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Show 286 TIERRA DEL FUEGO. June, 1834. found much further northward: and considering the immense size of the one just described, it is extremely improbable that it should be the last. On the island of Chiloe, which fronts the Cordillera as the Jura does the Alps,' many angular fragments of granite, of an enormous size, which appear to have crossed the inland arm of sea, lie scattered at different heights over the country. Although situated between the parallels of 41° and 43°, I know of no sound objection to the supposition that these might formerly have been floated across, on icebergs produced by the fall of glaciers. We are not bound to suppose that the latitude 46° 40' has always been the northern limit of such phenomena, even if it should be so at present. We have endeavoured to show that the snow-line in the parallel of Chiloe has an elevation of about 6000 feet; and since on Mont Blanc the glaciers descend 5160 feet beneath the line of perpetual snow, we might at present expect to find them in front of Chiloe at a very small altitude above the level of the sea. With respect to the position of the glaciers, they seem to occur only within the deep sounds which penetrate the central Cordillera. This may be attributed chiefly to the subordinate elevation of the outer lines. When we consider the vast dimensions and number of these glaciers, the effect produced on the land must be very great. Every one has heard of the mass of rubbish propelled by the glaciers of Switzerland, as they slowly creep on wards. In the same manner in Tierra del Fuego, on a still night the crackinO' and • b groamngofthe great movingmassmay be distinctly heard. The same force, which is known to uproot whole forests of lofty trees, must, when grating over the surface, tear from the flanks of the mountain many huge fragments of rock. Beneath each ~lacier, also, a roaring torrent drains the upper part of the Ice. To these effects, which are common to all cases, there must be added, in this country, the wear and tear of the waves produced by each successive fall. Nor can this agency be inconsiderable, when we remember that it goes on night and day, century after century. We must look June, 1834. GLACIERS. 287 at every portion of the mountain as having, during the gradual rising of the land, been successively exposed to the action of these combined forces. It is, perhaps, useless to speculate on the effects of earthquakes without some positive data. But as we find in the immediate neighbourhood of that great glacier, which stands in the latitude of the Alps, Byron* mentioning with surprise the quantities of sea-shells lying on all the hill-tops (a fact which may be taken as a proof of recent continental elevations); and Bulkeley,t in his narrative, saying, "This day we felt four great earthquakes, three of which were very terrible;" we may feel well assured, that the same power, which in Chile causes such vast masses of rock and soil to fall from the sea-cliffs, has oftentimes precipitated fragments far more immense, of a mass traversed by great fissures, already in motion, and resting on an inclined plane. I cannot imagine any scene of more terrific violence, than the waves produced by such a fall : we know that they are very bad from the mere oscillation, consequent on the movements of the ground; but in this case I can readily believe that the water would be fairly beaten back out of the deepest inlet, and then returning with an overwhelming force, would whirl about rocks of vast size like so much chaff. In after ages, with a climate modified by the process of such physical changes as are now going on throughout the greater part of this continent, the effects which had been produced by these glaciers would appear inexplicable, to a person who doubted the possibility of their occurrence in such latitudes. He would see in the most retired and protected valleys (the present channels) beaches composed of great rounded boulders, such as those heaped up on the shore of the most turbulent ocean. Then perhaps he would speculate, either that the outer chain of mountains had been elevated • Byron's Narrative of the Shipwreck of the Wager. t Bulkeley's and Cummin's Faithful Narrative oft.he loss of the Wagct·. The earthquake happened August 2!), 1741. |