The Alpine Journal for November 1868 concludes with these words, “If anybody thinks that Alpine science has been already too thoroughly drilled into the public mind, we would refer him to a recent ridiculous letter which the editor of the Times did not think it beneath him to publish, and in which the writer said that a ‘puff of smoke,’ as it appeared on the mountain, ‘raised the cry that the Glacier des Pélérins had burst, carrying with it part of the moraine which kept it within bounds!’”
If any one had told the climbing world in those days that in 1891 the ordinary traveller would be nearly as ignorant of the behaviour of glaciers as was the Times correspondent referred to above, I fancy the prophet would have been received with derision. Such, however, I know to be the case; and only last year, while walking up Piz Languard with a party of friends, I was asked if the medial moraine of the Morteratsch glacier was a carriage road or only a bridle-path! This is my excuse for entering at some length into a subject which has been already written about in so able a manner and in much detail by Professors Tyndall, Forbes, Heim, Forel, and others.
Now, let me tell you something about those great icy masses which, under the name of glaciers, thrust their cold forms far below the region of perpetual snow, and in some cases, as, for instance, that of the Glacier des Bossons at Chamonix, even push down their frozen waves amongst the meadows and forests in the very trough of the valley.
I am constantly asked by those who are only acquainted with the lower end of the glaciers how it is that they are continually and rapidly melting at their lower extremity, and yet their general features are but slightly altered from year to year. The obvious answer is, that they are constantly replenished from above, and that glacier ice has formerly been snow, which, for a considerable period, has been subjected to enormous pressure. The common illustration of a snow-ball, squeezed in the hand till it becomes hard and icy, explains this transition of snow to ice in a manner easily understood by all, and if we remember that the warm hand, in addition to the pressure, also tends to produce the above result, we have a parallel to the heat of the sun acting on the cold, dry snow of the upper regions. Now, every one knows that when it rains in the valleys it snows on the mountains, and that even during the heat of summer it very seldom rains above a height of 11,000 to 12,000 feet. In consequence of this, the accumulation of snow on the higher peaks is very great, and the pressure which is exerted by its weight is enormous.
As a natural result, a portion of the ice-caps or snow-beds gravitates downwards, and where the upper snows are of great extent and the shape of the channel suitable, a large glacier is found, as is the case near Pontresina, where the huge Morteratsch glacier pursues its lengthy course, fed by the snows of the Bernina and Bellavista. The first to speak clearly and positively on the since well-proven theory that a glacier moves like a river was Monseigneur Rendu, a native of Savoy. “Between the Mer de Glace and a river there is a resemblance so complete, that it is impossible to find in the latter a circumstance which does not exist in the former,” he writes, and Professor Tyndall sets forth in an admirable manner the reason why a glacier moves more quickly in the centre than at the sides. I cannot do better than quote his own words.
“A cork, when cast upon a stream near its centre, will move more quickly than when thrown near the side, for the progress of the stream is retarded by its banks. As you and your guide stood together on the solid waves of that Amazon of ice, you were borne resistlessly along. You saw the boulders perched upon their frozen pedestals; these were the spoils of distant hills, quarried from summits far away, and floated to lower levels like timber blocks upon the Rhone. As you advanced towards the centre you were carried down the valley with an ever-augmenting velocity. You felt it not—he felt it not—still you were borne down with a velocity which, if continued, would amount to 1000 feet a year.”
Many glaciers descend in curves, pursuing a sinuous course towards the valley, and the convex side of the curve must, of course, hurry up very considerably in order to keep pace with the rest. Now, as the ice thus moves faster on the one side than on the other, the result is that the convex side is rent and torn asunder, and splits up into those cracks and chasms known as crevasses. Consequently, a glacier which flows downwards in a straight direction and at a gentle incline presents a comparatively unbroken surface, while a glacier which descends in leaps and bounds over a steep bed and dashes round sharp corners will exhibit all the features of an impassable ice-fall.
Striking examples of the former class of glaciers are the Aletsch glacier, the upper portion of the Gorner glacier, the Miage glacier, the Roseg glacier, the Pasterzen glacier, &c., and of the latter the Bies glacier, the Brenva glacier, the Géant glacier, the Pers glacier, and many others. The exact point at which the snow of the heights passes into glacier ice has never been definitely determined, but each winter’s snowfall is distinctly traceable by a band of differently-hued snow wherever above the snow-line a glacier is much split up.
High glacier-clad mountains are covered with what is known as névé—névé being the finely crystallised snow of the upper regions, which remains unmelted all the summer. The glacier ice which is formed by pressure of this névé is quite different to the ice which results from freezing water, and is found to consist of round crystals, varying in size from that of a hen’s egg to that of the head of a pin. Any observant person will have noticed the ice usually supplied at Swiss tables-d’hôtes, and the curious way in which it behaves as compared with ordinary ice; for while the latter melts uniformly from the outside, the former is honeycombed with air and water, and after a time its peculiar structure, composed of numerous particles, is noticeable. These crystals or particles are known as glacier granules or glacier corn.
