repetition of similar features. It is almost impossible to go twice over the same road on the glacier, and nothing is so easy as to get into a maze of crevasses, some of which are impassable. Our guides were several times perplexed; but were relieved by discovering some piles of stones which had been set up by the guides, who, the day before, had conducted some travellers to the Jardin. A sort of general route is marked out by the guides, and adhered to as much as possible; but the changeful nature of the glacier and its edging moraines renders it impossible to fix any thing like permanent land marks. And yet, amidst all this change, there is a certain steadfastness of form which is wonderful. Year after year, an experienced guide will appear to go in nearly the same path, avoiding the same crevasses, and pointing out the same moulins and other objects of interest, and yet, by the progressive movement of the glacier, the ice is wholly changed. The bed of the glacier and the rocks at the side remaining nearly always the same, the ice is twisted into the same forms, and hence appears to be at rest. Such then is the glacier as we witnessed it in the Mer de Glace, which combines all, or nearly all, DIMENSIONS OF THE MER-DE-GLACE. 115 the chief features of glacier scenery. The length of the whole Mer de Glace is said to be eighteen leagues; but a league is generally understood to mean an hour's walk among the mountains. According to Mr. Forbes's survey, the shortest line from the foot of the glacier to the highest ridge of the Alps is about seven miles, and the breadth of the glacier seldom exceeds two-thirds of a mile, but is generally much less. This, however, gives no idea of its apparent extent,—the toil of traversing it, and the endless turns among its crevasses, make an enormous addition to the distance. On descending into the valley of Chamouny, blocks of moraine lie scattered here and there, forming a wilderness of stones of all shapes and sizes, showing how far the ice had in former years extended. And long after quitting the region of the glacier, huge stones, precisely similar to those seen on and about the ice, are to be met with indeed, they are scattered over many parts of Europe, and are hence called erratic or wandering blocks; they are also called boulders. A great belt of these stones extends for miles, at a height of about 800 feet above the level of the lake of Neufchatel. One of these blocks, situated about two miles to the west of the town of Neufchatel, is called the Pierre à Bot, or the Toad-stone, from its rude resemblance to the form of a crouching toad. This stone is fifty feet long, twenty wide, and forty high, and contains about 40,000 cubie feet of solid material. It was suggested many years ago by Professor Playfair, that these erratic blocks were deposited by ancient glaciers, which have since retreated within narrower limits. Speaking of the Toad-stone, he says, "A current of water, however powerful, could never have carried it up an acclivity, but would have deposited it in the first valley it came to, and would, in a much less distance, have rounded its angles, and given to it the shape so characteristic of stones subject to the action of water. A glacier, which fills up valleys in its course, and which conveys rocks on its surface free from attrition, is the only agent we now see capable of transporting them to such a distance without destroying that sharpness of the angles so distinctive of these masses." Another proof of the former existence of glaciers is to be found in polished rocks, which are seen many miles away from the site of any existing glacier. It has been already noticed, (p. 92) that the ice, |