, composed of two lateral parallel slopes inclined towards a narrow strip of plain at a lower level which itself slopes downwards in the direction of its length. Many varieties of this fundamental form may be distinguished. 4. The mount, composed of a surface falling away on every side from a particular place. This place may either be a point, as in a volcanic cone, or a line, as in a mountain range or ridge of hills. 5. The hollow or form produced by a land surface sloping inwards from all sides to a particular lowest place, the converse of a mount. 6. The cavern or space entirely surrounded by a land surface. These forms never occur scattered haphazard over a region, but always in an orderly subordination depending on their mode veotogy of origin. The dominant forms result from crustal aeotand movements, the subsidiary from secondary reactions forms during the action of the primitive forms on mobile distri- butions. The geological structure and the mineral composition of the rocks are often the chief causes determining the character of the land forms of a region. Thus the scenery of a lime-stone country depends on the solubility and permeability of the rocks, leading to the typical Karst-formations of caverns, swallow-holes and underground stream courses, with the contingent phenomena of dry valleys and natural bridges. A sandy beach or desert owes its character to the mobility of its constituent sand-grains, which are readily drifted and piled up in the form of dunes. A region where volcanic activity has led to the embedding of dykes or bosses of hard rock amongst softer strata produces a plain broken by abrupt and isolated eminences.' It would be impracticable to go fully into the varieties of each specific form; but, partly as an example of modern geographical Glasslike• classification, partly because of the exceptional importtion of ance of mountains amongst the features of the land, one mountains. exception may be made. The classification of mountains into types has usually had regard rather to geological structure than to external form, so that some geologists would even apply the name of a mountain range to a region not distinguished by relief from the rest of the country if it bear geological evidence of having once been a true range. A mountain may be described (it cannot be defined) as an elevated region of irregular surface rising comparatively abruptly from lower ground. The actual elevation of a summit above sea-level does not necessarily affect its mountainous character; a gentle eminence, for instance, rising a few hundred feet above a tableland, even if at an elevation of say 15,000 ft., could only be called a hill.2 But it may be said that any abrupt slope of 2000 ft. or more in vertical height may justly be called a mountain, while abrupt slopes of lesser height may be called hills. Existing classifications, however, do not take account of any difference in kind between mountain and hills, although it is common in the German language to speak of Hugel-land, Mittelgebirge and Hochgebirge with a definite significance. The simple classification employed by Professor James Geikie 4 into mountains of accumulation, mountains of elevation and mountains of circumdenudation, is not considered sufficiently thorough by German geographers, who, following Richthofen, generally adopt a classification dependent on six primary divisions, each of which is subdivided. The terms employed, especially for the sub-divisions, cannot be easily translated into other languages, and the English equivalents in the following table are only put forward tentatively RICHTHOFEN'S CLASSIFICATION OF MOUNTAINS 4 I. Tektonische Gebirge—Tectonic mountains. (a) Bruchgebirge oder Schollengebirge—Block mountains. 1. Einseitige Schollengebirge oder Schollenrandgebirge—Scarp or tilted block mountains. (i.) Tafelscholle—Table blocks. (ii.) Abrasionsscholle—Abraded blocks. (iii.) Transgressionsscholle—Blocks of unconformable strata. 2. Flexurgebirge—Flexure mountains. 3. Horstgebirge—Symmetrical block mountains. (b) Faltungsgebirge—Fold mountains. 1. Homoomorphe Faltungsgebirge—Homomorphic fold mountains. 2. Heteromorphe Faltungsgebirge—Heteromorphic fold mountains. On this subject see J. Geikie, Earth Sculpture (London, 1898) ; J. E. Marr, The Scientific Study of Scenery (London, i9oo); Sir A. Geikie, The Scenery and Geology of Scotland (London, 2nd ed., 1887) ; Lord Avebury (Sir J. Lubbock), The Scenery of Switzerland (London, 1896) and The Scenery of England (London, 1902). 2 Some geographers distinguish a mountain from a hill by origin; thus Professor Seeley says " a mountain implies elevation and a hill implies denudation, but the external forms of both are often identical." Report VI. Int. Geog. Congress (London, 1895), p. 751. " Mountains," in Scot. Geog. Mag. ii. (1896) p. 145. 4 Fuhser fir Forschungsreisende, pp. 652-685.II. Rumpfgebirge oder Abrasionsgebirge—Trunk or abraded mountains. IV. Aufschiittungsgebirge—Mountains of accumulation. V. Flachboden—Plateaux. (a) Abrasionsplatten—Abraded plateaux. (b) Marines Flachland—Plain of marine erosion. (c) Schichtungstafelland—Horizontally stratified tableland. (d) Ubergusstafelland—Lava plain. (e) Stromflachland—River plain. (f) FlachbOden der atmosphdrischen Aufschuttung—Plains of aeolian formation. VI. Erosionsgebirge—Mountains of erosion. From the morphological point of view it is more important to distinguish the associations of forms, such as the mountain mass or group of mountains radiating from a centre, with the valleys furrowing their flanks spreading towards every forms. direction ; the mountain chain or line of heights, forming a long narrow ridge or series of ridges separated by parallel valleys; the dissected plateau or highland, divided into mountains of circumdenudation by a system of deeply-cut valleys; and the isolated peak, usually a volcanic cone or a hard rock mass left projecting after the softer strata which embedded it have been worn away (Monadnock of Professor Davis). The geographical distribution of mountains is intimately associated with the great structural lines of the continents of which they form the culminating region. Lofty lines of fold mountains Distribuform the " backbones " of North America in the Rocky tton of Mountains and the west coast systems, of South America mountains. in the Cordillera of the Andes, of Europe in the Pyrenees, Alps, Carpathians and Caucasus, and of Asia in the mountains of Asia Minor, converging on the Pamirs and diverging thence in the Himalaya and the vast mountain systems of central and eastern Asia. The remarkable line of volcanoes around the whole coast of the Pacific and along the margin of the Caribbean and Mediterranean seas is one of the most conspicuous features