« AnteriorContinuar »
the scenery, to St. Oyen,, where the Piedmontese custom, house is placed, and where the passports are examined. These require great regularity, or the permission to pass is withheld. Beyond St. Oyen, al Etroubles, another examination takes place. The Piedmontese officers are usually very courteous, an advantage, which the good temper of the traveller is sure to obtain.
At Etroubles, the St. Bernard branch of the Buttier is. crossed, and the road descends to the village of Gignod, where the vegetation begins to luxuriate, and the Italian side of the mountain is felt and seen. Here there is a fine peep into the Val Pellina. From Gignod to the city of Aosta, the richness of the scenery is constantly increasing. Trellised vines and Indian corn mark the approach to the Val d'Aosta ; and the first view of the city and the valley, in the descent from the St Bernard, where the back ground is filled with the magnificent forms and snowy summits of the mountains above the Val de Cogne; is perhaps, one of the finest in the Alps.
GLACIERS OF CHARMONTANE, THE COL DE FENÊTRE AND
"Vast blocks of stone,” says Brockedon, in his Excursions in the Alps, “which were driven and deposited there by the force of the waters, now strew the valley; and sand and pebbles present an arid surface, where rich pasturages were seen
before the catastrophe. The quantity and violence of the water suddenly disengaged, and the velocity of its descent, presented a force which the mind may calculate, but cannot conceive.
“ In the accounts which have been given of this event, the object of the writers has been merely to deseribe the catastrophe, and the extent of its injuries, but in reading the account of M. Escher de Linth, published in the Bib. Univ. de Genève, Sci. et Arts, tom, viii. p. 291, I was most forcibly struck with the unparalleled heroism of the brave mer who endeavoured to avert the evil, by opening a channel for the waters, which had, by their accuinulation, become a source of terror to the inhabitants of these valleys.
“In the spring of 1818, the people of the valley of Bagnes became alarmed on observing the low state of the waters of the Drance, at a season when the melting of the snows usually enlarged the torrent; and this aların was increased by the records of similar appearances before the dreadful inundation of 1595, which was then occasioned by the accumulation of the waters behind the débris of a glacier that formed a dam, which remained until the pressure of the water burst the dike, and it rushed through the valley, leaving desolation in its course.
“ In April 1818, some persons went up the valley to ascertain the cause of the deficiency of water, and they discovered that vast masses of the glaciers of Getroz, and avalanches of snow, had fallen into a narrow part of the valley, between Mont Pleureur and Mont Mauvoisin, and formed a dike of ice and snow 600 feet wide and 400 feet high, on a base of 3000 feet, behind which the waters of the Drance had accumulated, and formed a lake above 7000 feet long. M. Venetz, the engineer of the Valais, was consulted, and he immediately decided upon cutting a gallery through this barrier of ice, 60 feet above the level of the water at the time of commencing, and where the dike was 600 feet thick. He calculated upon making a tunnel through this mass before the water should have risen 60 feet higher in the lake. On the 10th of May, the work was begun by gangs of fifty men, who relieved each other, and worked, without intermission, day and night, with inconceivable courage and perseverance, neither deterred by the daily occurring danger from the falling of fresh masses of the glacier, nor by the rapid increase of the water in the lake, which rose 62 feet in 34 days-on an average nearly two feet each day; but it once rose five feet in one day, and threatened each moment to burst the dike by its increasing pressure; or, rising in a more rapid proportion than the men could proceed with their work, render their efforts abortive, by rising above them. Sometimes
dreadful noises were heard, as the pressure of the water detached masses of ice from the bottom, which, floating, presented so much of their bulk above the water as led to the belief that some of them were 70 feet thick. The men persevered in their fearsul duty without any serious accident, and though suffering severely from cold and wet, and surrounded by dangers which cannot be justly described, by the 4th of June they had accomplished an opening 600 feet long; but having begun their work on both sides of the dike at the same time, the place where they ought to have met was twenty feet lower on one side of the lake than on the other : it was fortunate that latterly the increase ofthe perpendicular height of the water was less, owing to the extension of its surface. They proceeded to level the highest side of the tunnel, and completed it just before the water reached them. On the evening of the 13th the water began to flow. At first, the opening was not large enough to carry of the supplies of water which the lake received, and it rose two feet above the tunnel; but this soon enlarged from the action of the water, as it melted the floor of the gallery, and the torrent rushed through. In thirty-two hours the lake sunk ten feet, and during the following iwenty-four hours twenty feet more; in a few days it would have been emptied; for the floor melting, and being driven off as the water escaped, kept itself below the level of the water within'; but the cataract which issued from the gallery melted, and broke up also a large portion of the base of the dike which had served as its buttrees': its resistance decreased faster than the pressure of the lake lessened, and at four o'clock in the afternoon of the 16th of June the dike burst, and in half an hour the water escaped through the breach, and left the lake empty.
“The greatest accumulation of water had been 800,000,000 of cubic feet; the tunnel, before the disruption, had carried off nearly 330,000,000-Escher says, 270,000,000; but he neglected to add 60,000,000 which 'flowed into the lake in three days. In half an hour, 530,000,000 cubic feet of water passed through the breach, or 300,000 feet per second; which is five times greater in quantity than the waters of the Rhine at Basle, where it is 1300 English feet wide.
