"OLD as the hills" is not a comparison that would be considered apt if invented to-day, for we now know that, geologically speaking, the greatest mountain ranges are of recent elevation, and that even low hills are seldom of great antiquity. It was not till men became climbers, and so grew to have an intimate acquaintance with mountains in detail, that a recognition of the rapid degradation which all mountains are suffering was clearly obtained. To look at the Matterhorn from below is to behold an apparently everlasting tower, yet its base is strewn with ruins, and its flanks are continuously swept by falling masses of rock.

The realisation of this different point of view, which we must presently discuss in more detail, forms a clear mark of division between the attitude towards mountains, of men in the pre-scientific age and to-day. Our forefathers naturally regarded the hills as eternal and everlasting. They defined the beginning of things in such phrases as "Before the mountains were brought forth." The tops of peaks, actually their newest feature, were hoary-headed to them. This was indeed partly due to their limited idea of the stretch of time into the past. Six thousand years, which to us seems but a day, was an eternity to them. Of course six thousand years is a brief period in the life of a mountain. Judged by such a standard it may be called eternal, and that was the kind of meaning they attached to the word. Mountains have grown young as our notions of time past have extended. If we could lengthen our time-span, the interval of time (about one-tenth of a second) of which we are simultaneously conscious, if we could extend it to years instead of a fraction of a second, we should actually see the mountains changing. In a sense that is what we have imaginatively accomplished.

Pre-scientific man possessed no such power. Dwellers in mountain countries beheld the peaks apparently ever the same. Each summer, as it stripped away part of the winter accumulation of snow, revealed the same apparently unaltering features. They knew nothing of the movement of glaciers. They regarded snow-mountains as accumulations piled up continuously from the beginning of the world and destined to go on increasing till the end. I remember reading in the comparatively recent book of travel written by an Anglo-Indian, how he went up some Himalayan valley and came to the glacier at the head of it. He attempted to go no further. He conceived himself to have reached the limit of possible advance. He mounted some way up the hillside and looked along towards the head of the valley; all was ice—an accumulation fallen from the cliffs on either hand for thousands of years and some day destined to fill the trough to the brim—such was his notion of the thing he was looking at.

Changeless, eternal, forbidding, still, silent, and horrible—thus the snowy ranges appeared to the pre-scientific gaze. To us they seem the very reverse. We know them to be ceaselessly changing, of relatively short persistence, the theatre of movements of all kinds both violent and slow—not places of death by any means, but the home of an active, a beneficent, and a formative life—not regions cut off and unrelated to the lowlands and habitable world, but the very parent of such, the laboratory where soil is made, and the head of water collected that distributes it below; the counterbalance of the denuding forces that would level the earth with the ocean; regions beneficent as they are beautiful, and as necessary to the well-being of the habitable world as is the richest and most fertile plain.

He that would know mountains and mountain regions aright must know them as the theatre of change, the domain of action. He must not merely look upon peaks as they are, but must conceive of them as they have been and will be. As this kind of knowledge grows and becomes instinctive within him, it will alter his attitude towards Alpine panoramas and broaden his grasp of the significance of mountain physiognomy.

Let us briefly consider the stages of formation and decay of a single group of mountains, not volcanic. If we go back to the very start, we may imagine their future site occupied by a plain. The slow cooling and consequent shrinking of the world involves the wrinkling of its surface, and the position of the wrinkles is determined by a variety of forces, as yet little understood, with which we need not concern ourselves. Suffice it to assume that our plain occupies the position of the next coming group of wrinkles. A single range or line of mountains hardly exists in the world outside of the commonplace cartographer's mind. Old-fashioned maps used to represent mountains by a kind of caterpillar meandering about on them, and thus gave currency to the notion that mountains are generally arranged along a single line—a notion, by the by, that (in the minds of politicians negotiating boundary treaties) has been prolific in costly disputes and misunderstandings.[2] Mountains generally exist in rows of more or less parallel ranges intricately jointed together, and they do so because, when the wrinkling that caused them began, it did not begin with a single wrinkle, but with a row of wrinkles, such as a soft tablecloth makes on a smooth table when parts of it are moved toward one another.

[2] Witness the Argentine and Alaska boundary disputes.