of the globe. If land forms may be compared to organs, the part they serve in the economy of the earth may, without straining the term, be characterized as functions. The first and simplest Functions function of the land surface is that of guiding loose offend material to a lower level. The downward pull of gravity forms. suffices to bring about the fall of such material, but the path it will follow and the distance it will travel before coming to rest depend upon the land form. The loose material may, and in an arid region does, consist only of portions of the higher parts of the surface detached by the expansion and waste. contraction produced by heating and cooling due to radiation. Such broken material rolling down a uniform scarp would tend to reduce its steepness by the loss of material in the upper part and by the accumulation of a mound or scree against the lower part of the slope. But where the side is not a uniform scarp, but made up of a series of ridges and valleys, the tendency will be to distribute the detritus in an irregular manner, directing it away from one place and collecting it in great masses in another, so that in time the land form assumes a new appearance. Snow accumulating on the higher portions of the land, when compacted into ice and caused to flow downwards by gravity, gives rise, on account of its more coherent character, to continuous Qtaakrs glaciers, which mould themselves to the slopes down which they are guided, different ice-streams converging to send forward a greater volume. Gradually coming to occupy definite beds, which are deepened and polished by the friction, they impress a characteristic appearance on the land, which guides them as they traverse it, and, although the ice melts at lower levels, vast quantities of clay and broken stones are brought down and deposited in terminal moraines where the glacier ends. Rain is by far the most important of the inorganic mobile distributions upon which land forms exercise their function of guidance and control. The precipitation of rain from the aqueous Rata. vapour of the atmosphere is caused in part by vertical movements of the atmosphere involving heat changes and apparently independent of the surface upon which precipitation occurs; but in greater part it is dictated by the form and altitude of the land surface and the direction of the prevailing winds, which itself is largely influenced by the land. It is on the windward faces of the highest ground, or just beyond the summit of less dominant heights upon the leeward side, that most rain falls, and all that does not evaporate or percolate into the ground is conducted back to the sea by a route which depends only on the form of the land. More mobile and more searching than ice or rock rubbish, the trickling drops are guided by the deepest lines of the hillside in their incipient flow, and as these lines converge, the stream, gaining strength, proceeds in River its torrential course to carve its channel deeper and en- systems. trench itself in permanent occupation. Thus the stream- bed, from which at first the water might be blown away into a new channel by a gale of wind, ultimately grows to be the strongest line of the landscape. As the main valley deepens, the tributary stream-beds are deepened also, and gradually cut their way headwards, enlarging the area whence they draw their supplies. Thus new land forms are created—valleys of curious complexity, for example— by the " capture " and diversion of the water of one river by another, leading to a change of watershed.' The minor tributaries become more numerous and more constant, until the system of torrents has impressed its own individuality on the mountain side. As the river leaves the mountain, ever growing by the accession of tributaries, it ceases, save in flood time, to be a formidable instrument of destruction; the gentler slope of the land surface gives to it only power sufficient to transport small stones, gravel, sand and ultimately mud. Its valley banks are cut back by the erosion of minor tributaries, or by rain-wash if the climate be moist, or left steep and sharp while the river deepens its bed if the climate be arid. The outline of the curve of a valley's sides ultimately depends on the angle of repose of the detritus which covers them, if there has been no subsequent change, such as the passage of a glacier along the valley, which tends to destroy the regularity of the cross-section. The slope of the river bed diminishes until the plain compels the river to move slowly, swinging in meanders proportioned to its size, and gradually, controlled by the flattening land, ceasing to transport material, but raising its banks and silting up its bed by the dropped sediment, until, split up and shoaled, its distributaries struggle across its delta to the sea. This is the typical river of which there are infinite varieties, yet every variety would, if time were given, and the land remained unchanged in level relatively to the sea, Adjust.. ultimately approach to the type. Movements of the land meat of either of subsidence or elevation, changes in the land by rivers to the action of erosion in cutting back an escarpment or land. cutting through a col, changes in climate by affecting the rainfall and the volume of water, all tend to throw the river valley out of harmony with the actual condition of its stream. There is nothing more striking in geography than the perfection of the adjustment of a great river system to its valleys when the land has remained stable for a very lengthened period. Before full adjustment has been attained the river bed may be broken in places by waterfalls or interrupted by lakes; after adjustment the bed assumes a permanent outline, the slope diminishing more and more gradually, without a break in its symmetrical descent. Excellent examples of the indecisive drainage of a new land surface, on which the river system has not had time to impress itself, are to be seen in northern Canada and in Finland, where rivers are separated by scarcely perceptible divides, and the numerous lakes frequently belong to more than one river system. The action of rivers on the land is so important that it has been made the basis of a system of physical geography by Professor W. M. Davis, who classifies land surfaces in terms of The the three factors—structure, process and time.' Of grip. these time, during which the process is acting on the cycle structure, is the most important. A land may thus be characterized by its position in the " geographical cycle, ' or cycle of erosion, as young, mature or old, the last term being reached when the base-level of erosion is attained, and the land, however varied its relief may have been in youth or maturity, is reduced to a