The whiteness of a glacier, as compared with the blackness of a frozen lake, is a feature which I have known to puzzle many. It is simply owing to the presence of this glacier corn, which allows a great quantity of air to permeate the whole mass of the ice. The beautiful blue veined or ribboned structure, first observed by Forbes on the Unter-Aar glacier, is due to the absence of air-bubbles, and represents bruises in the ice where, by melting, strain, and pressure, certain parts have had the air driven out.
We will now notice several of the peculiarities which are conspicuous on the surface of one of these great rivers of ice. As we walk up from, say, the Morteratsch restaurant towards the glacier of that name, we must cross part of the stony and earthy mass known as the terminal moraine. Now the subject of moraines is a very large one, so much so, that we shall probably devote nearly the whole of a future chapter to it. For the present, we will merely walk over it, and get on to the very dirty ice of which the snout or lower end of the Morteratsch glacier is composed. As one of the party hews out the steps by which you mount, you have time to observe the ice crystals or glacier corn which we have already spoken of.
Before you have gone far on the level surface of the glacier, you will see several boulders which are resting on ice pedestals supported at some height. These are called glacier tables, and result from the presence of a block of stone which protects the ice beneath it from the heat of the sun, thus preventing it from melting. In consequence, while the glacier all round has been dissolving and sinking, the ice under these boulders has but slightly melted, and gradually a pillar of sometimes as much as four feet or more in height is formed under each erratic block. The sun is, of course, able to reach these ice pedestals more freely on the south than on the north side, and thus we observe that the boulder is not balanced evenly on the top, but always inclines downwards towards the south side; it thus has been known to render valuable aid to the mountaineer who has lost his way in a fog or in the dark without a compass on a glacier, as he can, by observing the position of a glacier table, easily inform himself of the direction in which he is walking. Small stones have a different effect, as they sink into the ice, leaving little holes. You will also probably notice a line of sand-covered mounds, about four or five feet high, and culminating in a sharp point or ridge. Scrape off a little of the sand and earth, and you will find that the mound is composed of ice, which looks quite black where you have uncovered it. The reason for the existence of these dirt cones is obvious; the sand has protected the ice, which has thus remained unmelted, and being heaped up thickly in the centre and thinning off towards the sides, has thus taken its sharply-pointed shape.
Continuing our walk up the glacier, we hear, gradually becoming louder and louder as we approach, the roar of falling water, and soon we reach a point where a bright, dancing stream leaps down a shaft in the ice and is lost to sight. Be careful how you approach this deep hole (or, as it is called, moulin), for one false step on your part would take you down far beyond all human aid. Various persons have endeavoured to gauge the thickness of a glacier at a given point by taking soundings down a moulin, and Agassiz found no bottom at 260 metres in one on the Unteraar glacier; he estimated the thickness of the ice to be 1509 feet near the Abschwung. On Piz Roseg, where the hanging glaciers end in abrupt ice-cliffs, a thickness of 250 feet has been observed. You are now at the foot of the lower ice-fall of the Morteratsch glacier. We will not go farther to-day, and we have already learnt how it is that the tottering ice masses and grim crevasses are formed. We know that the glacier on which we are standing is slowly moving downwards (by its weight, and by sliding in its bed, especially facilitated by its granular structure) at, roughly, the same rate as the hour-hand of an ordinary watch. It has been estimated—I believe by Mr. Tuckett—that a grain of snow would take 450 years to travel from the summit of the Jungfrau to the termination of the Aletsch glacier. A most painful illustration of the rate of motion of glaciers was furnished by the descent in the ice of the Glacier des Bossons of the bodies of Dr. Hamel’s three guides, who lost their lives on Mont Blanc in 1820, being carried down the Ancien Passage in an avalanche, and swept into the bergschrund at its base. On August 15, 1861, Ambrose Simond, a Chamonix guide, who was accompanying a party of tourists to the lower extremity of the Bossons glacier, noticed in one of the crevasses torn pieces of clothes and some human bones. He brushed off the sand with which they were covered, and brought them to Chamonix. Five men at once started on hearing what he had found, and they discovered other remains at a distance of some twelve or fifteen metres lower down. From that day, the glacier continued to give back the remains of what it had swallowed up forty-one years before, and what was found was beyond doubt the bodies and belongings of Dr. Hamel’s guides. All that they had carried with them, the scientific instruments, knapsacks, gloves, &c., were gradually set free from their icy fetters. A gauze veil came out untorn and not much faded; and the knapsack of Pierre Carrier contained a leg of mutton perfectly recognisable. More remarkable than anything else was the condition of a cork, which was not only still stained by the wine, but also possessed a perceptible odour of the contents of the bottle in which it had been fixed. (“Le Mont Blanc,” by Charles Durier.)
But it is time to descend, and in the next chapter I will make a few observations on moraines and the power of a glacier in planing down or removing whatever object it meets with; this power, as a matter of fact, being very much more limited than is popularly supposed.