COS, or Stanko (Ital. Stanchio, Turk. Istan-keui, by corruption from Εἰς τὰν Κῶ), an island in that part of the Turkish archipelago which was anciently known as the Myrtoan Sea, not far from the south-western corner of Asia Minor, at the mouth of the Gulf of Halicarnassus, or Bay of Budrum. Its total length is about 25 m. and its circumference about 74. Its population is estimated at about 10,000, of whom nearly all are Greeks.

A considerable chain of mountains, known to the ancients as Oromedon, or Prion, extends along the southern coast with hardly a break except near the island of Nisyros; so that the greatest versant and most important streams turn towards the north. The whole island is little more than a mass of limestone, and consequently unites great aridity in the drier mountain regions with the richest fertility in the alluvial districts. As the attention of the islanders is mainly directed to the culture of their vineyards, which yield the famous sultana raisins, a considerable proportion of the arable land is left untouched, though wheat, barley and maize are sown in some quarters, and melons and sesamum seed appear among the exports. The Cos lettuce is well known. Fruit, especially grapes, is exported in large quantities to Egypt, mostly in local sailing boats. The wild olive is abundant enough, but neglected; and cotton, though it thrives well, is grown only in small quantities. As the principal harbour, in spite of dredging operations, is fit only for smaller vessels, the island is not of so much commercial importance as it would otherwise be; but since 1868 it has been regularly visited by steamers. The only town in the island is Cos, or Stanko, at the eastern extremity, remarkable for its fortress, founded by the knights of Rhodes, and for the gigantic plane-tree in the public square. The fortress preserves in its walls a number of interesting architectural fragments. The plane-tree has a circumference of about 30 ft., and its huge and heavy branches have to be supported by pillars; of its age there is no certain knowledge, but the popular tradition connects it with Hippocrates. The town is supplied by an aqueduct, about 4 m. in length, with water from a hot chalybeate spring, which is likewise named after the great physician of the island. The villages of Pyli and Kephalas are interesting, the former for the Greek tomb of a certain Charmylos, and the latter for a castle of the knights of St John and the numerous inscriptions that prove that it occupies the site of the chief town of the ancient deme of Isthmos. The most interesting site on the island is the precinct of Asclepius, which was excavated in 1900–1904 on the slope of Mount Prion, about 2 m. from the town of Cos. It consists of three terraces, the uppermost containing a temple, a cypress grove and porticoes; the middle, which is the earliest portion, two or three temples, an altar, and other buildings; and the lower a kind of sacred agora enclosed by porticoes. The precinct had been enlarged and reconstructed at various times. The earliest buildings on the middle terrace probably date from the 6th century B.C. The temple on the upper terrace, with the imposing flight of steps by which it is approached, seems to belong to the 2nd century B.C. when the whole precinct was enlarged and reconstructed. After a destructive earthquake, the whole appears to have been rebuilt by Xenophon, the physician and poisoner of the emperor Claudius. The final destruction was brought about by the earthquake of A.D. 554. Among other things the precinct contains a fountain of water with medicinal properties. It is doubtful whether this water is brought from Burinna, the famous fountain of Hippocrates in the mountain above.

History.—Cos was a Dorian colony with a large contingent of settlers from Epidaurus who took with them their Asclepius cult and made their new home famous for its sanatoria. The other chief sources of the island’s wealth lay in its wines, and in later days, in its silk manufacture. Its early history is obscure. During the Persian wars it was ruled by tyrants, but as a rule it seems to have been under an oligarchic government. In the 5th century it joined the Delian League, and after the revolt of Rhodes served as the chief Athenian station in the south-eastern Aegean (411–407). In 366 a democracy was instituted. After helping, in the Social War (357–355), to weaken Athenian power it fell for a few years to the Carian prince Maussollus. In the Hellenistic age Cos attained the zenith of its prosperity. Its alliance was valued by the kings of Egypt, who used it as an outpost for their navy to watch the Aegean. As a seat ef learning it rose to be a kind of provincial branch of the museum of Alexandria, and became a favourite resort for the education of the princes of the Ptolemaic dynasty; among its most famous sons were the physician Hippocrates, the painter Apelles, the poets Philetas and, perhaps, Theocritus (q.v.). Following the lead of its great neighbour, Rhodes, Cos generally displayed a friendly attitude towards the Romans; in A.D. 53 it was made a free city. In A.D. 1315 it was occupied by the Knights of St John; in 1523 it passed under Ottoman sway. Except for occasional incursions by corsairs and some severe earthquakes the island has rarely had its peace disturbed.

Authorities.—L. Ross, Reisen nach Kos, &c. (Halle, 1852), pp. 11–29, and Reisen auf den griechischen Inseln (Stuttgart, 1840–1845), ii. 86 ff.; O. Rayet, Mémoire sur l’île de Cos (Paris, 1876); M. Dubois, De Co Insula (Paris and Nancy, 1884); W. Paton and E. Hicks, The Inscriptions of Cos (Oxford, 1891); B. V. Head, Historia Numorum (Oxford, 1887), pp. 535–537; Archäol. Anzeiger, 1905, i.; for coins see also Numismatics: Greek, § “Calymna and Cos.”  (E. Gr.; M. O. B. C)