nearly uniform surface or peneplain. By a re-elevation of a peneplain the rivers of an old land surface may be restored to youthful activity, and resume their shaping action, deepening the old valleys and initiating new ones, starting afresh the whole course of the geographical cycle. It is, however, not the action of the running water on the land, but the function exercised by the land on the running water, that is considered here to be the special province of geography. At every stage of the geographical cycle the land forms, as they exist at that stage, are concerned in guiding the condensation and flow of water in certain definite ways. Thus, for example, in a mountain range at right angles to a prevailing sea-wind, it is. the land forms which determine that one side of the range shall be richly watered and deeply dissected by a complete system of valleys, while the other side is dry, indefinite in its valley systems, and sends none of its scanty drainage to the sea. The action of rain, ice and rivers conspires with the movement of land waste to strip the layer of soil from steep slopes as 'rapidly as it forms, and to cause it to accumulate on the fiat valley bottoms, on the graceful flattened cones of alluvial fans at the outlet of the gorges of tributaries, or in the smoothly-spread surface of alluvial plains. The whole question of the regime of rivers and lakes is sometimes treated under the name hydrography, a name used by some writers in the sense of marine surveying, and by others as synonymous with oceanography. For the study of rivers alone the name potamology has been suggested by Penck, and the subject being of much practical importance has received a good deal of attention.' The study of lakes has also been specialized under,the name of ' See, for a summary of river-action, A. Phillipson, Studien fiber Wasserscheiden (Leipzig, 1886) ; also I.C. Russell, River Development, (London, 1898) (published as The Rivers of North America, New York, 1898). ' W. M. Davis, " The Geographical Cycle," Geog. Journ. xiv. (1899) P. 484. ' A. Penck, " Potamology as a Branch of Physical Geography," Geog. Journ. x. (1897) p. 619. ' See, for instance, E. Wisotzki, Hauptfluss and Nebenfluss (Stettin, 1889). For practical studies see official reports on the Mississippi, Rhine, Seine, Elbe and other great rivers.limnology (see LAKE).' The existence of lakes in hollows of the land depends upon the balance between precipitation and evaporation. A stream flowing into a hollow will tend to fill it up, and ,ekes and the water will begin to escape as soon as its level rises high internal enough to reach the lowest part of the rim. In the case drainage. of a large hollow in a very dry climate the rate of evaporation may be sufficient to prevent the water from ever rising to the lip, so that there is no outflow to the sea, and a basin of internal drainage is the result. This is the case, for instance, in the Caspian sea, the Aral and Balkhash lakes, the Tarim basin, the Sahara, inner Australia, the great basin of the United States and the Titicaca basin. These basins of internal drainage are calculated to amount to 22 % of the land surface. The percentages of the land surface draining to the different oceans are approximately—Atlantic; 34'3 %; Arctic sea, 16.5 %; Pacific, 14.4 %; Indian Ocean 12.8 %.6 The parts of a river system have not been so clearly defined as is desirable, hence the exaggerated importance popularly attached to " the source " of a river. A well-developed river System Teerrmigo~ has in fact many equally important and widely-separated iii sources, the most distant from the mouth, the highest, rover or even that of largest initial volume not being neces- Systems. sarily of greater geographical interest than the rest. The whole of the land which directs drainage towards one river is known as its basin, catchment area or drainage area—sometimes, by an incorrect expression, as its valley or even its watershed. The boundary line between one drainage area and ethers is rightly termed the watershed, but on account of the ambiguity which has been tolerated it is better to call it water-parting or, as in America, divide. The only other important term which requires to be noted here is talweg, a word introduced from the German into French and English, and meaning the deepest line along the valley; which is necessarily occupied by a stream unless the valley is dry. The functions of land forms extend beyond the control of the circulation of the atmosphere, the hydrosphere and the water which is continually being interchanged between them; they are exercised with increased effect in the higher departments of biogeography and anthropogeography. The sum of the organic life on the globe is termed by some geographers the biosphere, and it has been estimated that the whole mass of living substance in existence at one time would cover the surface of the earth to a depth of one-fifth of an inch.' The distribution of living organisms is a graph-Y. complex problem, a function of many factors, several of which are yet but little known. They include the biological nature of the organism and its physical environment, the latter involving conditions in which geographical elements, direct or indirect, preponderate. The direct geographical elements are the arrangement of land and sea (continents and islands standing in sharp contrast) and the vertical relief of the globe, which interposes barriers of a less absolute kind between portions of the same land area or oceanic depression. The indirect geographical elements, which, as a rule, act with and intensify the direct, are mainly climatic; the prevailing winds, rainfall, mean and extreme temperatures of every locality depending on the arrangement of land and sea and of land forms. Climate thus guided affects the weathering of rocks, and so determines the kind and arrangement of soil. Different species of organisms come to perfection in different climates; and it may be stated as a general rule that a species, whether of plant or animal, once established at one point, would spread over the whole zone of the climate congenial to it unless some barrier were interposed to its progress. In the case of land and fresh-water organisms the sea is the chief barrier; in the case of marine organisms, the land. Differences in land forms do not exert great influence on the distribution of living creatures directly, but indirectly such land forms as mountain ranges and internal drainage basins are very potent through their action on soil and climate. A snow-capped mountain ridge or an arid desert forms a barrier between different forms of life which is often more effective than an equal breadth of sea. In this way the surface of the land is divided into numerous natural regions, the flora and fauna of each of which include some distinctive species not shared by the others. The distribution of life is discussed in the various articles in this Encyclopaedia dealing with biological, botanical and zoological subjects.' s F. A. Forel, Handbuch der Seenkunde: allgemeine Limnologie (Stuttgart, 1901) ; F. A. Forel, " La Limnologie, branche de la geographic," Report VI. Int. Geog. Congress (London, 1895), p. 593; also Le Leman (2 vols., Lausanne, 1892, 1894) ; H. Lullies. " Studien uber Seen," Jubilaumsschrift der Albertus- Universit¢t (Konigsbetg, 1894) ; and G. R. Credner, " Die Reliktenseen," Petermann Mitteilucgen, Erganzungshefte 86 and 89 (Gotha. 