FOOTNOTES:

FOOTNOTES:[38]Ruskin.[39]The Glaciers of the Alps.[40]Ossian.[41]Bullar,Azores.[42]Tennyson.[43]See especially Heim's great work,Unt. ü. d. Mechanismus der Gebirgsbildung.[44]In the last 150 years more than 1000 are recorded.[45]Letters from High Latitudes.[46]Glaciers of the Alps.[47]Mountaineering in 1861.

[38]Ruskin.

[39]The Glaciers of the Alps.

[40]Ossian.

[41]Bullar,Azores.

[42]Tennyson.

[43]See especially Heim's great work,Unt. ü. d. Mechanismus der Gebirgsbildung.

[44]In the last 150 years more than 1000 are recorded.

[45]Letters from High Latitudes.

[46]Glaciers of the Alps.

[47]Mountaineering in 1861.

Of all inorganic substances, acting in their own proper nature, and without assistance or combination, water is the most wonderful. If we think of it as the source of all the changefulness and beauty which we have seen in the clouds; then as the instrument by which the earth we have contemplated was modelled into symmetry, and its crags chiselled into grace; then as, in the form of snow, it robes the mountains it has made, with that transcendent light which we could not have conceived if we had not seen; then as it exists in the foam of the torrent, in the iris which spans it, in the morning mist which rises from it, in the deep crystalline pools which mirror its hanging shore, in the broad lake and glancing river, finally, in that which is to all human minds the best emblem of unwearied, unconquerable power, the wild, various, fantastic, tameless unity of the sea; what shall we compare to this mighty, this universal element, for glory and for beauty? or how shall we follow its eternal cheerfulness of feeling? It is like trying to paint a soul.—Ruskin.

RYDAL WATER. To face page 251.RYDAL WATER.To face page 251.

In the legends of ancient times running water was proof against all sorcery and witchcraft:

No spell could stay the living tideOr charm the rushing stream.[48]

There was much truth as well as beauty in this idea.

Flowing waters, moreover, have not only power to wash out material stains, but they also clear away the cobwebs of the brain—the results of over incessant work—and restore us to health and strength.

Snowfields and glaciers, mountain torrents, sparkling brooks, and stately rivers, meres and lakes, and last, not least, the great ocean itself, all alike possess this magic power.

"When I would beget content," says Izaak Walton, "and increase confidence in the power and wisdom and providence of Almighty God, I will walk the meadows by some gliding stream, and there contemplate the lilies that take no care, and those very many other little living creatures that are not only created, but fed (man knows not how) by the goodness of the God of Nature, and therefore trust in Him;" and in his quaint old language he craves a special blessing on all those "that are true lovers of virtue, and dare trust in His Providence, and be quiet, and go a angling."

At the water's edge flowers are especially varied and luxuriant, so that the banks of a river are a long natural garden of tall and graceful grasses and sedges, the Meadow Sweet, the Flowering Rush, the sweet Flag, the Bull Rush, Purple Loosestrife, Hemp Agrimony, Dewberry, Forget-me-not, and a hundred more, backed by Willows, Alders, Poplars, and other trees.

The Animal world, if less conspicuous to the eye, is quite as fascinating to the imagination.Here and there a speckled Trout may be detected (rather by the shadow than the substance) suspended in the clear water, or darting across a shallow; if we are quiet we may see Water Hens or Wild Ducks swimming among the lilies, a Kingfisher sitting on a branch or flashing away like a gleam of light; a solemn Heron stands maybe at the water's edge, or slowly rises flapping his great wings; Water Rats, neat and clean little creatures, very different from their coarse brown namesakes of the land, are abundant everywhere; nor need we even yet quite despair of seeing the Otter himself.

Insects of course are gay, lively, and innumerable; but after all the richest fauna is that visible only with a microscope.

"To gaze," says Dr. Hudson, "into that wonderful world which lies in a drop of water, crossed by some stems of green weed, to see transparent living mechanism at work, and to gain some idea of its modes of action, to watch a tiny speck that can sail through the prick of a needle's point; to see its crystal armour flashing with ever varyingtint, its head glorious with the halo of its quivering cilia; to see it gliding through the emerald stems, hunting for its food, snatching at its prey, fleeing from its enemy, chasing its mate (the fiercest of our passions blazing in an invisible speck); to see it whirling in a mad dance, to the sound of its own music, the music of its happiness, the exquisite happiness of living—can any one, who has once enjoyed this sight, ever turn from it to mere books and drawings, without the sense that he has left all Fairyland behind him?"[49]

The study of Natural History has indeed the special advantage of carrying us into the country and the open air.