Thus the first sign of a mountain range will be a series of undulations upon the surface of the supposed plain. These undulations will be roughly parallel to one another. We call the direction of their parallelism the strike of the ranges. From the moment the wrinkling movement begins, a set of forces is put in operation tending to level the wrinkles and fill up the hollows or valleys between them. These are the forces of denudation. People often vaguely speak as though mountains were first elevated to their full height and then only began to be pulled down; but of course the process of mountain sculpture is due to the simultaneous operation of the elevating and destructive forces. Every mountain is being pulled down in the very process of its elevation. It grows only because it is elevated faster than the destructive forces avail to level it. For all we yet know, some of the mountain ranges which seem most rapidly disintegrating may, in fact, still be growing. No one has yet divided the mountain ranges of the world into those which have not yet reached and those which have passed their maturity. When that has been done we shall doubtless find some clearly marked difference in aspect between them which now we do not know enough to recognise. The visible difference once discovered, the two groups will raise different kinds of emotion in the man who sees them. He will note the aspect of growth in one set and of decay in the other, and will be correspondingly affected, as we all now are by the young leaves and buds of spring and the fruits and faded foliage of autumn. Sad folk will love the fading and sanguine folk the growing hills. There will arise a new subject for poets and a new group of similes for preachers and moralists. In this way also science enlarges the material of art.

But we must return to our nascent mountain group, as yet a mere series of parallel wrinklings, higher here, lower there, with lines of depression between them. Rain falling will need to drain away, and in doing so will form pools in hollows, and will run along the furrows till it reaches the open country and can turn away. Thus the first streams of a nascent group of mountains follow and do not flow across the strike. Only the rivulets that actually flow down the slopes will flow in a direction perpendicular to the strike, and will be tributaries to the main lines of drainage that flow along the strike.

The mountains are rising steadily as the millenniums of years pass on. The rain keeps falling on them, and as they grow higher the snows of winter first, and later of all the year, whiten their summits and gradually descend upon their slopes as the summits reach higher and higher aloft. If the rain always fell uniformly over the whole area, and if the ranges were of rock, homogeneous like a great lump of plaster, equally strong in every direction—if such were the case, each range would remain approximately symmetrical on both sides, and the crest of it would lie evenly between its two flanking troughs. But that is never the case. The rain-bringing winds are sure to come more frequently from one side of the mountain area than from the other. The wet quarter will be the east or the west or the south-west, as the case may be, and more moisture will be precipitated and consequently more denudation effected by it on one side of the ridges than on the other, with important sculpturing results as we shall presently observe.

We may best regard the rising mountain area as a plateau with a wrinkled top, such a plateau as Tibet, for example. As time advances the plateau will present ever loftier walls to the outside world, but the undulations within will not greatly develop by any directly wrinkling process. It is not the wrinkling that splits the plateau up into ranges, but quite other forces. All that the wrinkling does is to give to those forces their first direction. The interior of Tibet shows us what, but for these other forces, a great mountain region would be like. It would be traversed from end to end by low and roughly parallel ridges, separated from one another by shallow valleys raised high aloft on the great plateau-pedestal. In the shallow valleys there would lie many lakes, some having no outlets, others drained by slow streams flowing along the strike of the ranges, and fed by driblets from the slopes of the flanking hills.

But at the ends and around the periphery of the plateau generally a different condition of things will be found. Let us regard the ends first. The slow flowing rivers of the plateau as they reach its extremity will become swift, where they plunge down to the plain. In proportion to their swiftness is the speed with which they cut down their beds into the mass of the plateau-pedestal. If the end of the plateau were a cliff, the rivers would tumble over it in waterfalls, and these would cut their way back and thus dig out caÑons in place of the shallow valleys of the original wrinkling. In any case a similar result will be arrived at, and the plateau will be more and more cut down into deep valleys with high ridges between. What were originally small wrinkles above the mean level of the plateau and slight depressions beneath it will be changed by denudation into high mountains and deep valleys, their scale being determined by the amount of general elevation of the plateau above the low-lying country. As the general elevating process goes on, so does the excavation. The deep valleys will be formed first at the edge of the plateau. They will work back into its heart in process of time. The original Tibetan plateau is now greatly reduced, and only the remaining middle part of it preserves any resemblance to its primary surface-form. As you go eastward or westward from that central portion you come into ever deepening valleys and ever relatively higher peaks, measured from the neighbouring valley floor.