1887, 1888). J. Murray, " Drai+e ge Areas of the Continents," Scot. Geog. Mae. ii. (1886) p. 548. ' Wagner, Lehrbuch der Geographic (1900), i. 586. ' For details, see A. R. Wallace, Geographical Distribution of Animals and Island Life; A. Heilprin, Geographical and Geological Distribution of Animals (1887) ; O. Drude, Handbuch der Pflanze3tgeographie; A. Engler, Entwickelungsgeschichte der Pflanzenwelt; also Beddard, Zoogeography (Cambridge, 1895); andSciater, The Geography of Mammals (London, 1899). The classification of the land surface into areas inhabited by distinctive groups of plants has been attempted by many phyto-Florat geographers, but without resulting in any scheme of general acceptance. The simplest classification is perhaps zones. that of Drude according to climatic zones, subdivided according to continents. This takes account of—(1) the Arctic-Alpine zone, including all the vegetation of the region bordering on perpetual snow; (2) the Boreal zone, including the temperate lands of North America, Europe and Asia, all of which are substantially alike in botanical character; (3) the Tropical zone, divided sharply into (a) the tropical zone of the New World, and (b) the tropical acne of the Oid World, the forms of which differ in a significant degree; (4) the Austral zone, comprising all continental land south of the equator, and sharply divided into three regions the floras of which are strikingly distinct—(a) South American, (b) South African and (c) Australian; (5) the Oceanic, comprising all oceanic islands, the flora of which consists exclusively of forms whose seeds could be drifted undestroyed by ocean currents or carried by birds. To these might be added the antarctic, which is still very imperfectly kno*n. Many subdivisions and transitional zones have been suggested by different authors. From the point of view of the economy of the globe this classification by species is perhaps less important than that by mode ' of life and physiological character in accordance with vegetation environment. The following are the chief areas of arras' vegetational activity usually recognized: (1) The ice-deserts of the arctic and antarctic and the highest mountain regions, where there is no vegetation except the lowest forms, like that which causes red snow." (2) The tundra or region of intensely cold winters, forbidding tree-growth, where mosses and lichens cover most of the ground when unfrozen, and shrubs occur of species which in other conditions are trees, here stunted to the height of a few inches. A similar zone surrounds the permanent snow on lofty mountains in all latitudes. The tundra passes by imperceptible gradations into the moor, bog and heath of warmer climates. (3) The temperate forests of evergreen or deciduous trees, according to circumstances, which occupy those parts of both temperate zones where rainfall and sunlight are both abundant. (4j The grassy steppes or prairies where the rainfall is diminished and temperatures are extreme, and grass is the prevailing form of vegetation. These pass imperceptibly into—(5) the arid desert, where rainfall is at a minimum, and the only plants are those modified to subsist with the smallest supply of water. (6) The tropical forest, which represents the maximum of plant luxuriance, stimulated by the heaviest rainfall, greatest heat and strongest light. These divisions merge one into the other, and admit of almost indefinite subdivision, while they are subject to great modifications by human interference in clearing and cultivating. Plants exhibit the control-ling power of environment to a high degree, and thus vegetation is usually in close adjustment to the bolder geographical features of a region. The divisions of the earth into taunal regions by Dr P. L. Sclater have been found to hold good for a large number of groups of animals as different in their mode of life as birds and mammals, Faunal almsl. and they may thus be accepted as based on nature. realms. They are six in number: (1) Palaearctic, including Europe, Asia north of the Himalaya, and Africa north of the Sahara; (2) Ethiopian, consisting of Africa south of the Atlas range, and Madagascar; (3) Oriental, including India, Indo-China and the Malay Archipelago north of Wallace's line, which runs between Bali and Lombok; (4) Australian, including Australia, New Zealand, New Guinea and Polynesia; (5) Nearctic or North America, north of Mexico; and (6) Neotropical or South America. Each of these divisions is the home of a special fauna, many species of which are confined to it alone; in the Australian region, indeed, practically the whole fauna is peculiar and distinctive, suggesting a prolonged period of ,complete biological isolation. In some cases, such as the Ethiopian and Neotropical and the Palaearctic and Nearctic regions, the faunas, although distinct, are related, several forms on opposite sides of the Atlantic being analogous, e.g. the lion and puma, ostrich and rhea. Where two of the faunal realms meet there is usually, though not always, a mixing of faunas. These facts have led some naturalists to include the Palaearctic and Nearctic regions in one, termed Holarciic, and to suggest transitional regions, such as the Sonoran, between North and South America, and the Mediterranean, between Europe and Africa, or to create sub-regions, such as Madagascar and New Zealand. Oceanic islands have, as a rule, distinctive faunas and floras which resemble, but are not identical with, those of other islands in similar positions. The study of the evolution of, faunas and the comparison of the faunas of distant regions have furnished a trustworthy Biological instrument of pre-historic geographical research, which distribu- enables earlier geographical relations of land and sea to tion as be traced out, and the approximate period, or at least the an"' chronological order of the larger changes, to be estimated. o/goo- In this way, for example, it has been suggested that a graphical land, " Lemuria," once connected Madagascar with the research. Malay Archipelago, and