Lakes are even more restful than rivers or the sea. Rivers are always flowing, though it may be but slowly; the sea may rest awhile, now and then, but is generally full of action and energy; while lakes seem to sleep and dream. Lakes in a beautiful country are like silver ornaments on a lovely dress, like liquid gems in a beautiful setting, or bright eyes in a lovely face. Indeed as we gaze down on a lake from some hill or cliff it almost looks solid, like some great blue crystal.

WINDERMERE. To face page 254.WINDERMERE.To face page 254.

It is not merely for purposes of commerce or convenience that men love to live near rivers.

Let me live harmlessly, and near the brinkOf Trent or Avon have my dwelling-place;Where I may see my quill, or cork, down sink,With eager bite of pike, or bleak, or dace;And on the world and my Creator think:While some men strive ill-gotten goods t' embrace:And others spend their time in base excessOf wine; or worse, in war, or wantonness.Let them that will, these pastimes still pursue,And on such pleasing fancies feed their fill:So I the fields and meadows green may viewAnd daily by fresh rivers walk at will,Among the daisies and the violets blue,Red hyacinth and yellow daffodil.[50]

Let them that will, these pastimes still pursue,And on such pleasing fancies feed their fill:So I the fields and meadows green may viewAnd daily by fresh rivers walk at will,Among the daisies and the violets blue,Red hyacinth and yellow daffodil.[50]

It is interesting and delightful to trace a river from its source to the sea.

"Beginning at the hill-tops," says Geikie, "we first meet with the spring or 'well-eye,' from which the river takes its rise. A patch of bright green, mottling the brown heathyslope, shows where the water comes to the surface, a treacherous covering of verdure often concealing a deep pool beneath. From this source the rivulet trickles along the grass and heath, which it soon cuts through, reaching the black, peaty layer below, and running in it for a short way as in a gutter. Excavating its channel in the peat, it comes down to the soil, often a stony earth bleached white by the peat. Deepening and widening the channel as it gathers force with the increasing slope, the water digs into the coating of drift or loose decomposed rock that covers the hillside. In favourable localities a narrow precipitous gully, twenty or thirty feet deep, may thus be scooped out in the course of a few years."

If, however, we trace one of the Swiss rivers to its source we shall generally find that it begins in a snow field ornévénestled in a shoulder of some great mountain.

Below thenévélies a glacier, on, in, and under which the water runs in a thousand little streams, eventually emerging at the end, in some cases forming a beautiful bluecavern, though in others the end of the glacier is encumbered and concealed by earth and stones.

Fig. 24.—Upper Valley of St. Gotthard.Fig. 24.—Upper Valley of St. Gotthard.

The uppermost Alpine valleys are perhaps generally, though by no means always, alittle desolate and severe, as, for instance, that of St. Gotthard (Fig. 24). The sides are clothed with rough pasture, which is flowery indeed, though of course the flowers are not visible at a distance, interspersed with live rock and fallen masses, while along the bottom rushes a white torrent. The snowy peaks are generally more or less hidden by the shoulders of the hills.

The valleys further down widen and become more varied and picturesque. The snowy peaks and slopes are more often visible, the "alps" or pastures to which the cows are taken in summer, are greener and dotted with the huts or châlets of the cow-herds, while the tinkling of the cowbells comes to one from time to time, softened by distance, and suggestive of mountain rambles. Below the alps there is generally a steeper part clothed with Firs or with Larches and Pines, some of which seem as if they were scaling the mountains in regiments, preceded by a certain number of skirmishers. Below the fir woods again are Beeches, Chestnuts, and other deciduous trees, while the centralcultivated portion of the valley is partly arable, partly pasture, the latter differing from our meadows in containing a greater variety of flowers—Campanulas, Wild Geraniums, Chervil, Ragged Robin, Narcissus, etc. Here and there is a brown village, while more or less in the centre hurries along, with a delightful rushing sound, the mountain torrent, to which the depth, if not the very existence of the valley, is mainly due. The meadows are often carefully irrigated, and the water power is also used for mills, the streams seeming to rush on, as Ruskin says, "eager for their work at the mill, or their ministry to the meadows."

