Comparative geography

by Carl Ritter

Terrace Lands and Rivers in their General Character.

Districts sloping to the sea, or lands of gradation, as we have called them, varying as they do in elevation and in relative situation to each other, are the true mediators between the districts but little above the level of the sea and others much more lofty. At the sources and the mouths of rivers they partake, more or less fully, in the characteristics of both highland and lowland. The manner of their mediation, as determined by the rate of the fall of water and by their direction, gives to every one of these regions of transition its peculiar character, determines its conformation and its relation to the globe. And yet, no more than in lowlands and highlands, can we rid ourselves of some arbitrary data relating to the size of rivers, when we discriminate between those which we call large and those which we call small. As in all other geographical distinctions, we must here be content with arbitrary approximation, and with the ordinary usages of speech. The comparison of streams, in regard to their breadth and fullness, determines their volume; the comparison, in respect of length and tributary waters, determines the compass of the river system. The entire characteristics, breadth, depth of channel, length and extent of drainage, determine the status of the river, whether first, second, or third class, in relation first to those of the same continent, and then to those of the world. The Volga, for instance, is, in relation to Europe, a first-class river, but, like the Danube, in relation to the entire globe, is merely in the second or third rank. Not the length alone determines the importance of rivers. The Thames, one of the smallest streams in Europe, is one of the most important. And aside from commercial considerations, a river of insignificant size can have great influence in consequence of its relation to the entire adjacent region. The little Bavarian Isar, a river which, so far as the great world is concerned, seems to have no importance, receives on the left side the water of 860 tributary brooks, among which are 44 rivulets; on the right bank the water of 433: these 1293 brooks and rivulets pour themselves into the Isar through 103 direct tributaries, and not these alone, but the waters of 136 lakes are embraced within the Isar system! Yet the Isar is only one of 34 branches of the Danube, and of the fourth rank even among them, and the Danube is by no means one of the great rivers of the globe. A short but navigable stream can have great influence over a territory limited in extent, and may make a long but shallow stream sink into insignificance in respect of comparative importance to the world. There are some great streams which are of first magnitude in all their characteristics—rivers which drain millions of square miles in their course to the sea. The number of such is small, however; there are scarcely fifty on the whole globe. Besides these, there is a large number of rivers much shorter, and of much less volume, but not deficient in the attributes which give a stream value to man, and which serve to mediate between highlands and lowlands, to fulfill the needs of navigation and to drain regions of more or less magnitude. These can be classed in four ranks: in the first place absolutely, and in the second place in relation to each continent. Yet, in classing them, it is necessary always to keep in mind that it is not size alone which gives a river its value, but a combination of all its characteristics, and its relative influence on the country through which it runs.

Looking at the direction of streams, we observe that there are some which flow northerly, as for instance those of Siberia, the Nile, the Rhine, the Elbe, and the Weser; there are those which flow southward—the Indus, Ganges, Euphrates, La Plata, Mississippi, and Volga, for example; there are those flowing eastward—Hoang-ho and Yang-tse-Kiang, the Amazon, the Orinoco, and the Danube, for instance; and some westward, instances of which may be found in the Gihon and Sihon, the Senegal, Gambia, Niger, the Colorado, the Seine, Loire, Garonne, and the Spanish rivers which enter the sea in Portugal.

And this characteristic, trite and unmeaning as it may at first seem, establishes, for the area which these rivers water, very diverse conditions. In like manner, too, their position, in relation to the oceans into which they flow, is very influential, in consequence of the action of the tide upon the lower course. The emergence of their head-waters at various altitudes, whether on plateaus of the first or second class, or on mountain tops covered with perpetual snow, gives rise to a great diversity of relations, that makes no one stream on the earth twin brother to any other. Rivers have an individuality which claims recognition, although they are usually summed up in one category.

This diversity in rivers becomes more apparent from a study of the diversified form of the terraces, or grades of transition, through which they pass on their way to the sea.

The great basin of the Nile is divided into three distinct parts or grades—Abyssinia, Nubia, and Egypt; and each of them has long been studied historically and physically. The great basin of the Rhine is also naturally divided into three grades—the Swiss highlands, the German moderate plateau, and the lowlands of Holland. In a similar manner there may almost always be traced in rivers three natural grades, and where they do not have, as in the cases just cited they do have, a historical significance, their physical influence is not hard to trace and to follow into all its analogies.

The word water-shed, now a familiar one, is applied to that point of division where contiguous springs pour their water in different directions. It is not even in a mountainous country necessarily coincident with the highest points of the chain, though it may be; the valleys may slope in such a way as to have more influence in determining the direction of running water than the mountains hard by. Every stream has its own water-shed system, and this system is the real boundary of its basin. If we trace this basin to its very limits on the highlands, we may find, not a mile away, the beginnings of another river, which shall flow in just the contrary direction, as for example in the case of the Rhine and Rhone, the Volga and the Dwina. The sources of the Missouri and of the Columbia lie close together, not a quarter of an hour’s walk apart; yet the waters of one flow into the Atlantic, of the other into the Pacific, and their mouths are almost 2500 miles apart. The Mongolians hold the water-shed in such estimation that they throw up a heap of stones wherever one occurs, establish it a shrine for prayer; and the Toongooses of Siberia never pass by one without casting a cedar branch upon the stone heap, that, to use their expression, “the holy mountain that parts the waters may not lessen, but increase.”

The main channel is the stream proper; the others are tributaries. The longest tributaries coming in from the region where the river proper rises, can be grouped intimately with the source of the main current, hardly distinguished from it in relative importance—the two, for instance, in the Nile, the five in the Indus, two in the Ganges, three in the Amazon, etc. All form in their confluence the real channel of the river. And the entire body of tributaries, taken in conjunction with the river proper, forms the river system, and the district which they all drain is their true reciprocal. The two, in their mutual action and reaction, form a whole, and are always thought of together. The source and the mouth are the beginning and the end of the whole system; the main channel and the circuit of water-shed, the center and the circumference of it. All the tributaries in their union constitute what may be called the arterial system of the river basin; the form of each and the characteristics of each are analogous to those of the whole, only in reduced pattern. The network which all the tributaries make is often surprisingly intricate. The symmetry with which the main characteristics of a river system are carried into the details, even of its smallest accessories, can only be compared to that observable in the architectural regularity of a tree, as it expands from the main trunk into the countless symmetrical branches.

There are some rivers which are entirely independent of tributaries—which pursue their way to the sea entirely alone. Such rivers, however, never belong to the first class; they are always of subordinate magnitude, and the humblest of them are mere coast torrents, like those west of the Andes. Others find their way to no ocean, but lose themselves in an inland sea or lake, as the Volga does in the Caspian; as the Gihon and the Sihon do in the Aral; as the Jordan does in the Dead Sea. Others disappear in sand wastes or in morasses; such are the rivers of the African steppes. Others are blocked up, as it were, by the tidal wave of the ocean, and are thus converted into estuary lakes.

There are some rivers, also, which remain equally or nearly equally full the whole year through; there are others which have their seasons of overflow: the Nile, for instance, and many rivers whose basin lies within the region of tropical rains; there are temporary rivers, now full, now empty, which, if they do not leave, like the torrents of Arabia, a perfectly dry bed, are traced in the dry season by a row of stagnant lakes, such, for example, as are found in the swampy lands of Australia.