that a northern extension' of the antarctic land once united the three southern continents. The distribution of fossils frequently makes it possible to map outapproximately the general features of land and sea in long-past geological periods, and so to enable the history of crustal relief to be traced.' While the tendency is for the living forms to come into harmony with their environment and to approach the state of equilibrium by successive adjustments if the environment should Reaction o! happen to change, it is to be observed that the action of organisms themselves often tends to change their organisms environment. Corals and other quick-growing cal- onenvtron careous marine organisms are the most powerful in this 'Bent. respect by creating new land in the ocean. Vegetation of all sorts acts in a similar way, either in forming soil and assisting in breaking up rocks, in filling up shallow lakes, and even, like the man-grove, in reclaiming wide stretches of land from the sea. Plant life, utilizing solar light to combine the inorganic elements of water, soil and air into living substance, is the basis of all animal life. This is not by the supply of food alone, but also by the withdrawal of carbonic acid from the atmosphere, by which vegetation maintains the composition of the air in a state fit for the support of animal life. Man in the primitive stages of culture is scarcely to be distinguished from other animals as regards his subjection to environment, but in the higher grades of culture the conditions of control and reaction become much more complicated, and the department of anthropogeography is devoted to their consideration. The first requisites of all human beings are food and protection, in their search for which men are brought into intimate relations with the forms and productions of the earth's surface. Anthropo-The degree of dependence of any people upon environment varies inversely as the degree of culture or civiliza- geography. tion, which for this purpose may perhaps be defined as the power of an individual to exercise control over the individual and over the environment for the benefit of the community. The development of culture is to a certain extent a question of races and although forming one species, the varieties of man differ in almost imperceptible gradations with a complexity defying classification (see ANTHROPOLOGY). Professor Keane groups man round four leading types, which may be named the black, yellow, red and white, or the Ethiopic, Mongolic, American and Caucasic. Each may be subdivided, though not with great exactness, into smaller groups, either according to physical characteristics, of which the form of the head is most important, or according to language. The black type is found only in tropical or sub-tropical countries, and is usually in a primitive condition of culture, unless educated by contact with people of the white type. They follow Types of the most primitive forms of religion (mainly fetishism), man. live on products of the woods or of the chase, with the minimum of work, and have only a loose political organization. The red type is peculiar to America, inhabiting every climate from polar to equatorial, and containing representatives of many stages of culture which had apparently developed without the aid or interference of people of any other race until the close of the 15th century. The yellow type rs capable of a higher culture, cherishes higher religious beliefs, and inhabits as a rule the temperate zone, although extending to the tropics on one side and to the arctic regions on the other. The white type, originating in the north temperate zone, has spread over the whole world. They have attained the highest culture, profess the purest forms of mono-theistic religion, and have brought all the people of the black type and many of those of the yellow under their domination. The contrast between the yellow and white types has been softened by the remarkable development of the Japanese following the assimilation of western methods. The actual number of human inhabitants in the world has been calculated as follows: By Continents., Asia . 875,000,000 Europe . 392,000,000 Africa . . . 170,000,000 America . 143,000,000 Australia and 7,000,000 Polynesia Total 1,587,000,000 In round numbers the population of the world is about 1,600,000,000, and, according to an estimate by Ravenstein,4 the maximum population which it will be possible for the earth to maintain is 6000 millions, a number which, if the average rate of increase in 1891 continues, would he reached within 200 years. While highly civilized communities are able to evade many of the restrictions of environment, to otrercome the barriers to inter-communication interposed by land or sea, to counteract the adverse 1 See particularly A. de Lapparent, Traits de geologic (4th ed., Paris, 1900). 2 Estimate for 1900. H. Wagner, Lehrbuch der Geographie, i. p. 658. 3 Estimate for year not stated. A. H. Keane in International Geography, p. 108. 4 In Proc. R.G.S. xiii. (1891) p. 27. By Race? White (Caucasic) 770,000,000 Yellow (Mong) . 540,000,000 Black (Ethiopic) . 175,000,000 Red (American) . 22,000,000 Total . 1,507,000,000 influence of climate, and by the development of trade even to inhabit countries which cannot yield a food-supply, the mass of mankind is still completely under the control of those conditions which in the past determined the distribution and the mode of life of the whole human race. In tropical forests primitive tribes depend on the collection of wild fruits, and in a minor degree on the chase of wild animals, for Influence their food. Clothing is unnecessary; hence there is o n- little occasion for exercising the mental faculties beyond meat on the sense of perception to avoid enemies, or the in- men. ventive arts beyond what is required for the simplest weapons and the most primitive fortifications. When the pursuit of game becomes the chief occupation of a people there is of necessity a higher development of courage, skill, powers of observation and invention; and these qualities are still further enhanced in predatory tribes who take by force the food, clothing and other property prepared or collected by a feebler people. The fruit-eating savage cannot stray beyond his woods which bound his life as the water bounds that of a fish; the hunter is free to live on the margin of forests or in open country, while the robber or warrior from some natural stronghold of the mountains sweeps over the adjacent plains and carries his raids into distant lands. Wide grassy steppes lead to the organization of the people as nomads whose wealth consists in flocks and herds, and their dwellings are tents. The nomad not only domesticates and turns to his own