Modern Geography

n place as to the exact limits of its field of action, and many definitions have been proposed with the object of setting forth these limits as clearly as possible. But it is sufficient for our purpo

obviously necessary to look at some general points conne

the concern of special sciences, and not of the geographer proper. His business it is to take the facts furnished by the meteorologists, the physicists, the geologists, and so forth, and with these facts in hand to proceed to consider the effect of the interaction of earth and water a

ws that the water accumulates, so that we can distinguish between the dry land and the ocean beds. Both chemically and physically the fluid hydrosphere differs markedly from the solid lithosphere, and it is, above all, the physical differences which are of supreme importance to the geographer. Beca

any globe will show that land and ocean are very unequally distributed. The great land masses cluster round the North Pole, while the southern hemisphere consists largely of water. We thus have a land hemisphere and a water one. According to recent calculations the oceans occupy some 72 per cent. of the entire surface

which the arrangement of land and water has had upon that part of the life of the earth which was evolved in late geological time. Though the geographer for convenience' sake recognizes three separate continents in the Old World-Europe, Asia and Africa-yet these form practically one

ny remarkable resemblances between the faunas of Europe, of Asia and of Africa, and a similar, if less marked, resemblance between those of North America on the one hand and of Europe and temperate Asia on the other. On the other hand, the two great land mas

of Africa from participation in them. America developed a relatively high civilisation of its own, but as the icefields and ice-pack of the north formed a greater barrier to the migrations of man than

group tend to acquire characters fitting them for this restricted area. But if the area is open, constantly or periodically, to incursions of organisms from adjacent areas, then, with the widening of the environment, and the greater intensity of the struggle for existence, evolution is quickened and new characters appear. The men of the Eurasian continent learnt, on the fierce b

terfere with the circulation of the atmosphere, many physical phenomena occur in a more marked and orderly fashion than to the north. The westerly winds of the south blow with a force and a constancy which makes it impossible to compare them with the more variable westerlies of the north. Even the ocean currents of the south seem to show more cons

e earth, by the existence of vast depressions in which the water accumulates, and of relative elevations from which it flows. But the minor details of relief, hill and v

and to the changes of the seasons, with corresponding variations in temperature; to the fluctuations of the weather; to running water, and so forth. In the great ocean depths at least, on the other hand, the conditions are remarkably uniform. Neither diurnal nor seasonal changes have here any effec

Shelf, and its seaward boundary for convenience' sake is taken at a depth of 100 fathoms, or 600 feet. Within this zone the influence of the land is still felt, and some of the characters of land surfaces appear. Thus we sometimes find that river valleys are prolonged outwards over th

coarser lying near the shore-line, the finer extending outwards to the steep seaward slope. This rapid slope leads down to the more or less uniform ocean plateau, whose surface is broken by the gr

s compared with the land surface it displays great constancy. While the land surface is constantly changing owing to the varying forces w

nd of these forces the most important to the geographer is running water. It is running water, aided by other agents, which carves the land into hill and valley, which produces gorge and lake, on

rst produce irregularities and then finally remove these, until the whole surface is once again almost level. The whole globe would thus be reduced to the condition o

rface of the globe at the present time every stage in the process occurs, and everywhere the question whether a particular land area has been exposed for a relatively long or for a relatively short period to the forces o

lakes and waterfalls have largely disappeared. To this condition the term mature has been applied. At a still later stage the land surface has been so worn by the eroding forces that the whole process of erosion is slackened, and an uplift must occur before the erosive forces regain their lost strength. This is the so-called "cycle of normal erosion," but it is const

ses of rock rubbish which are accumulating round them, have obviously only been exposed for a geologically short period to the action of the atmosphere and of running water. When examined such mountain chains are all found to have the same peculiarities of internal form, the rocks composing them being elabor

ce to form the Pyrenees, the Alps, the Caucasus and the Himalayas, but the Atlas Mountains belong to the same series, a

formed mountain regions but are now mostly worn down to uplands. The lines (2) show the regions affected by Tertiary folding, largely occupied by moun

pland type but with rounded and smoothed forms, which are sometimes almost reduced to the condition of a plain. Such regions occur in Ireland, in the west of Great Britain generally, in Brittany, in the central plateau of France, in the Ardennes, in Bohemia, in the central plateau of Spain, in Scandinavia, and so forth. Between these relatively elevated areas we have plains and low-lying r