Apart from the action of running water, snow and frost are continually disintegrating the rocks, and at the base of almost any steep cliff may be seen a slope of debris (as in Figs. 25, 26). This stands at a regular angle—the angle of repose—and unless it is continually removed by a stream at the base, gradually creeps up higher and higher, until at last the cliff entirely disappears.

Fig. 25.—Section of a river valley. The dotted line shows a slope or talus of debris.Fig. 25.—Section of a river valley. The dotted line shows a slope or talus of debris.

Sometimes the two sides of the valley approach so near that there is not even room for the river and the road: in that case Nature claims the supremacy, and the road has to be carried in a cutting, or perhaps in a tunnel through the rock. In other cases Nature is not at one with herself. In many places the debris from the rocks above would reach right across the valley and dam up the stream. Then arises a struggle between rock and river, but the river is always victorious in the end; even if dammed back for a while, it concentrates its forces, rises up the rampart of rock, rushes over triumphantly, resumes its original course, and gradually carries the enemy away.

Fig. 26.—Valley of the Rhone, with the waterfall of Sallenches, showing talus of debris.Fig. 26.—Valley of the Rhone, with the waterfall of Sallenches, showing talus of debris.

Another prominent feature in many valleys is afforded by the old river, or lake, terraces, which were formed at a time when the river ran at a level far above its present bed.

Thus many a mountain valley gives some such section as the following.

Fig. 27.—A, present river valley; B, old river terrace.Fig. 27.—A, present river valley; B, old river terrace.

First, a face of rock, very steep, and in some places almost perpendicular; secondly, a regular talus of fallen rocks, stones, etc., as shown in the view of the Rhone Valley (Fig. 26), which takes what is known as the slope of repose, at an angle which depends on the character of the material. As a rule for loose rock fragments it may be taken roughly to be an angle of about 45°. Then an irregular slope followed in many places by one or more terraces, and lastly the present bed of the river.

Fig. 28.—Diagram of an Alpine valley showing a river cone. Front view.Fig. 28.—Diagram of an Alpine valley showing a river cone. Front view.

The width or narrowness of the valley in relation to its depth depends greatly on the condition of the rocks, the harder and tougher they are the narrower as a rule being the valley.

From time to time a side stream enters the main valley. This is itself composed of many smaller rivulets. If the lateral valleys are steep, the streams bring with them, especially after rains, large quantities of earth and stones. When, however, they reach the main valley, the rapidity of the current being less, their power of transport also diminishes, and they spread out the material which they carry down in a depressed cone (Figs. 28, 29, 31, 32).

A side stream with its terminal cone, when seen from the opposite side of the valley, presents the appearance shown in Figs. 28, 31, or, if we are looking down the valley, as in Figs. 29, 32, the river being often driven to one side of the main valley, as, for instance, is the case in the Valais, near Sion, where the Rhone (Fig. 30) is driven out of its course by, and forms a curve round, the cone brought down by the torrent of the Borgne.

Fig. 29.—Diagram of an Alpine valley, showing a river cone. Lateral view.Fig. 29.—Diagram of an Alpine valley, showing a river cone. Lateral view.

Sometimes two lateral valleys (see Plate) come down nearly opposite one another, so that the cones meet, as, for instance, some little way below Vernayaz, and, indeed, in several other places in the Valais (Fig. 31). Or more permanent lakes may be due to a ridge of rock running across the valley, as, for instance, just below St. Maurice in the Valais.

Fig. 30.Fig. 30.

VIEW IN THE VALAIS BELOW ST. MAURICE. To face page 266.VIEW IN THE VALAIS BELOW ST. MAURICE.To face page 266.

Fig. 31.—View in the Rhone Valley, showing a lateral cone.Fig. 31.—View in the Rhone Valley, showing a lateral cone.

Almost all river valleys contain, or have contained, in their course one or more lakes, and where a river falls into a lake a cone like those just described is formed, and projects into the lake. Thus on the Lake of Geneva, between Vevey and Villeneuve (see Fig. 33), there are several such promontories, eachmarking the place where a stream falls into the lake.

Fig. 32.—View in the Rhone Valley, showing the slope of a river cone.Fig. 32.—View in the Rhone Valley, showing the slope of a river cone.

The Rhone itself has not only filled up what was once the upper end of the lake,but has built out a strip of land into the water.

Fig. 33.—Shore of the Lake of Geneva, near Vevey.Fig. 33.—Shore of the Lake of Geneva, near Vevey.