use the gentler and more powerful animals, such as sheep, cattle, horses, camels, but even turns some predatory creatures, like the dog, into a means of defending their natural prey. They hunt the beasts of prey destructive to their flocks, and form armed bands for protection against marauders or for purposes of aggression on weaker sedentary neighbours. On the fertile low grounds along the margins of rivers or in clearings of forests, agricultural communities naturally take their rise, dwelling in villages and cultivating the wild grains, which by careful nurture and selection have been turned into rich cereals. The agriculturist as a rule is rooted to the soil. The land he tills he holds, and acquires a closer connexion with a particular patch of ground than either the hunter or the herds-man. In the temperate zone, where the seasons are sharply contrasted, but follow each other with regularity, foresight and self-denial were fostered, beca.use if men did not exercise these qualities seed-time or harvest might pass into lost opportunities and the tribes would suffer. The more extreme climates of arid regions on the margins of the tropics, by the unpredictable succession of droughts and floods, confound the prevision of uninstructed people, and make prudence and industry qualities too uncertain in their results to be worth cultivating. Thus the civilization of agricultural peoples of the temperate zone grew rapidly, yet in each community a special type arose adapted to the soil, the crop and the climate. On the sea-shore fishing naturally became a means of livelihood, and dwellers by the sea, in virtue of the dangers to which they are exposed from storm and unseaworthy craft, are stimulated to a higher degree of foresight, quicker observation, prompter decision and more energetic action in emergencies than those who live inland. The building and handling of vessels also, and the utilization of such uncontrollable powers of nature as wind and tide, helped forward mechanical invention. To every type of coast there may be related a special type of occupation and even of character; the deep and gloomy fjord, backed by almost impassable mountains, bred bold mariners *hose only outlet for enterprise was seawards towards other lands—the viks created the vikings. On the gently sloping margin of the estuary of a great river a view of tranquil inland life was equally presented to the shore-dweller, and the ocean did not present the only prospect of a career. Finally the mountain valley, with its patches of cultivable soil on the alluvial fans of tributary torrents, its narrow pastures on the uplands only left clear of snow in summer, its intensified extremes of climates and its isolation, almost equal to that of an island, has in all countries produced a special type of brave and hardy people, whose utmost effort may bring them comfort, but not wealth, by honest toil, who know little of the outer world, and to whom the natural outlet for ambition is marauding on the fertile plains. The highlander and viking, products of the valleys raised high amid the mountains or half-drowned in the sea, are everywhere of kindred spirit. It is in some such manner as these that the natural conditions of regions, which must be conformed to by prudence and utilized by labour to yield shelter and food, have led to the growth of peoples differing in their ways of life, thought and speech. The initial differences so produced are confirmed and perpetuated by the same barriers which divide the faunal or floral regions, the sea, mountains, deserts and the 4e, and much of the course of past history and present politics becomes clear when the combined results of differing race and differing environment are taken into account.' The specialization which accompanies the division of labour has important geographical consequences, for it necessitates communi- i On the influence of land on people see Shaler, Nature and Man in America (New York and London, 1892) ; and Ellen C. Semple's American History and its Geographic Conditions (Boston, 1903cation between communities and the interchange of their pro-ducts. Trade makes it possible to work mineral resources in localities where food can only be grown with great pu a ion. difficulty and expense, or which are even totally barren' and waterless, entirely dependent on supplies from distant sources. The population which can be permanently supported by a given area of land differs greatly according to the nature of the resources and the requirements ofthe people. Pastoral communities are always scattered very thinly over large areas; agricultural populations may be almost equally sparse where advanced methods of agriculture and labour-saving machinery are employed; but where a frugal people are situated on a fertile and inexhaustible soil, such as the deltas and river plains of Egypt, India and China, an enormous population may be supported on a small area. In most cases, however, a very dense population can only be maintained in regions where mineral resources have fixed the site of great manufacturing industries. The maximum density of population which a given region can support is very difficult to determine; it depends partly on the race and standard of culture of the people, partly on the nature and origin of the resources on which they depend, partly on the artificial burdens imposed and very largely on the climate. Density of population is measured by the average number of people residing on a unit of area; but in order to compare one part of the world with another the average should, strictly speaking, be taken for regions of equal size or of equal population; and the portions of the country which are permanently uninhabitable ought to be excluded from the calculation? Considering the average density of population within the political limits of countries, the following list is of some value; the figures for a few smaller divisions of large countries are added (in brackets) for comparison: Average Population on I sq. m. (For 1900 or Igor.) Count n' Density Country. Density of pop. of pop. (Saxony) . . 743 Ceylon . . . 141 4 Belgium . . 589 a Greece . . . 97 Java . . 568 4 European Turkey 90 (England and Wales) 558 Spain . . . 97 (Bengal) . . 495 4 European Russia . 55 4 Holland . 436 Sweden . . . 3o United Kingdom 344 United States 25 Japan . . 317 Mexico . . 18 [PRINCIPLES Italy 293 Norway . . . . i8 China proper 270 4 Persia . . . 15 German Empire 270 New Zealand . . 7 Austria 226 Argentina . . 5 Switzerland . 207 Brazil . . 4'5 France 188 Eastern States of Indian Empire 167 4 Australia . 3 Denmark 16o 4 Dominion of Canada 1.5 Hungary . . 154 4 Siberia I Portugal . . 