Juan Fernandez, an island in the South Pacific ocean, in lat. 33° 38' S., lon. 78° 46' W., about 420 m. W. of Valparaiso, belonging to Chili. It is of irregular form, about 12 m. in length from E. to W., but not more than 4 m. across in the widest part. A small detached portion at the S. W. end is called Santa Clara island. About 92 m. W. lies a small island called Mas-a-Fuera (further off shore), Juan Fernandez being distinguished as Mas-a-Tierra (nearer the mainland). Mas-a-Fuera is covered with trees and well provided with fresh water; but being destitute of anchorage or landing place, it is seldom visited, and very little known. Juan Fernandez is, like most of the isolated oceanic islands, of volcanic origin, though the original shape and position of the crater are difficult to trace. The principal material in its formation is a stratified tufa, interspersed with blocks of harder volcanic rocks, such as vesicular lava and greenstone. The N. E. part is high, rising to 3,000 ft. in the mountain called El Yunque (the anvil). The headlands form abrupt cliffs toward the sea, and are separated by narrow valleys, clothed in rich vegetation, and watered by small streams of excellent water.

The S. W. prolongation of the island is less elevated, forming a plateau covered with grass, destitute of trees, and bordered by cliffs. A few other parts of the S. shore present the same appearance. The island is very picturesque, particularly when approached from the north. The mountains, rising rapidly from the sea, have when seen from that side an aspect of grandeur which they lose when seen from other directions. Notwithstanding their steepness, which renders most of the summits inaccessible, they are wooded to the top. The only anchorage in use is Cumberland bay in the N. E. part; it is well sheltered from the southerly winds, which are the prevailing ones in summer. Two valleys open into this bay, and at their confluence is situated the settlement, consisting of a few Chilian huts, surmounted by the remains of a fort. - The first settler on the island was a Spaniard, after whom it is named, who resided here with his family, but afterward went to live on the newly conquered mainland of Chili. Subsequently the island was for a long time a debatable ground between the Spaniards and the buccaneers, the latter finding it a convenient place to refit within easy distance of the Spanish settlements.

To that period may be attributed the numerous small batteries of which the remains can be seen in Cumberland bay, and, according to the residents, in all the small bays in which a landing might have been attempted. At one time it was made the seat of a Chilian penal settlement. To the labor of the convicts are due the series of large caves, dug in the side of the hill above the anchorage, now being rapidly closed up by the crumbling of the hillside. A foot path over the Yunque range, through a pass 1,800 ft. high, was also constructed by them. In 1872 only a dozen Chilians resided on the island, cultivating a few vegetables, and raising poultry in limited quantities; but they were supplied with most of the necessaries of life from Valparaiso. - It is doubtful whether there were any native land mammals on the island at the time of its discovery. Anson indeed speaks of having seen the burrows of an animal called pardela by older writers, which he thought to be then extinct. Goats were early introduced, perhaps by Juan Fernandez himself. They multiplied enormously, and formed the chief supply of the buccaneers who used the island as a rendezvous.

The viceroy of Peru caused a large number of dogs to be landed, in the hope that they would destroy the goats and thus deprive the buccaneers of this resource; but the steepness of the summits and of the cliffs preserved many of those animals. When Anson visited the island (1741) the dogs were still numerous, but subsisted chiefly on young seals. At present they have been nearly exterminated by the settlers, and the goats have increased again, though mostly confined to the southern slope of the island. Horses and asses roam over the island in a half wild condition; horned cattle and a few sheep are kept by the settlers, but apparently in numbers much below the resources of the pasture offered. The shores were formerly frequented by large numbers of seals, sea lions, and sea elephants. The last are extinct, as on the neighboring coast of South America, and the first have become much less numerous. A thrush-like bird and one or two of smaller size are found in the woods. A fine humming bird is abundant at a considerable elevation; and a few hawks may occasionally be seen. Most of these birds are peculiar to this island. Pigeons, resembling the European rock pigeon, frequent the cliffs on Cumberland bay, and may have been introduced.

Few sea birds are seen except at the breeding season on some of the islets on the S. side. No reptiles have been found here. Fish are abundant, and are dried for the Chilian market, to which are also sent the dried tails of a large crawfish. - The most striking parts of the vegetation are a myrtle-like tree, the aromatic wintersbark, tree ferns, and a large variety of other ferns. A remarkable palm, peculiar to the island, but very limited in numbers, grows only on a few inaccessible summits. Apples, plums, apricots, and peaches were planted by Anson, and have become plentiful. Fig trees grow luxuriantly near the settlement, where also turnips and radishes run wild in abundance. A species of Gunnera, with enormous leaves, forms a beautiful ornament, overhanging the small streams at the bottom of the valleys. Strawberries abound. The pasture lands are covered with a species of oat, besides other grasses. - A romantic interest attaches to this island through the story of Alexander Selkirk, supposed (though probably without reason) to have given to Defoe the idea of "Robinson Crusoe." (See Defoe.) Selkirk, a Scotch sailing master on board the ship Cinque Ports of Dampier's squadron, was left on this island at his own request (1704), on account of differences with his captain.

He remained in solitude four years and four months, and was finally taken off in February, 1709, by Capt. Woodes Rogers. After having exhausted his ammunition, he subsisted by running down and catching goats. Tradition points to a cave in the bay next west to Cumberland bay as his habitation. The summit of the pass over the Yunque range is called his lookout, and a tablet reciting the principal points of his history has lately been placed there by the officers of the British ship Topaz. Previously to Selkirk, a Mosquito Indian had been accidentally left behind, and taken away again, after the lapse of three years, by Dampier.