That the lake formerly extended some distance up the Valais no one can doubt who looks at the flat ground about Villeneuve.The Plate opposite, from a photograph taken above Vevey, shows this clearly. It is quite evident that the lake must formerly have extended further up the valley, and that it has been filled up by material brought down by the Rhone, a process which is still continuing.

At the other end of the lake the river rushes out 15 feet deep of "not flowing, but flying water; not water neither—melted glacier matter, one should call it; the force of the ice is in it, and the wreathing of the clouds, the gladness of the sky, and the countenance of time."[51]

VIEW UP THE VALAIS FROM THE LAKE OF GENEVA. To face page 270.VIEW UP THE VALAIS FROM THE LAKE OF GENEVA.To face page 270.

In flat countries the habits of rivers are very different. For instance, in parts of Norfolk there are many small lakes or "broads" in a network of rivers—the Bure, the Yare, the Ant, the Waveney, etc.—which do not rush on with the haste of some rivers, or the stately flow of others which are steadily set to reach the sea, but rather seem like rivers wandering in the meadows on a holiday. They have often no natural banks, but are bounded by dense growths of tall grasses, Bulrushes, Reeds, and Sedges, interspersed with the spires of the purple Loosestrife, Willow Herb, Hemp Agrimony, and other flowers, while the fields are very low and protected by dykes, so that the red cattle appear to be browsing below the level of the water; and as the rivers take most unexpected turns, the sailing boats often seem (Fig. 34) as if they were in the middle of the fields.

Fig. 34.—View in the district of the Broads, Norfolk.Fig. 34.—View in the district of the Broads, Norfolk.

At present these rivers are restrained in their courses by banks; when left free theyare continually changing their beds. Their courses at first sight seem to follow no rule, but, as it is termed, from a celebrated river of Asia Minor, to "meander" along without aim or object, though in fact they follow very definite laws.

Finally, when the river at length reaches the sea, it in many cases spreads out in the form of a fan, forming a very flat cone or "delta," as it is called, from the Greek capital Δ, a name first applied to that of the Nile, and afterwards extended to other rivers. This is due to the same cause, and resembles, except in size, the comparatively minute cones of mountain streams.

Fig. 35.Fig. 35.

Fig. 35 represents the delta of the Po, and it will be observed that Adria, once a great port, and from which the Adriatic was named, is now more than 20 miles from the sea. Perhaps the most remarkable case is that of the Mississippi (Fig. 36), the mouths of which project into the sea like a hand, or like the petals of a flower. For miles the mud is too soft to support trees, but is covered by sedges (Miegea); the banks of mud gradually become too soft and mobile even for them. The pilots who navigate ships up the river live in frail houses resting on planks, and kept in place by anchors. Still further, andthe banks of the Mississippi, if banks they can be called, are mere strips of reddish mud, intersected from time to time by transverse streams of water, which gradually separatethem into patches. These become more and more liquid, until the land, river, and sea merge imperceptibly into one another. The river is so muddy that it might almost be called land, and the mud so saturated by water that it might well be called sea, so that one can hardly say whether a given spot is on the continent, in the river, or on the open ocean.

Fig. 36.Fig. 36.

FOOTNOTES:[48]Leyden.[49]Dr. Hudson, Address to the Microscopical Society, 1889.[50]F. Davors.[51]Ruskin.

[48]Leyden.

[49]Dr. Hudson, Address to the Microscopical Society, 1889.

[50]F. Davors.

[51]Ruskin.

In the last chapter I have alluded to the wanderings of rivers within the limits of their own valleys; we have now to consider the causes which have determined the directions of the valleys themselves.

If a tract of country were raised up in the form of a boss or dome, the rain which fell on it would partly sink in, partly run away to the lower ground. The least inequality in the surface would determine the first directions of the streams, which would carry down any loose material, and thus form little channels, which would be gradually deepened and enlarged. It is as difficult for a river as for a man to get out of a groove.

In such a case the rivers would tend to radiate with more or less regularity from the centre or axis of the dome, as, for instance, in our English lake district (Fig. 37). Derwent Water, Thirlmere, Coniston Water, and Windermere, run approximately N. and S.; Crummock Water, Loweswater, and Buttermere N.W. by S.E.; Waste Water, Ullswater, and Hawes Water N.E. by S.W.; while Ennerdale Water lies nearly E. by W. Can we account in any way, and if so how, for these varied directions?