146 West Australia 0.2 The movement of people from one place to another without the immediate intention of returning is known as migration, and according to its origin it may be classed as centrifugal (directed MlgreUon. from a particular area) and centripetal' (directed towards a particular area). Centrifugal migration is usually a matter of compulsion; it may be necessitated by natural causes, such as a change of climate leading to the withering of pastures or destruction of agricultural land, to inundation, earthquake, pestilence or to an excess of population over means of support; or to artificial causes, such as the wholesale deportation of a conquered people; or to political or religious persecution. In any case the people are driven out by some adverse change; and when the urgency is great they may require to drive out in turn weaker people who occupy a desirable territory, thus propagating the wave of migration, the direction of which is guided by the forms of the land into inevitable channels. Many of the great historic movements of peoples were doubtless due to the gradual change of geographical or climatic conditions; and the slow desiccation of Central Asia has been plausibly suggested as the real cause of the peopling of modern Europe and of the medieval wars of the Old World, the theatres of which were critical points on the great natural lines of communication between east and west. In the case of centripetal migrations people flock to some particular place where exceptionally favourable conditions have been found to exist. The rushes to gold-fields and diamond-fields are typical in-stances; the growth of towns on coal-fields and near other sources of power, and the rapid settlement of such rich agricultural districts as the wheat-lands of the American prairies and great plains are other examples. There is, however, a tendency for people to remain rooted to the 2 See maps of density of population in Bartholomew's great large-scale atlases, Atlas of Scotland and Atlas of England. 8 Almost exclusively industrial. 4 Almost exclusively agricultural. land of their birth, when not compelled or induced by powerful external causes to seek a new home. Thus arises the spirit of patriotism, a product of purely geographical conditions, thereby differing from the sentiment of loyalty, Political which is of racial origin. Where race and soil conspire to aaosn+vtrn evoke both loyalty and patriotism in a people, the moral qualities of a great and permanent nation are secured. It is noticeable that the patriotic spirit is strongest in those places where people are brought most intimately into relation with the land ; dwellers in the mountain or by the sea, and, above all, the people of rugged coasts and mountainous archipelagoes, have always been renowned for love of country, while the inhabitants of fertile plains and trading communities are frequently less strongly attached to their own land. Amongst nomads the tribe is the unit of government, the political bond is personal, and there is no definite territorial association of the people, who may be loyal but cannot be patriotic. The idea of a country arises only when a nation, either homogeneous or composed of several races, establishes itself in a region the boundaries of which may be defined and defended against aggression from without. Political geography takes account of the partition of the earth amongst organized communities, dealing with the relation of races to regions, and of nations to countries, and considering the conditions of territorial equilibrium and instability. The definition of boundaries and their delimitation is one of the most important parts of political geography. Natural boundaries Bound- are always the most definite and the strongest, lending arias themselves most readily to defence against aggression. The sea is the most effective of all, and an island state is recognized as the most stable. Next in importance comes a mountain range, but here there is often difficulty as to the definition of the actual crest-line, and mountain ranges being broad regions, it may happen that a small independent state, like Switzerland or Andorra, occupies the mountain valleys between two or more great countries. Rivers do not form effective international boundaries, although between dependent self-governing communities they are convenient lines of demarcation. A desert, or a belt of country left purposely without inhabitants, like the mark, marches or debatable lands of the middle ages, was once a common means of separating nations which nourished hereditary grievances. The " buffer-state " of modern diplomacy is of the same ineffectual type. A less definite though very practical boundary is that formed by the meeting-line of two languages, or the districts inhabited by two races. The line of fortresses protecting Austria from Italy lies in some places well back from the political boundary, but just inside the linguistic frontier, so as to separate the German and Italian races occupying Austrian territory. Arbitrary lines, either traced from point to point and marked by posts on the ground, or defined as portions of meridians and parallels, are now the most common type of boundaries fixed by treaty. In Europe and Asia frontiers are usually strongly fortified and strictly watched in times of peace as well as during war. In South America strictly defined boundaries are still the exception, and the claims of neighbouring nations have very frequently given rise to war, though now more commonly to arbitration.' The modes of government amongst civilized peoples have little influence on political geography; some republics are as arbitrary and of and exacting in their frontier regulations as some absolute arms monarchies. It is, however, to be noticed that absolute governs went monarchies are confined to the east of Europe and to Asia, Japan being the only established constitutional monarchy east of the Carpathians. Limited monarchies are (with the exception of Japan) peculiar to Europe, and in these the degree of democratic control may be said to diminish as one passes east-wards from the United Kingdom. Republics, although represented in Europe, are the peculiar form of government of America and are unknown in Asia. The forms of government of colonies present a series of transitional types from the autocratic administration of a governor appointed by the home government to complete democratic self-government. The latter occurs only in the temperate possessions of the British empire, in which there is no great preponderance of a coloured native population. New colonial forms have been developed during the partition of Africa amongst European powers, the sphere of influence being especially worthy of notice. This is a vaguer form of control than a protectorate, and frequently amounts merely to an agreement amongst civilized powers to respect the right of one of their number to exercise government within a certain area, if it should decide to do so at any future time. The central governments of all civilized countries concerned with external relations are closely similar in their modes of action, but the internal administration may be very varied. In this respect a .country is either centralized, like the United Kingdom or France, ' For the history of territorial changes in Europe, see Freeman, Historical Geography of Europe, edited by Bury (Oxford), 1903; and for the official definition of existing boundaries, see Hertslet, The Map of Europe by Treaty (4 vols., London, 1875, 1891) ; The Map of Africa by Treaty (3 vols., London, 1896). Also Lord Curzon's Oxford address 99 Froattiet,c (1907). 