ing agents, must we not suppose that the folded and contorted uplands of Europe and elsewhere are the last remnants of very ancient mountain chains? It is they which form the

he oldest, and include as their most generally interesting member the Carboniferous rocks, with their coal-bearing beds, so important in the modern industrial world. Second, we have the Secondary beds, the most interestin

e folding and mountain formation, took place. The geologists distinguish no less than three separate periods of folding in Primary times. It is not necessary for us to consider these in detail; their total result was to produce the mountain regions whose worn-down stumps now form those uplands which we have described in Europe. But they do not occur in Europe alone. That vast and relatively infertile area in Eastern Canada which geologists cal

ts of the globe, the result being the appearance at the surface of the great mountain chains of the present day. The structure of these chains makes them relatively unstable, and the forces of eros

areas form plains or basins, where the rocks are but slightly tilted, or show a very simple form of folding. In Eur

t plains, filling what seems once to have been a great gulf between the ol

re geography it seems desirable to distinguish between those remnants of ancient mountains which form the backbone of the continents, the rece

d slowly emerging above sea-level, or even with the effect of heavy rain upon sloping ground unprotected by a covering of vegetation. Alike in the one case and in the other the first effect is the formation

rce. The dotted line BC shows an earlier stage, when there are smooth reaches and rapid reaches wi

that the Loire is a mature river, its profile nearly co

stream proper forming a canal which drains the basin, while below, where the torrent debouches on the low ground, we find that it spreads out fanwise and throws down its load of débris to form a cone (c?ne de déjection).

r is at its maximum, and where it has acquired a load of débris by means of which it carves out its bed. The excavation of the bed therefore proceeds from below upwards towards the collecting basin. The result is that the slope of the valley floor diminishes as we pass from the upper region to the lower, owing to the levelling effect of erosi

rious drawing of a profile in order to determine the extent to which the process of excavation has been carried. The existence of rapids, of waterfalls, the alternation of swift and slow-flowing reaches are all proofs that it has not been carried far. In short, if a river is navigable, the navigable reach at least is mature; if it is capable of furnis

The youthful river, with its interrupted slope, its lakes and falls, does not permit the water to flow off with the same

he bed of the river, and that the normal course of events is the transition from waterfall to rapid, and from rapid to stream flowing quietly at the bottom of a rocky gorge. Long gorges or canyons tend to occur in

ource retreats further and further into the mountain. In regions of abundant rainfall every slope is abundantly supplied with streams, and therefore those streams which cut back their region of origin most rapidly will necessarily encroach upon

hat is, for the most part they are very youthful streams. In some cases, however, e. g. in the case of the Dranse and the Visp, the drainage is of a more advanced character, and we find a large stream with tributaries of considerable size as distinct from mere torrents. A glance at any great river system on the map, e. g. the Mississippi, the Amazon, etc., will show that the cond

map to illustra

ous bend, or elbow. Mr. Hinxman points out that this curious condition can be explained on the supposition that the River Eidart, shown on the map to the north of the bend, once formed the headwaters of the Feshie, which cut its valley back until it captured the headwaters of the Geldie, and thus brought water which formerly flowed into the Dee int

sharp bend, the so-called elbow of capture, on a river in close proximity to another stream affords in itself a ce

s case is that of the Casiquiare, a river in South America which connects together the two systems of the Amazon and the Orinoco, while another is the connection recently discovered by Captain Lenfant, a Frenc

rmed by the Wolds of Yorkshire and Lincolnshire, which consists of hard rock. At one time it is probable that the rivers of Yorkshire entered the sea separately, while the other great factor of the Humber, the Trent, mingled its waters with the present Witham. At this time the weathering of the land surface had not reached its present stage so the land would lie higher. In what is now

f the Tyne and Aire Gaps, and the peculiar character of the ri

streams have more erosive power than the easterly. But the special interest of the case is simply that it may serve to suggest a fact not at first sight obvious, which is that water-partings are excessively unstable features. One set of streams is continually striving to encroach upon the others, and by capturing their headwaters to reduce their erosive po

ssistance of the other agents of denudation tends to reduce the mountains to plains-or at least "peneplains." The deduction is, of course, old enough, but the recen

ldie, but is now a dry valley. Such "gaps," as they are called, are present where recent capture has occurred, and where they occur in hilly country they sometimes form useful passes, permitting the construction of an easy road across the hills. A good example is the Aire Gap (see fig. 5) in the Pennine range of Great Britain, appa

n chains to a much greater extent than running water; but here, as in many other