The mountains of Cumberland and Westmoreland form a more or less oval boss, the axis of which, though not straight, runs practically from E.N.E. to W.S.W., say from Scaw Fell to Shap Fell; and a sketch map shows us almost at a glance that Derwent Water, Thirlmere, Ullswater, Coniston Water, and Windermere run at right angles to this axis; Ennerdale Water is just where the boss ends and the mountains disappear; while Crummock Water and Waste Water lie at the intermediate angles.

Fig. 37.—Map of the Lake District.Fig. 37.—Map of the Lake District.

So much then for the direction. We have still to consider the situation and origin, and it appears that Ullswater, Coniston Water, the River Dudden, Waste Water, and Crummock Water lie along the lines of old faults, which no doubt in the first instance determined the flow of the water.

Take another case. In the Jura the valleys are obviously (see Fig. 18) in many cases due to the folding of the strata. It seldom happens, however, that the case is so simple. If the elevation is considerable the strata are often fractured, and fissures are produced. Again if the part elevated contains layers of more than one character, this at once establishes differences. Take, for instance, the Weald of Kent (Figs. 38, 39). Here we have (omitting minor layers) four principal strata concerned, namely, the Chalk, Greensand, Weald Clay, and Hastings Sands.

Fig. 38.Fig. 38.—a, a, Upper Cretaceous strata, chiefly Chalk, forming the North and South Downs;b, b, Escarpment of Lower Greensand, with a valley between it and the Chalk;c, c, Weald Clay, forming plains;d, Hills formed of Hastings Sand and Clay. The Chalk, etc., once spread across the country, as shown in the dotted lines.

The axis of elevation runs (Fig. 39) from Winchester by Petersfield, Horsham, and Winchelsea to Boulogne, and as shown in the following section, taken from Professor Ramsay, we have on each side of the axis two ridges or "escarpments," one that of the Chalk, the other that of the Greensand, while between the Chalk and the Greensand is a valley, and between the Greensand and the ridge of Hastings Sand an undulating plain, in each case with a gentle slope from about where the London and Brighton railway crosses the Weald towards the east. Under these circumstances we might have expected that the streams draining the Weald would have run in the direction of the axis of elevation, and at the bases of the escarpments, as in fact the Rother does for part of its course, into the sea between the North and South Downs, instead of which as a rule they run north and south, cutting in some cases directly through the escarpments; on the north, for instance, the Wye, the Mole, the Darenth, the Medway, and the Stour; and on the south the Arun, the Addur, the Ouse, and the Cuckmere.

Fig. 39.—Map of the Weald of Kent.Fig. 39.—Map of the Weald of Kent.

They do not run in faults or cracks, and it is clear that they could not have excavated their present valleys under circumstances such as now exist. They carry us back indeed to a time when the Greensand and Chalk were continued across the Weald in a great dome, as shown by the dotted lines in Fig. 38. They then ran down the slope of the dome, and as the Chalk and Greensand gradually weathered back, a process still in operation, the rivers deepened and deepened their valleys, and thus were enabled to keep their original course.

Other evidence in support of this view is afforded by the presence of gravel beds in some places at the very top of the Chalk escarpment—beds which were doubtless deposited when, what is now the summit of a hill, was part of a continuous slope.

The course of the Thames offers us a somewhat similar instance. It rises on the Oolitesnear Cirencester, and cuts through the escarpment of the Chalk between Wallingford and Reading. The cutting through the Chalk has evidently been effected by the river itself. But this could not have happened under existing conditions. We must remember, however, that the Chalk escarpment is gradually moving eastwards. The Chalk escarpments indeed are everywhere, though of course only slowly, crumbling away. Between Farnham and Guildford the Chalk is reduced to a narrow ridge known as the Hog's Back. In the same way no doubt the area of the Chalk formerly extended much further west than it does at present, and, indeed, there can be little doubt, somewhat further west than the source of the Thames, almost to the valley of the Severn. At that time the Thames took its origin in a Chalk spring. Gradually, however, the Chalk was worn away by the action of weather, and especially of rain. The river maintained its course while gradually excavating, and sinking deeper and deeper into, the Chalk. At present the river meets the Chalk escarpmentnear Wallingford, but the escarpment itself is still gradually retreating eastward.

