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Show 280 TIERRA DEL FUEGO. June, 1834. mass in its downward course. They have been aptly compared to gigantic icicles. The lower limit of glaciers, must depend on that of the parent snow, greatly affected by the form of the land : in Tierra del Fuego the snow-line descends ve.ry low, and the mountain sides are abrupt; therefore we might expect to find glaciers extending far down their flanks.* Nevertheless, when on first beholding, in the middle of summer, many of the creeks on the northern side of the Beagle channel terminated by bold precipices of ice overhanging the salt water, I felt greatly astonished. For th~ mountains from which they descended, were far from bemg very lofty. Captain FitzRoy from angular measurements considers the general range to have an elevation rather under 4000 feet, with one point called Chain Mountain rising to 4300. Further inland, there is indeed a more lo~ty mountain of 7000 feet, but it is not directly connected With the glaciers to which I now allude. This range, which exceeds by so little the height of some mountains in Britain which yet sends down in the middle of summer its froze~ streams to the sea-coast, is situated in the latitude of the Cumberland hills. I was much interested by observing the great difference b~tween the matter brought down by torrents and by glaCiers. In the former case a spit of gravel is formed but in th~ latter a pile of boulders. On one occasion, th~ boats bemg .hauled on shore, within the distance of half a mile from a glacier, we were admiring the perpendicular cliff of blue ice and wishing that some more fragments would fall off. lik~ those we saw floating on the water, at a distance of 'more than a mile from their source. At last, down came a mass . ~ In the Alps, Saussure gives 8793 feet as the mean of the lower hm1t of the snow-line. At Mont Blanc the glacier of Montanvert is said (Encycl?. Metrop.ol.). to descend 12,000 feet below the summit of the mountam, and tl11s will make its base 5160 feet lower than the line of snow. In, Norway (See Von Buch) where a glacier first comes down to the water's edge (lat. 67°), it is 3800 below the same line : in Tierra del Fuego the difference must be very nearly the same as in the last case, June, 1834. GLACIERS. 281 with a roaring noise, and immediately we saw the smooth outline of a wave travelling towards us. The men ran down as quickly as they could to the boats ; for the chance of their beina dashed to pieces was evident. One of the seamen just ':l • caught hold of the bows, as the curling breaker reached It: he was knocked over and over but not hurt; and the boats, though thrice lifted on high and let fall again, received no damage. This was most fortunate for us, for we were a hundred miles distant from the ship, and we should have been left without provisions or fire-arms. I had previously observed that some large fragments of rock on the beach had been lately displaced : but until seeing this wave I did not understand the cause. The structure of the creek in which this happened was very curious. One side was formed by a spur of mica slate (of which rock the surrounding mountains were composed) ; the head by a cliff of ice about forty feet high; and the other side by a promontory which was built up of huge rounded fragments of granite and mica slate, and was more than fifty feet in height. 'ro account for the present position of these blocks, where they must have long remained, for old trees were growing on the upper parts ; we must suppose, either that the glacier formerly advanced half a mile further outward, or that the land stood at a rather different level. Whether we are able fully to account, or I)ot, for the height and size of this promontory of boulders, certainly it must have been ~he w~rk of the glacier. One semi-rounded fragment of gr~mte ~ymg just above high-water mark, was of enormous dime~siOns. It projected six feet above the sand, and was buned to an unknown depth : its shape was oval with a circumference of thirty yards, so that the longer axis probably measured about ten or eleven. This fragment must have come from the higher parts of the range ; for the base of the mountain was entirely composed of mica slate. 11he waves caused by the fall of the ice must be a most powerful agent in rounding and heaping tog~th~r thes~ huge fragments, and likewise in wearing away proJectmg pomts of |