Thus far we have only spoken of the natural development of the strike rivers, those original lines of flow that follow the direction of the ranges. We must now observe how their course is affected by the development of the tributary streams that flow down the slopes of the ridges approximately at right angles to the strike. In the case of the Himalayas the rains come from southerly quarters. The damp air-current drifts against and over the plateau from that direction. Contact with the elevations against which it drifts causes the rains to fall. As the damp current flows further north it becomes continually dryer, so that less and less rain falls. Thus denudation is most energetic on the southern slopes. As the plateau rises its southern edge (to consider that alone for a moment) is most vigorously cut into by the water pouring down that face and forming gullies, which continuously tend to deepen and to cut back into the mass of the plateau. The process has only to go forward long enough, for the most energetic of these side-streams to eat its way back, right through the outermost wrinkle of the plateau, till it taps the first or southernmost of the strike rivers. From that moment the course of the strike river is changed, and instead of flowing away along its original valley, it turns at right angles and flows out through the gully cut by the side-stream, which thus becomes the main river. The next wrinkle is in turn attacked by the side-streams flowing down its south slope and in turn cut through, so that the second strike river becomes thus tributary to the first. And so the process continues.

Such is the history of the formation of a great river like the Indus. It is filled by the robbed waters of countless smaller rivers, one by one drawn within its drainage area by the action of side-streams cutting through intervening ridges. All these rivers and their tributaries go on cutting their way back with ever-increasing vigour as the trunk outlet is lowered by their united volume. This is the process whereby an original plateau is sculptured into a maze of ridges and valleys. The towering heights we behold were never elevated in isolated magnificence. A different thrust did not send up the Matterhorn, the Weisshorn, and Monte Rosa, but all the neighbourhood was elevated by one great heaving. To begin with, some lines of elevation were a little higher than others, and they determined the position of principal peaks and ridges; but as the mass was elevated the hollows were engraved by the burin of flowing water. The higher the mass was raised the deeper the hollows were impressed and the wider became their opening, for the self-same forces operate on every slope and continually eat it away and open side-valleys and subsidiary side-valleys into them. These forces operating on both sides of every ridge rapidly pull down its crest and ultimately round it off and reduce it lower and lower continually, so that it is only a question of time for the biggest mountain mass to be lowered to the level of the plains around it.

Running water is not the only agent that has to be considered. Even more energetic agents act in the higher regions of frost. There the snow that is melted by the sun (whose dissolving power is as operative in the regions so-called of perpetual snow as it is below) percolates into the crevices of the rocks and finds out all their weak places. At night this water freezes, and in freezing expands, thus acting like a wedge and splitting the rock it has penetrated. Next time the sun shines the pieces thus split off may fall. Sooner or later, after repeated operations of the wedge, they must fall, and a new surface of rock will be uncovered to be split and shivered in its turn. The rocks that fall tumble ultimately on to the snow-fields that spread over the high open spaces, where they are taken charge of by the great carrying agents of the heights—the glaciers. The higher a peak is, relatively to its neighbours, the more rapidly will frost attack it, and the more energetic will be the destruction wrought upon it. I have heard it estimated, or perhaps only guessed, that 1000 tons of rock fall daily from the upper portion of the Matterhorn's rock-pyramid. The great peaks of the Himalaya are falling yet more rapidly to pieces.

But what in this relation is the action of the glaciers? At one time they were regarded as a great abrading agency. It was thought that the high valleys were fashioned out by them. Later it was concluded that their hollowing action was a negligible quantity. The general belief now is that it is not considerable. Whatever may be the action of glaciers upon their beds, it is at all events a small matter compared with their action as transporting agents. Glaciers are not hoary accumulations of snow, collected in hollow places since the beginning of the world, as our forefathers supposed, but flowing streams of ice, whose rate of movement varies with the slope, the latitude, the mean temperature, and other factors of their situation. The snow that falls at high elevations lies in great masses where it finds lodgment, or falls to such places from the steep rocks which are unable to give it steady support. By these means it falls and drifts together into those great upper reservoirs we call the snow-fields—resplendent areas of purest white, so toilsome to cross when the sun shines hotly upon them, and so incomparably beautiful to look upon. Here by melting of the surface, percolation into the body of the snow-field, and freezing there, and by the pressure of the ever-increasing accumulation of snow, the substance is gradually changed into granulated ice, and the ice thus formed slowly moves down-hill. The various neighbouring streams of ice flow and unite together, and thus, reaching lower and lower levels and continually melting, they come to a line where the annual increment of snow is equal in amount to the depth of snow annually melted. This is called the snow-line. Still downward flows the mass, and now the amount melted becomes greater than the amount annually received. The thickness of the ice steadily diminishes till at last the total arrival melts and the glacier ends in a so-called snout.

