In less than an hour we had got over a greater distance than we had the whole of the previous day.  We had now reached the entrance to the pass. On either side rose pyramidical peaks, covered with perpetual snow, three thousand feet above the valley.  Shortly afterwards we came to the foot of a magnificent glacier, which must have been scarcely less than a mile in length and several hundred feet in height.  As we had made a good day's journey, and evening was approaching, Uncle Donald was looking out for a place at which to camp.  We had just fixed on a spot on the bank of the river at the edge of a thick belt of trees, which here intervened between it and the cliffs, when a roar as of distant thunder reached our ears.