The Beauties of Nature, and the Wonders of the World We Live In Part 14

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

Below the _neve_ lies 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 blue cavern, though in others the end of the glacier is enc.u.mbered and concealed by earth and stones.

[Ill.u.s.tration: Fig. 24.--Upper Valley of St. Gotthard.]

The uppermost Alpine valleys are perhaps generally, though by no means always, a little 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 ma.s.ses, 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 chalets 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 central cultivated 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 rus.h.i.+ng 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.

[Ill.u.s.tration: 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.

[Ill.u.s.tration: 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.

[Ill.u.s.tration: 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.

[Ill.u.s.tration: 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 quant.i.ties 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.

[Ill.u.s.tration: 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.

[Ill.u.s.tration: Fig. 30.]

[Ill.u.s.tration: VIEW IN THE VALAIS BELOW ST. MAURICE. _To face page 266._]

[Ill.u.s.tration: 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, each marking the place where a stream falls into the lake.

[Ill.u.s.tration: 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.

[Ill.u.s.tration: Fig. 33.--Sh.o.r.e 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]

[Ill.u.s.tration: 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 gra.s.ses, 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 d.y.k.es, 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.

[Ill.u.s.tration: Fig. 34.--View in the district of the Broads, Norfolk.]

At present these rivers are restrained in their courses by banks; when left free they are 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 [Greek: Delta], 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.

[Ill.u.s.tration: 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 s.h.i.+ps up the river live in frail houses resting on planks, and kept in place by anchors. Still further, and the 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 separate them 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.

[Ill.u.s.tration: Fig. 36.]

FOOTNOTES:

[48] Leyden.

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

[50] F. Davors.

[51] Ruskin.

CHAPTER VIII

RIVERS AND LAKES

ON THE DIRECTIONS OF RIVERS

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.