The Arveiron is a powerful torrent that issues from the lower end of the Glacier des Bois through a great arch of ice, which the local people call the Arveiron’s “embouchure” or mouth, although this is actually its source, or at least the first place where it comes out into the open air. One can get there, as I have said, directly by descending from Montenvers; but this is a path so steep and strenuous that I can hardly recommend it. From the Prieuré, by contrast, there is a charming walk of an hour or one could even take a carriage, all on the flat, across beautiful meadows and through a splendid forest.
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| Source of the Arveiron: print made by Sigismond Himely, 1820s From the British Museum collection |
The Arveiron’s source is worthy of any traveller’s attention. It is a deep cavern, with the entrance formed by a vault of ice more than a hundred feet high, and of proportionate width. Carved as if by the hand of nature, the cavern opens amid an enormous mass of ice, which shines opaquely and white as snow here, or a translucent aquamarine there, just as the light may play on it. From the bottom of this cavern, a river surges out, foaming white and, ever and again, tumbling in its waves large floes of ice.
Raising your eyes above this vault, you see an immense glacier, crowned by pyramids of ice, amid which the obelisk of the Dru thrusts upwards, its summit lost in the clouds. Finally, this whole picture is framed by the beautiful woods of the Montenvers and the Aiguille du Bochard, these forests running upwards alongside the glacier as far as its highest reaches, which merge into the sky.
The place where one enjoys this spectacle is extremely wild; since the ice has greatly diminished, there remain only piles of sand and blocks deposited by the glacier; one sees no verdure. But seven or eight years ago, when the glacier came down much lower, the ice cavern was situated next to a larch wood floored with a beautiful white sand sprinkled with clumps of the beautiful red blooms of the epilobium, the starry flowers of Sempervivum arachnoideum, and those of the Saxifraga autumnalis.
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| Source of the Arveyron: watercolour by Samuel Grundman, 1826 By courtesy of Chamonix City Office |
I have sometimes been inquisitive enough to enter this cave, and indeed one can go quite far inside when it is wide enough and the Arveiron does not fill it up; but this is always a temerity, as the vault often drops large fragments. When we went to visit it in 1778, we noticed in the arch which formed the entrance to the vault a large, almost horizontal fissure, cut at its ends by vertical cracks. It was easy enough to see how this whole piece would soon come adrift and, indeed, a report like a thunderclap was heard that very night. This piece, forming the vault’s keystone, had collapsed, dragging down the whole outer part of the arch. The ice mass had then blocked the course of the Arveiron for some moments. Pooling up in the bottom of the cavern, the waters then burst abruptly through the dam, violently sweeping away all these great blocks of ice, smashing them to pieces against the rocks that stud the torrent’s bed and carrying the fragments far and wide. The next day, with a sort of horror, we saw how large slabs of this ice covered the place where we had stood the day before.
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| Interior of the ice cave at the source of the Arveiron By Samuel Grundmann and J-P Lamy Alpine Museum of Chamonix-Mont Blanc |
So this is how the vault collapses and how it renews itself. In winter, it hardly exists; the shrunken Arveiron creeps out from under the ice, which slopes down to ground level, and it is only when the growing warmth of spring swells the waters of this torrent and melts away some of the ice that the rivers starts gnawing at the icy walls that resist its passage, and then those in the middle, no longer supported, collapse into the stream, which carries them along, successively breaking away more and more fragments until the upper part of the ice takes the form of a vault whose blocks hold each other up. This vault changes from day to day; sometimes it collapses entirely, but soon a new one is formed.
It may be asked why this glacier is the only one that ends in such a large and beautiful ice arch. This is because it is the only one, at least to my knowledge, which has ice of such great depth and consistency at its lower end, and which terminates on horizontal ground, and from which emerges such a considerable torrent, as all these conditions must be fulfilled in order to produce a beautiful arch. If the glacier ends on a steep slope, as they very often do, the slightest movement of the glacier causes the ice blocks to tumble down, giving an arch no time to form. Then, if only a little water issues from the glacier, the arch is necessarily narrow and low in proportion, because it is the breadth of the torrent which determines that of the arch, and thus its height. And if, finally, the ice is thin or fragile, no arch can be either sizeable or stable.
Moreover, this vault of ice is not always so impressive or vast, nor does it remain always in the same place. This is because the glacier sometimes advances into the valley, and at other times retreats. The granite blocks it has deposited show that it once descended much lower on this slope than it does today.
References
Translated from Horace-Bénédict de Saussure, Voyages dans les Alpes, édité et présenté par Julie Boch, Genève, Georg éditeur, 2002
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