So, again, the Elbe cuts right across the Erz-Gebirge, the Rhine through the mountains between Bingen and Coblenz, the Potomac, the Susquehannah, and the Delaware through the Alleghanies. The case of the Dranse will be alluded to further on (p. 292). In these cases the rivers preceded the mountains. Indeed as soon as the land rose above the waters, rivers would begin their work, and having done so, unless the rate of elevation of the mountain exceeded the power of erosion of the river, the two would proceed simultaneously, so that the river would not alter its course, but would cut deeper and deeper as the mountain range gradually rose.

Rivers then are in many cases older than mountains. Moreover, the mountains are passive, the rivers active. Since it seems to be well established that in Switzerland a mass, more than equal to what remains, has been removed; and that many of the present mountains are not sites which were originallyraised highest, but those which have suffered least, it follows that if in some cases the course of the river is due to the direction of the mountain ridges, on the other hand the direction of some of the present ridges is due to that of the rivers. At any rate it is certain that of the original surface not a trace or a fragment remainsin situ. Many of our own English mountains were once valleys, and many of our present valleys occupy the sites of former mountain ridges.

Heim and Rütimeyer point out that of the two factors which have produced the relief of mountain regions, the one, elevation, is temporary and transitory; the other, denudation, is constant, and gains therefore finally the upper hand.

We must not, however, expect too great regularity. The degree of hardness, the texture, and the composition of the rocks cause great differences.

On the other hand, if the alteration of level was too rapid, the result might be greatly to alter the river courses. Mr. Darwin mentions such a case, which, moreover,is perhaps the more interesting as being evidently very recent.

"Mr. Gill," he says, "mentioned to me a most interesting, and as far as I am aware, quite unparalleled case, of a subterranean disturbance having changed the drainage of a country. Travelling from Casma to Huaraz (not very far distant from Lima) he found a plain covered with ruins and marks of ancient cultivation, but now quite barren. Near it was the dry course of a considerable river, whence the water for irrigation had formerly been conducted. There was nothing in the appearance of the water-course to indicate that the river had not flowed there a few years previously; in some parts beds of sand and gravel were spread out; in others, the solid rock had been worn into a broad channel, which in one spot was about 40 yards in breadth and 8 feet deep. It is self-evident that a person following up the course of a stream will always ascend at a greater or less inclination. Mr. Gill therefore, was much astonished when walking up the bed of this ancient river, to find himself suddenly goingdownhill. He imagined that the downward slope had a fall of about 40 or 50 feet perpendicular. We here have unequivocal evidence that a ridge had been uplifted right across the old bed of a stream. From the moment the river course was thus arched, the water must necessarily have been thrown back, and a new channel formed. From that moment also the neighbouring plain must have lost its fertilising stream, and become a desert."[52]

The strata, moreover, often—indeed generally, as we have seen, for instance, in the case of Switzerland—bear evidence of most violent contortions, and even where the convulsions were less extreme, the valleys thus resulting are sometimes complicated by the existence of older valleys formed under previous conditions.

In the Alps then the present configuration of the surface is mainly the result of denudation. If we look at a map of Switzerland we can trace but little relation between the river courses and the mountain chains.

Fig. 40.—Sketch Map of the Swiss Rivers.Fig. 40.—Sketch Map of the Swiss Rivers.

The rivers, as a rule (Fig. 40), run either S.E. by N.W., or, at right angles to this, N.E. and S.W. The Alps themselves follow asomewhat curved line from the Maritime Alps, commencing with the islands of Hyères, by Briancon, Martigny, the Valais, Urseren Thal, Vorder Rhein, Innsbruck, Radstadt, and Rottenmann to the Danube, a little below Vienna,—at first nearly north and south, but gradually curving round until it becomes S.W. by N.E.

The central mountains are mainly composed of Gneiss, Granite, and crystalline Schists: the line of junction between these rocks and the secondary and tertiary strata on the north, runs, speaking roughly, from Hyères to Grenoble, and then by Albertville, Sion, Chur, Inns, bruck, Radstadt, and Hieflau, towards Vienna. It is followed (in some part of their course) by the Isère, the Rhone, the Rhine, the Inn, and the Enns. One of the great folds shortly described in the preceding chapter runs up the Isère, along the Chamouni Valley, up the Rhone, through the Urseren Thal, down the Rhine Valley to Chur, along the Inn nearly to Kufstein, and for some distance along the Enns. Thus, then, five great rivers have taken advantage of this main fold, each ofthem eventually breaking through into a transverse valley.

