TIERRA DEL FUEGO, an archipelago lying between 52° 27' and 55° 59' S. lat. and
43' and 74° 44' W. long. at the southern extremity of South America, from which it is separated by Magellan strait. At the First Narrows and at other points the strait is scarcely a mile wide. In shape the main island is a tri angle with its base in the Beagle channel. The total area is about 28,000 sq.m. of which 19,500 sq.m. belong to Chile and 8,5oo to Argentina. Argentina holds that part of the main island which lies east of the meridian of Cape Espiritu Santo (68° 36' 38" W.) and Chile holds all the western part of the main island and other numerous islands to the west and to the south of Beagle channel. The Argentine side is known as the Gobernacion of Tierra del Fuego (including Staten island) and the Chilean forms part of the Territory of Magellanes. Although in the '8os of the past century extensive deposits of alluvial gold were discovered, their exploita tion was not generally successful and farms took the place of mines. The Argentina census of 1914 reported 64 haciendas cover ing 4,83o sq.m. with about 800,000 sheep, 7,00o cattle and 5,000 horses on the Argentina side. The sheep industry is particularly profitable and growing rapidly.
The greater part of the main island is formed by the continuation of the Tertiary beds of the Patagonian table-land cut by the transversal depression of Magellan strait and by the lowland extending from Useless bay in the west to San Sebastian bay on the east and analogous to the transverse valleys of the Patagonian table-land. North of the lowland is an undulat ing table-land with an average height of 400 ft., intersected by numerous arroyos with little water and with good sheep pasture. In the west and south-west the general character of the main island changes ; the ends of the Tertiary beds are raised—small hills and Mesozoic rocks appear, forming broken ridges east of the main range of the Andes. In this region appears the Antarctic forest.
Lake Solier and Lake Fagnans receive the water from these moun tains and hills. To the south of the lake rises the south-eastern prolongation of the Andes with ridges at a uniform height of 3,500 ft. in which predominate crystalline schists. Some peaks of Tertiary granite break the uniformity, such as Mt. Sarmiento (7,54o ft.), Mt. Darwin (about 7,50o ft.) and Mt. Ulewaia (4,5oo ft.), called Olivaia on some maps.
The section of the archipelago south of Beagle channel in cludes the islands of Hoste, Navarin, Gordon, Londonderry, Stew art Wollaston and numerous islets, disposed in triangular form with the base on Beagle channel and the apex at Cape Horn. Im portant explorations in this region were conducted by the French Mission de Cap Horn (1882-83). The most recent explorations on the western part of the main island of Tierra del Fuego immedi ately south of Beagle channel (in the Fiords de Agostini, Admiral Martinez and others) were carried out by Alberto M. de Agostini in 1913-14. The western group of islands includes Clarence island (formerly believed to be a single island but now known to be divided by a channel into two sections kncwn as Santa Ives and Desolation islands) and numerous small islands and rocks.
At Ushuaia ten years' meteorological observations have shown a mean annual temperature of 42.8° F, with a winter mean of
a summer mean of 50.2°, and an average yearly precipitation of 24.8 inches. Of all winds, 8o% are westerly and a great difference in precipitation between the windward and lee ward sides of the islands has been noted not only in the western part but also on Staten and Observatory islands. Precipitation on all windward slopes is almost continuous, producing dense forests on the lower slopes, where it falls as rain, and snow and ice-fields on the upper slopes.
To the three geographical divisions correspond three well-marked ethnical groups—the Onas on the main island south of the Grande river, the Yagans (Yahgans) on the southern islands and the Alakalups on the western. The origin of the Onas, like that of the other groups, is obscure. Undoubtedly among them are many that resemble some Patagonian type ; but they seem to be not the same as the Tehuelche type and may pertain to one of the earlier Patagonian races. Their language is closely allied to that called Old Tehuelche ; it is a hard guttural, slow-spoken speech, not at all resembling the soft, rapidly-spoken language of the Yahgans, which has many points of similarity with that of the Alakalups. The isolation of the Onas is peculiarly marked as they are insular people who do not use boats. The Yahgans live under conditions of extraordinary rigour. In order to obtain food, they venture naked with small canoes into the tremendous seas.
Their life is a constant battle with starvation and a severe cli mate and their number is being rapidly depleted. They have no higher social unit than the family. The missionaries, who have reduced their language to writing, assert that it contains no less than 30,00o words, although the numerals stop at five, but it appears that a large number of words included in this total are compounds. Comparatively little is known of the Alakalups.
Tierra del Fuego was discov ered by Fernando de Magellan in 1520 when he sailed through the strait named after him and called this region "Land of Fire." In 1578 Sir Francis Drake first sighted the point which in 1616 was named Cape Hoorn (Anglicized Horn) by the Dutch navigators Jacob Lemaire and William Cornelis Schoote (1615-17). In 1619 the brothers Garcia and Gonzalo de Nodal first circumnavigated the archipelago. No systematic exploration was attempted until the British Admiralty undertook a thorough survey of the whole group by Philip Parker King (1762-1828) and Robert Fitzroy (1831-36). The latter expedition (Voyage of the "Beagle") was accompanied by Charles Darwin, then a young man. To these admirable surveys is due most of the present geographical termi nology of the archipelago, and although supplemented by later surveys in many parts by the Chilean navy they still form the basis and, to a large extent furnish the detail, for most hydro graphic charts of the region.