What renders a passage over this valley still more difficult and dangerous is, the rents in the ice, which are to be met with, whatever direction you follow. These rents are from two to six feet wide, and of an amazing depth; reaching from the surface of the valley, through a body of ice many hundred fathoms thick. On throwing down a stone, or any other solid substance, we could hear the hollow murmur of its descent for a very long time, sounding like far distant waves breaking upon rocks. Our guides, emboldened by habit, skipped over these rents without any sign of fear, though they informed us, that they had often seen fresh clefts formed, while they walked on the valley. They added, indeed, for our encouragement, that this was always preceded by a loud continued noise, which gave warning of what was to happen. It is evident, however, that this warning, though it should always precede the rent, could be of little use to those who had advanced to the middle of the valley; for they neither could know certainly in what direction to run, nor could they have time to get off: and in case the ice should yawn directly under their feet, they must inevitably perish.—But probably few accidents of that kind happen; and this has greater influence, than any reasoning upon the subject. It is supposed, that the snow and ice at the bottom melting by the warmth of the earth, leave great vacancies, in the form of vaults. These natural arches support for a long time an amazing weight of ice and snow;—for there is a vast distance from the bottom to the surface of this valley.—But the ice beneath continuing to dissolve, and the snow above to increase, the arches must at last give way, which occasions the noise and rents above mentioned. Water, also, which may have fallen from the surface into the clefts, or is lodged by any means in this great mass of snow, will, by its sudden expansion in the act of freezing, occasion new rents at the surface. We had heard a great deal of the havoc made by avalanches. These are formed of snow driven by the winds against the highest and most protuberant parts of rocks and mountains, where it hardens and adheres sometimes till a prodigious mass is accumulated. But when these supporters are able to sustain the increasing weight no longer, the avalanche falls at once, hurrying large portions of the loosened rock or mountain along with it;—and rolling from a vast height, with a thundering noise, to the valley, involves in certain destruction all the trees, houses, cattle, and men, which lie in its way[2]. The greater part of those who have made a journey to the Glaciers have seen one or more of these avalanches in the very act of falling, and have themselves always escaped by miracle.—Just as most people who have made a single voyage by sea, if it were only between Dover and Calais, have met with a storm, and very narrowly escaped shipwreck.