Ptolemy II, surnamed Philadelphus, king of Egypt, youngest son of the preceding by Berenice, born in the island of Cos in 309 B. C, died in Alexandria in 247. He was carefully educated, and was thoroughly imbued with his father's policy. He cleared Upper Egypt of robbers, penetrated Ethiopia, establishing traffic with the tribes, and opened southern Africa to the Alexandrian merchants. To command the Red sea, he founded ArsinoŽ (near Suez), and connected it with Alexandria by restoring and completing the canal begun by Necho. He constructed the ports of Myos-Hormos and Berenice, and connected the latter with Coptos on the Nile by a road 258 m. long across the desert. The museum founded by his father was improved by the addition of botanical and zoological gardens, works of art were collected from Greece, and large additions were made to the library. (See Alexandrian Library.) He spent vast sums on public works, built the celebrated lighthouse on the island of Pharos, and erected a magnificent royal mausoleum, to which he removed the remains of Alexander the Great from Memphis. The most distinguished poets, philosophers, mathematicians, and astronomers resided at his capital.

For the use of the Alexandrian Jews, the Septua-gint version of the Hebrew Scriptures is said to have been made by his command. His reign was disturbed by the revolt of his half brother Magas, viceroy of Cyrene, who succeeded in maintaining his independence; and by a contest with Syria for the possession of Phoenicia and Coele-Syria, which was kept up at intervals till near the close of his life, when these provinces at last remained in his possession. He took part several times in the affairs of Greece, maintaining an unfriendly attitude toward Macedon, and established relations of amity with the rising republic of Rome. He founded a gymnasium at Athens, and planted numerous colonies in various parts of his foreign dominions, which comprised Phoenicia, Coele-Syria, Palestine, Cyprus, the Cyclades, and portions of southern Asia Minor, Ethiopia, Arabia, and Libya. The effeminacy of his court increasing with the wealth of the country, he came at length to lead the indolent life of a refined voluptuary. Repudiating his first wife, ArsinoŽ, daughter of Lysimachus, he married his own sister ArsinoŽ, widow of Lysimachus, which the Egyptian law allowed, but she brought him no children.

Another stain on his memory is the execution of two of his brothers, for which his surname, which he himself had assumed to signalize his attachment to his sister, became a subject of derision.