The Pusterthal in the Tyrol offers us an interesting case of what is obviously a single valley, which has, however, been slightly raised in the centre, near Toblach, so that from this point the water flows in opposite directions—the Drau eastward, and the Rienz westward. In this case the elevation is single and slight: in the main valley there are several, and they are much loftier, still we may, I think, regard that of the Isère from Chambery to Albertville, of the Rhone from Martigny to its source, of the Urseren Thal, of the Vorder Rhine from its source to Chur, of the Inn from Landeck to below Innsbruck, even perhaps of the Enns from Radstadt to Hieflau as in one sense a single valley, due to one of these longitudinal folds, but interrupted by bosses of gneiss and granite,—one culminating in Mont Blanc, and another in the St. Gotthard,—which have separated the waters of the Isère, the Rhone, the Vorder Rhine, the Inn, and the Enns. That the valley ofChamouni, the Valais, the Urseren Thal, and that of the Vorder Rhine really form part of one great fold is further shown by the presence of a belt of Jurassic strata nipped in, as it were, between the crystalline rocks.

This seems to throw light on the remarkable turns taken by the Rhone at Martigny and the Vorder Rhine at Chur, where they respectively quit the great longitudinal fold, and fall into secondary transverse valleys. The Rhone for the upper part of its course, as far as Martigny, runs in the great longitudinal fold of the Valais; at Martigny it falls into and adopts the transverse valley, which properly belongs to the Dranse; for the Dranse is probably an older river and ran in the present course even before the great fold of the Valais. This would seem to indicate that the Oberland range is not so old as the Pennine, and that its elevation was so gradual that the Dranse was able to wear away a passage as the ridge gradually rose. After leaving the Lake of Geneva the Rhone follows a course curving gradually to thesouth, until it reaches St. Genix, where it falls into and adopts a transverse valley which properly belongs to the little river Guiers; it subsequently joins the Ain and finally falls into the Saône. If these valleys were attributed to their older occupiers we should therefore confine the name of the Rhone to the portion of its course from the Rhone glacier to Martigny. From Martigny it occupies successively the valleys of the Dranse, Guiers, Ain, and Saône. In fact, the Saône receives the Ain, the Ain the Guiers, the Guiers the Dranse, and the Dranse the Rhone. This is not a mere question of names, but also one of antiquity. The Saône, for instance, flowed past Lyons to the Mediterranean for ages before it was joined by the Rhone. In our nomenclature, however, the Rhone has swallowed up the others. This is the more curious because of the three great rivers which unite to form the lower Rhone, namely, the Saône, the Doubs, and the Rhone itself, the Saône brings for a large part of the year the greatest volume of water, and the Doubs has the longest course. Other similar casesmight be mentioned. The Aar, for instance, is a somewhat larger river than the Rhine.

Fig. 41.—Diagram in illustration of Mountain structure.Fig. 41.—Diagram in illustration of Mountain structure.

But why should the rivers, after runningfor a certain distance in the direction of the main axis, so often break away into lateral valleys? If the elevation of a chain of mountains be due to the causes suggested in p. 214, it is evident, though, so far as I am aware, stress has not hitherto been laid upon this, that the compression and consequent folding of the strata (Fig. 41) would not be in the directionA Bonly, but also at right angles to it, in the directionA C, though the amount of folding might be much greater in one direction than in the other. Thus in the case of Switzerland, while the main folds run south-west by north-east, there would be others at right angles to the main axis. The complex structure of the Swiss mountains may be partly due to the coexistence of these two directions of pressure at right angles to one another. The presence of a fold so originating would often divert the river to a course more or less nearly at right angles to its original direction.

Switzerland, moreover, slopes northwards from the Alps, so that the lowest part of the great Swiss plain is that along the foot ofthe Jura. Hence the main drainage runs along the line from Yverdun to Neuchâtel, down the Zihl to Soleure, and then along the Aar to Waldshut: the Upper Aar, the Emmen, the Wiggern, the Suhr, the Wynen, the lower Reuss, the Sihl, and the Limmat, besides several smaller streams, running approximately parallel to one another north-north-east, and at angles to the main axis of elevation, and all joining the Aar from the south, while on the north it does not receive a single contributary of any importance.

On the south side of the Alps again we have the Dora Baltea, the Sesia, the Ticino, the Olonna, the Adda, the Adige, etc., all running south-south-east from the axis of elevation to the Po.

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