National Geographic : 1900 Feb
50 GEOGRAPHIC FEA TURES OF SOUTHERN PATAGONIA Since Dr Moreno's paper is doubtless easily accessible, I shall not attempt a detailed description of this interesting region, but shall briefly discuss the factors which have contributed to produce the existing unusual drainage conditions. I am the more easily impelled to this course, since some of the theories advanced by Dr Moreno in explanation of certain features described by him appear to me un tenable. At any rate, they are not supported by most of the observa tions made by myself during the past three years. A study of the southern Andes at any point reveals the fact that they are composed of three distinct, parallel ranges, separated by two deep, narrow, longitudinal valleys. The middle of the three ranges is everywhere much higher than the two lateral ranges and may be reckoned as the principal range of the Andes. The western lateral range is at present partially submerged beneath the Pacific, but is still distinctly seen in the chain of islands extending all along the western coast. The western of the two longitudinal valleys is at present throughout the greater extent of Patagonia entirely sub merged beneath the sea and is now represented by the narrow sys tem of rather deep channels that separates the islands from the main land and offers an almost continuously navigable inland waterway extending from the southernmost point of the Brunswick Peninsula to the 42d parallel of south latitude, or throughout more than twelve degrees, a distance of over 700 miles. The eastern lateral range of the Andes is seen in the foothills that rise somewhat abruptly from the eastern plains to a height in places of some 6,000 or 7,000 feet. They are composed almost entirely of Secondary and Tertiary sedimentary rocks, with occasional layers of intrusive basalts, the whole thrown up in a somewhat complicated system of folds of usually monoclines or anticlines terminating toward the west in a lofty escarpment, the crest of which overlooks the deep, narrow, and irregular, eastern longitudinal valley that sep arates the eastern lateral range from the central main range of the Andes. In this eastern longitudinal valley there is located a series of the most beautiful mountain lakes, extending northward in a somewhat broken chain from Lake Argentina, at the head of the Santa Cruz River, to the northern limits of Patagonia. At some dis tance to the south of Lake Argentina the bottom of the valley has not been sufficiently elevated and it is here occupied, not by fresh water lakes, but by numerous narrow arms of the Pacific, as seen in Last Hope Inlet, Obstruction Sound, Skyring and Otway waters, and Useless Bay, opposite Sandy Point, in the Strait of Magellan.