In one hour and a half the water reached Martigny, a distance of eight leagues. Through the first 70,000 feet it passed with the velocity of thirty-three fcet per second-four or five times faster than the most rapid river known; yet it was charged with ice, rocks, earth, trees, bouses, cattle, and men; thirtyfour persons were lost, 400 cottages swept away, and the damage done in the two hours of its desolating power exceed: ed a million of Swiss livres, All the people of the valley had been cautioned against the danger of a sudden irruption ;
yet it was fatal to so many. All the bridges in its course were swept away, and among them the bridge of Mauvoisin, which was elevated 90 feet above the ordinary height of the Drance. If the dike bad remained untouched, and it could have endured the pressure until the lake had reached the level of its lop, a volume of 1,700,000,000 cubic feet of water would have been accumulated there, and a devastation much more fatal and extensive must have been the consequence. From this greater danger the people of the valley of the Drance were preserved by the heroism and devotion of the brave men who effected the formation of the gallery in the dike, under the direction of M. Venetz. I know no instance on record of courage equal to this : their risk of life was not for fame or for riches-they had not the usual excitements to personal risk, in a world's applause or gazetted promotion,their devoted courage was to save the lives and property of their fellow-men, not to destroy them. They steadily and heroically persevered in their labours, amidst dangers such as a field of battle never presented, and from which some of the bravest brutes that ever lived would have shrunk in dismay. These truly brave Valaisans deserve all honour !”
But the skill of M. Venetz was not limited in its application to emptying the lake : his abilities have been properly directed to the prevention of such another catastrophe for the liability to its recurrence was obvious. Not one twentieth part of the ice which formed the barrier, had been removed when the dike burst, and fresh masses were still falling from Mont Pleureur and Mont Mauvoisin, the mountains of which the bases formed the buttresses to the dike; in fact the dike was again accumulating so rapidly, that at the end of 1819 ibe barrier was almost as complete, as before its bursting from the pressure of the lake.
It became therefore an important object to prevent a repetition of the former catastrophe, by the adoption of such means as would prevent, or at least diminish, the increase of the barrier. Blasting by gunpowder was found impracticable, from the difficulty of firing the powder at considerable depths in the ice, and from the comparatively small masses removed by this means. After much consideration and many trials, a mode has been adopted and put in execution by M, Venetz, which promises the greatest success.
“ M. Venetz had remarked that the glacier could not support itself where the river was of a certain width, but fell into it and was dissolved; whereas, where the river was comparatively narrow, the ice and snow formed a vault over it, and consequently tended to the preservation of any portion falling from the glacier above. Perceiving also the effect of theriver iu dissolving the part it came in contact with, he formed and exe
cuted the design of bringing the streams of the neighbouring mountains by a canal to Mauvoisin, opposite the highest part of the glacier where it touched that mountain. From hence it was conducted bywooden troughs on to the glacier in a direction parallel to the valley. The water was divided into two streains : one falling nearly on the one edge of the Drance,
and the other on the other; and having been warmed by the sun in its course, soon cut very deep channels in the ice. When they reached the river the troughs were removed a few feet, andibus the stream produced the effect of a saw, which, dividing the ice, forced the portion between them to fall into the Drance.
“When the weather is fine, these streams, which are not more than four or five inches in diameter, act with extraordinary power, piercing a hole 200 feet deep and six feet in diameter in 24 hours. They are calculated to remove 100,000 cubical feet of ice from the barrier daily, and it is supposed that is the weather is fine the whole will be removed in three years.
“At the end of the season of 1822 the Drance remained covered only for a length of 480 feet; whereas, at the commencement of the operation, it was covered over a length of 1350 feet. M. Veneiz estimates the quantity of ice removed in 1822 as between eleven and twelve millions of cubical feet."--Bib. Univ. xxii. 58.
The châlets above Getroz can be reached in good time in one day from Martigny; and those who wish to cross the glaciers of Charmontane can sleep at the châlets, and, starting early the next morning, push on to the extremity of the valley, cross two glaciers, and attain the summit of the pass of the Col de la Fenêtre in time to reach Aosta on the following day.
These enormous glaciers have a greater extent, commanded at one glance, than perhaps any other in the Alps. With crampons on the feet, the traverse, it is stated, by one who has recently passed,' is neither dangerous nor difficult, but very fatiguing from their great extent. As they are seen to stream into their channel from the lofty peaks of the Combin and the Velan, they offer to the enterprising traveller one of ihe grandest views in the Alps. The elevation of the Col de la Fenêtre exceeds 9000 English feet, and the view from this crest extends over the southern mountains which bound the Val Pellina, to the peaks of the Iseran and the Cogne.
From the Col de la Fenêtre the descent is long and fatiguing to Balme, the first hamlet, and to Ollomont, where There are traces of an aqueduct built by the Romans for the supply of water to Augusta Prætoria. I'hence the road descends through the village of Valpellina, and still lower that