John Tyndall

The Glaciers of the Alps


Скачать книгу

ice which I had noticed on the previous day were exclusively confined to this glacier, or to the space between the moraines a and b (Fig. 7), bending up so that the moraine a between the Glacier du Géant and the Glacier des Périades was tangent to them. At a good distance up the glacier I encountered a considerable stream rushing across it almost from side to side. I followed the rivulet, examining the sections which it exposed. At a certain point three other streams united, and formed at their place of confluence a small green lake. From this a rivulet rushed, which was joined by the stream whose track I had pursued, and at this place of junction a second green lake was formed, from which flowed a stream equal in volume to the sum of all the tributaries. It entered a crevasse, and took the bottom of the fissure for its bed. Standing at the entrance of the chasm, a low muffled thunder resounding through the valley attracted my attention. I followed the crevasse, which deepened and narrowed, and, by the blue light of the ice, could see the stream gambolling along its bottom, and flashing as it jumped over the ledges which it encountered in its way. The fissure at length came to an end: placing a foot on each side of it, and withholding the stronger light from my eyes, I looked down between its shining walls, and saw the stream plunge into a shaft which carried it to the bottom of the glacier.

      Slowly, and in zigzag fashion, as the crevasses demanded, I continued to ascend, sometimes climbing vast humps of ice from which good views of the surrounding glacier were obtained; sometimes hidden in the hollows between the humps, in which also green glacier tarns were often formed, very lonely and very beautiful.

      A LAKE SET FREE. 1857.

      While standing beside one of these, and watching the moving clouds which it faithfully mirrored, I heard the sound of what appeared to be a descending avalanche, but the time of its continuance surprised me. Looking through my opera-glass in the direction of the sound, I saw issuing from the end of a secondary glacier on the Tacul side a torrent of what appeared to me to be stones and mud. I could see the stones and finer débris jumping down the declivities, and shaping themselves into singular cascades. The noise continued for a quarter of an hour, after which the torrent rapidly diminished, until, at length, the ordinary little stream due to the melting of the glacier alone remained. A subglacial lake had burst its boundary, and carried along with it in its rush downwards the débris which it met with in its course.

      IMPRESSIVE SCENE. 1857.

      In some places I found the crevasses difficult, the ice being split in a very singular manner. Vast plates of it not more than a foot in thickness were sometimes detached from the sides of the crevasses, and stood alone. I was now approaching the base of the séracs, and the glacier around me still retained a portion of the turbulence of the cascade. I halted at times amid the ruin and confusion, and examined with my glass the cascade itself. It was a wild and wonderful scene, suggesting throes of spasmodic energy, though, in reality, all its dislocation had been slowly and gradually produced. True, the stratified blocks which here and there cumbered the terraces suggested débacles, but these were local and partial, and did not affect the general question. There is scarcely a case of geological disturbance which could not be matched with its analogue upon the glaciers—contortions, faults, fissures, joints, and dislocations—but in the case of the ice we can prove the effects to be due to slowly-acting causes; how reasonable is it then to ascribe to the operation of similar causes, which have had an incomparably longer time to work, many geological effects which at first sight might suggest sudden convulsion!

      Wandering slowly upwards, successive points of attraction drawing me almost unconsciously on, I found myself as the day was declining deep in the entanglements of the ice. A shower commenced, and a splendid rainbow threw an oblique arch across the glacier. I was quite alone; the scene was exceedingly impressive, and the possibility of difficulties on which I had not calculated intervening between me and the lower glacier, gave a tinge of anxiety to my position. I turned towards home; crossed some bosses of ice and rounded others; I followed the tracks of streams which were very irregular on this portion of the glacier, bending hither and thither, rushing through deep-cut channels, falling in cascades and expanding here and there to deep green lakes; they often plunged into the depths of the ice, flowed under it with hollow gurgle, and reappeared at some distant point. I threaded my way cautiously amid systems of crevasses, scattering with my axe, to secure a footing, the rotten ice of the sharper crests, which fell with a ringing sound into the chasms at either side. Strange subglacial noises were sometimes heard, as if caverns existed underneath, into which blocks of ice fell at intervals, transmitting the shock of their fall with a dull boom to the surface of the glacier. By the steady surmounting of difficulties one after another, I at length placed them all behind me, and afterwards hastened swiftly along the glacier to my mountain home.

      CHAMOUNI RULES. 1857.

      On the 30th incessant rain confined us to indoor work; on the 31st we determined the velocity with which the glacier is forced through the entrance of the trunk valley at Trélaporte, and also the motion of the Grand Moulin. We also determined both the velocity and the width of the Glacier du Géant. The 1st of August was spent by me at the cascade of the Talèfre, examining the structure, crumpling, and scaling off of the ice. Finding that the rules at Chamouni put an unpleasant limit to my demands on my guide Simond, I visited the Guide Chef on the 2nd of August, and explained to him the object of my expedition, pointing out the inconvenience which a rigid application of the rules made for tourists would impose upon me. He had then the good sense to acknowledge the reasonableness of my remarks, and to grant me the liberty I requested. The 3rd of August was employed in determining the velocity and width of the Glacier de Léchaud, and in observations on the lamination of the glacier.

      THE JARDIN. 1857.

       (9.)

       Table of Contents

      A RESERVOIR OF ICE. 1857.

      On the 4th of August, with a view of commencing a series of observations on the inclinations of the Mer de Glace and its tributaries, we had our theodolite transported to the Jardin, which, as is well known, lies like an island in the middle of the Glacier du Talèfre. We reached the place by the usual route, and found some tourists reposing on the soft green sward which covers the lower portion, and to which, and the flowers which spangle it, the place owes its name. Towards the summit of the Jardin, a rock jutted forward, apparently the very apex of the place, or at least hiding by its prominence everything that might exist behind it; leaving our guide with the instrument, we aimed at this, and soon left the grass and flowers behind us. Stepping amid broken fragments of rock, along slopes of granite, with fat felspar crystals which gave the boots a hold, and crossing at intervals patches of snow, which continued still to challenge the summer heat, I at length found myself upon the peak referred to; and, although it was not the highest, the unimpeded view which it commanded induced me to get astride it. The Jardin was completely encircled by the ice of the glacier, and this was held in a mountain basin, which was bounded all round by a grand and cliffy rim. The outline of the dark brown crags—a deeply serrated and irregular line—was forcibly drawn against the blue heaven, and still more strongly against some white and fleecy clouds which lay here and there behind it; while detached spears and pillars of rock, sculptured by frost and lightning, stood like a kind of defaced statuary along the ridge. All round the basin the snow reared itself like a buttress against the precipitous cliffs, being streaked and fluted by the descent of blocks from the summits. This mighty tub is the collector of one of the tributaries of the Mer de Glace. According to Professor Forbes, its greatest diameter is 4200 yards, and out of it the half-formed ice is squeezed through a precipitous gorge about 700 yards wide, forming there the ice cascade of the Talèfre. Bounded on one side by the Grande Jorasse, and on the other by Mont Mallet, the principal tributary of the Glacier de Léchaud lay white and pure upon the mountain slope. Round further to the right we had the vast plateau whence the Glacier du Géant is fed, fenced on the left by the Aiguille du Géant and the Aiguille Noire, and on the right