up, until, I suppose, we were not more than a thousand feet below the point marked 3912 metres; then a bridge was discovered, and we dropped down on hands and knees to cross it.
A bergschrund, it was said on p. 238, is a schrund, and something more than a schrund. A schrund is simply a big crevasse. A bergschrund is frequently, but not always, a big crevasse. The term is applied to the last of the crevasses that one finds, in ascending, before quitting the glacier, and taking to the rocks which bound it. It is the mountains' schrund. Sometimes it is very large, but early in the season (that is to say in the month of June, or before) bergschrunds are usually snowed up, or well bridged over, and do not give much trouble. Later in the year, say in August, they are frequently very great hindrances, and occasionally are completely impassable.
They are lines of rupture consequent upon unequal motion. The glaciers below move quicker than the snow or ice which clings immediately to the mountains; hence these fissures result. The slower motion of that which is above can only be attributed to its having to sustain greater friction; for the rule is that the upper portion is set at a steeper angle than the lower. As that is the case, we should expect that the upper portion would move quicker than the lower, and it would do so, doubtless, but for the retardation of the rocks over which, and through which, it passes.[1]
We crossed the bergschrund of the Dent Blanche, I suppose, at a height of about 12,000 feet above the level of the sea. Our work may be said to have commenced at that point. The face, although not steep in its general inclination, was so cut up by little ridges and cliffs, and so seamed with incipient couloirs, that it had all the difficulty of a much more precipitous slope. The difficulties were never great, but they were numerous, and made a very respectable total when put together. We passed the