The great importance of glaciers in mountain formation is the part they play as carrying agents. There is practically no limit to the weight of rock they will bear down with them in their steady uninterrupted flow. Whatever falls upon the glacier at any part of its course is carried down by it and ultimately dumped off its sides or end. A stone that falls on the highest rim of the snowfield will presently be covered up by newly-fallen snow and will be carried down at, or close to, the floor of the glacier, where it will either be ground to powder or will not emerge till it is melted out at the end of the glacier's snout. A stone that plunges in a crevasse to the bottom of the glacier will have similar experiences. Stones that tumble on to the glacier surface further down will not be so deeply covered by annual accumulations of snow, and will therefore sooner emerge again on to the surface by the melting away of the accumulation above them. Stones that fall on to the glacier below the snow-line will not be covered up at all, but will simply be carried down on the surface.

The visible collections of stone rubbish carried by a glacier are called its moraines. As the surface of a glacier tends to become convex the moraine-stuff tends to be rolled off towards the sides, where it forms the right and left lateral moraines. Where two glaciers flow together and unite, the right lateral moraine of the one and the left of the other will join and be carried down as a medial moraine on the surface of the united glacier. Such medial moraines may be observed in considerable numbers flowing down, side by side, on glaciers formed by the union of a number of higher tributaries. First comers to the Alps, beholding them from a distance, or seeing them in photographs, sometimes have thought they were cart-ruts, thus showing how false a scale of size their unaccustomed vision applies to mountain views.

A given kind of rock subjected to the action of frost and the other disintegrating forces operative at high levels, usually breaks up into debris of a roughly uniform average size. There will, of course, be some large masses and a lot of dust and gravel, but the average lump will be fairly uniform. A climber in a given district comes to know what to expect on a moraine, and he will immediately notice if the average size of the debris is much larger or smaller than usual. Thus, when he sees a debris-slope or a moraine from a distance, he is instinctively conscious that its granulated aspect represents great blocks of rock. That gives him a roughly correct scale for the view. The lowlander, who has never been in contact with a moraine, has no such sense, and can imagine that the brown streak he sees a few miles away is, as it looks to be, a mere line of dust. It was through the aspect of the moraines and debris-slopes that I first obtained an approach to a direct visual understanding of the vaster scale of the Himalayas than that of the Alps.

A cliff below the snowy regions, if it does not rise out of the sea, is protected at its base by the debris fallen from it. What tumbles from above piles up below, and keeps the foot of the cliff from being eaten away. But a cliff or slope of rock rising out of a glacier or snow-field is deprived of such protection. All the stones that fall from it are carried away by the ice, so that the surface of the whole cliff keeps on peeling off, and that face of the mountain is gradually planed away. Where a great glacier bay reaches into the mountains this action may be very energetic. The whole surrounding cirque is constantly eaten at and continually extends its inner circumference. In some regions this action is more rapid than in others. Where, as in the tropics, the heat is great by day and the frost at high altitudes bitter by night, destruction goes quickly forward, and the mountains are vigorously reduced. Weak points in the rocky structure are soon found out. The range itself will be penetrated. A pass thus formed tends to be continuously lowered. In the neighbourhood of the greatest altitudes the destruction is of course most vigorous. This is the reason why, in so many places, alike in the Himalayas and the Andes, cross-cutting rivers find their way through a range by a gorge that passes quite near a culminating peak. The great Indus gorge below Nanga Parbat is the most notable instance I can recall.

We have thus, in the briefest possible manner, sketched out how some of the chief sculpturing forces operate to form mountains. I have not attempted to go into detail or to explain the various corrections and modifications that have to be applied to make the simple outline correspond with facts. Some valleys are actual depressions formed by the caving in of the earth along a line of weakness. Every mountain region contains examples of such hollows. Now and again by some complication or intersection of the wrinkling process a small area may be forced up considerably higher than the surrounding elevation and thus the mass provided for an exceptionally high peak. Volcanic peaks also remain to be considered, and have been excluded from the foregoing brief survey.

In the main, however, the statement is correct that the mountains of a region are produced by the sculpturing into ridges and subsidiary ridges of a great and slowly elevated mass. What begins as a growing plateau, passes through the stage of rocky and snowy ranges, becomes later on an area of undulating country, and if time sufficed would ultimately flatten out once more into a plain. Between the first stage and the last the sculpturing operations of nature pass through many phases. In the beginning, when the area has only just begun to rise from the level, those forces operate gently. Slopes are slight and streams flow easily down them. When the mountains have been roughly blocked out and the valleys precipitously deepened, the region enters into the dramatic stage of its history. The peaks are at their highest, the valleys at their deepest relatively to the heights. Cliffs are boldest, needles sharpest, torrents most voluminous and rapid. Now is the time when great mountain-falls most frequently occur. The rocks do not merely crumble away stone by stone, but huge masses are undermined and fall with gigantic crash and violence into the valleys, temporarily damming them across and forming lakes, which presently burst, and pour an incredible volume of water in destructive flood down the narrow and winding valley below. The flood transports and grinds up great quantities of rock and carries the material afar, for hundreds of miles perhaps, before the plain is reached and the mud deposited upon it.

