The spread of colonization toward the south during the last generation has extended Argentine territory beyond the limits of these classic scenes. The Patagonian Andes differ profoundly from the Northern Andes; and the change is not more sudden than that of the climate, to which it is due. Going toward the south, one passes, almost without a break, from the Atlas Mountains to Scandinavia. The moisture increases in proportion as the mean temperature falls. The mountains are covered with snow, and the glaciers lengthen. In one part of Patagonia they still form a continuous cap, an "inland sea," concealing the rock over the entire central zone of the Cordillera; though they are only the shrunken remainder of a glacial cap which was once far more extensive. Here ice was the chief sculptor of the scenery. It has made elevated tablelands, broadened the deep valleys which cut the flank of the mountain, polished their sides, and deposited at the point where they open out the amphitheatres of the moraines, behind which the waters have accumulated and formed lakes; and these lakes stretch back like fiords to the heart of the Cordillera, and are the pride of Patagonia. The waters of these moisture-laden mountains have, to the east, carved out the Patagonian tableland. It is crossed by broad and boldly cut valleys, several of which, abandoned by the rivers which scoured them, are now dead valleys. The rubbish from the wearing down of the mountains and the glacial moraine has been spread over the whole face of the tableland in the form of beds of gravel. But the rivers that rise in the Andes cross a country of increasing aridity as they descend eastward. There is no tributary to add to their volume. There is none of that softening of lines, of that idle flow of a meandering stream which characterizes the final stage of a river in a moist district. Their inclination remains steep, and their waters continue to plough up coarse sediment; and everywhere, up to the fringes of the valleys, the fluting of the sandstone and steepness of the cliffs bear witness, like the edges of the _hamadas_ of the Sahara, to some other form of erosion than that effected by running water--the influence on the country of the westerly winds. On the tableland the wind polishes the rounded pebbles, makes facets on them, and gives them the colouring of the desert.