'For numerous special instances of the determining causes of town sites, see G. G. Chisholm, " On the Distribution of Towns and Villages in England," Geographical Journal (1897), ix. 76, x. 511. The whole subject of anthropogeography is treated in a masterly way by F. Ratzel in his Anthropogeographie (Stuttgart, vol. i. and ed., 1899, vol. ii. 1891), and in his Polstisohe Geographie (Leipzig, 1897). The special question of the reaction of man on his environment is handled by G. P. Marsh in Man and Nature, or Physical Geography as modified by Human Action (London, 1864). For commercial geography see G. G. Chisholm, Manual of Commercial Geography (189o). or federated of distinct self-governing units like Germany (where the units include kingdoms, at least three minor types of monarchies, municipalities and a crown land under a nominated governor), or the United States, where the units are democratic republics. The ultimate cause of the predominant form of federal government may be the geographical diversity of the country, as in the cantons occupying the once isolated mountain valleys of Switzerland, the racial diversity of the people, as in Austria-Hungary, or merely political expediency, as in republics of the American type. The minor subdivisions into provinces, counties and parishes, or analogous areas, may also be related in many cases to natural features or racial differences perpetuate,d by historical causes. The territorial divisions and subdivisions often survive the conditions which led to their origin; hence the study of political geography is allied to history as closely as the study of physical geography is allied to geology, and for the same reason. The aggregation of population in towns was at one time mainly brought about by the necessity for defence, a fact indicated by the defensive sites of many old towns. In later times, Towns. towns have been more often founded in proximity to valuable mineral resources, and at critical points or nodes on lines of communication. These are places where the mode of travelling or of transport is changed, such as seaports, river ports and railway termini, or natural resting-places, such as a ford, the foot of a steep ascent on a road, the entrance of a valley leading up from a plain into the mountains, or a crossing-place of roads or railways.' The existence of a good natural harbour is often sufficient to give origin to a town and to fix one end of a line of land communication. In countries of uniform surface or faint relief, roads and railways may be constructed in any direction without regard to the con-figuration. In places where the low ground is marshy, Lines of roads and railways often follow the ridge-lines of hills, eommunior, as in Finland, the old glacial eskers, which run parallel aatios. to the shore. Wherever the relief of the land is pro- nounced, roads and railways are obliged to occupy the lowest ground winding along the valleys of rivers and through passes in the mountains. In exceptional cases obstructions which it would be impossible or too costly to turn are overcome by a bridge or tunnel, the magnitude of such works increasing with the growth of engineering skill and financial enterprise. Similarly the obstructions offered to water communication by interruption through land or shallows are overcome by cutting canals or dredging out channels. The economy and success of most lines of communication depend on following as far as possible existing natural lines and utilizing existing natural sources of power.' Commercial geography may be defined as the description of the earth's surface with special reference to the discovery, production, transport and exchange of commodities. The transport ommerconcerns land routes and sea routes, the latter being C cia, goo-the more important. While steam has been said to SraP6y. make a ship independent of wind and tide, it is still true that a long voyage even by steam must be planned so as to encounter the least resistance possible from prevailing winds and permanent currents, and this involves the application of oceanographical and meteorological knowledge. The older navigation by utilizing the power of the wind demands a very intimate knowledge of these conditions, and it is probable that a revival of sailing ships may in the present century vastly increase the importance of the study of maritime meteorology. The discovery and production of commodities require a know-ledge of the distribution of geological formations for mineral pro-ducts, of the natural distribution, life-conditions and cultivation or breeding of plants and animals and of the labour market. Attention must also be paid to the artificial restrictions of political geography, to the legislative restrictions bearing on labour and trade as imposed in different countries, and, above all, to the incessant fluctuations of the economic conditions of supply and demandrand the combinations of capitalists or workers which affect the market.' The term " applied geography " has been employed to designate commercial geography, the fact being that every aspect of scientific geography may be applied to practical purposes, including the purposes of trade. But apart from the applied science, there is an aspect of pure geography which concerns the theory of the relation of economics to the surface of the earth. It will be seen that as each successive aspect of geographical science is considered in its natural sequence the conditions become 638 more numerous, complex, variable and practically important. From the underlying abstract mathematical considerations all Con- through the superimposed physical, biological, anthropo- ciusion. logical, political and commercial development of the subject runs the determining control exercised by crust-forms acting directly or indirectly on mobile distributions; and this is the essential principle of geography. (H. R. M.)

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