In the theatrical stage mud avalanches are likewise common. To produce them there must be a great supply of loose debris on steep rocks at a high level and much rapidly melting snow about them, whose water drains into gullies and unites in larger gullies, all with banks of rotten and crumbling rock. On a suitable day in early summer, when the sky is clear and the sun hot, the stones will fall in such numbers that they will plug some gully and dam back the water. It will collect and burst the dam, and a flow of stones, dust, and water will begin. At other neighbouring spots the same thing will happen, and the elements of the avalanche will flow together, block a larger gully, and presently burst that block also. So it will go on till a great mass of mud, water, and rocks collects somewhere and finally bursts loose in an avalanche which sweeps all before it.

Such an avalanche I saw from close at hand on 8th July 1892, in the mountains of Nagar. We were walking up the right bank of a great glacier river, and were forced at intervals to cross its tributaries which came rushing down the hillside on our left. Approaching the mouth of one of these side gullies we heard a noise like thunder and beheld a vast black wave bulging down it. It passed before we arrived and there was silence for a few minutes. Presently the sounds of another were heard aloft, and it soon heaved into view—a terrific sight. The weight of the mud rolled masses of rock down the gully, turning them over and over like so many pebbles. They restrained the muddy torrent and kept it moving slowly with accumulating volume. Each big rock in the vanguard of the avalanche weighed many tons; some were about 10-foot cubes. The stuff behind them filled the gully some 15 feet deep by 40 wide. The thing travelled perhaps at the rate of seven miles an hour. Sometimes a bigger rock than usual barred the way till the mud, piling up behind it, swept it on. The avalanche ate into the sides of the gully and carried away huge undermined masses that fell into it. We saw three enormous avalanches of this sort pass down the same gully in rapid succession, and, after we had gone by, others followed. All the neighbouring similar gullies discharged such groups of mud avalanches during that period of the year. They are one of the chief agents used by nature to pull down mountains during this, the dramatic stage of their existence. The roaring torrential river below carries off the mud and receives the boulders in its bed, where they are rolled along and in time ground to powder.

Mud avalanches are rare now in the Alps, and are only caused by some exceptional event, such as the bursting of a glacier lake. Once they were common. Mountain-falls of any great size are also much rarer in the Alps now than they were formerly or than they are in some Himalayan regions. Alps and Andes have passed beyond the culmination of their dramatic stage. The mountains of Hunza, Nagar, and North Kashmir generally, are in the midst of theirs.

A mountaineer who has acquired a knowledge of how mountains are made, who has seen in action the forces I have briefly described, who has climbed among mountains in sunshine and storm, in heat and frost, who has spent nights on their cold crests, who knows how and where avalanches of snow, ice, and rock are likely to fall and has a realising sense of their force, their frequency, and their mass: a mountaineer who has attained by long experience a knowledge of the ways and action of glaciers, who can as it were feel their weight and momentum, in whose mind, when he looks at them, they are felt to be moving and vigorous agents, who sees the lines of motion upon them, their swing round corners, their energy in mid course, their feebleness at the snout:—such a man can look abroad over a mountain panorama with an understanding, a sense of the significance of what he beholds, which, far from detracting from its aspect of beauty, adds greatly to it.

To him a mountain area is no confused labyrinth of valleys and tangle of ridges, but the orderly and logical expression of a number of forces, and of forces that are still operative. To him what he beholds is not a painting on the wall, finished and done once and for ever, but, as it were, a scene in a play—a scene to which others have led up, and after which others will follow, all linked together and arising one out of another in unavoidable and necessary sequence. He perceives the arrangement of the peaks to be as logical as that of the men in a regiment on parade. Each stands in its own proper place, buttressed, and founded upon a broad and sufficient base. Its drapery of snow is not a kind of fortuitous whitewashing, splashed on anyhow by the whim of a storm. It is a vital part of the peak to which it adheres, owing all its forms to the modelling of that peak—here lying in deep and almost level snow-fields where broad hollows exist beneath it; there breaking into a mass of towering sÉracs where it is forced to fall over a step in its bed; there again reuniting in a smoothly surfaced area where the bed is once more relatively smooth; yet again opening a system of crevasses where its substance is torn asunder by unequal rates of flow.

LOOKING OVER LUCERNE FROM THE DREI LINDEN

The Towers of the Musegg in the middle distance.