an ancient navigator, was a native of Marseilles, and is supposed to have lived some time about the age of Alexander the Great, 330 B.C. We have no information respecting the private circumstances of his life; but we know that he explored the northern seas of Europe, though the ancient geographers appear to have placed little dependence on the statements which he made. Both Polybius and Strabo treat him with great severity, and ridicule his accounts as absurd and incredible. It would appear that he sailed through the English Channel, and, after a voyage of six days to the north, reached an island which he calls Thule, where he says that the sun never descends below the horizon for a certain period at the summer solstice. This statement would apply to Iceland, but then it seems unlikely that he could reach that island within six days. He next sailed to the north-east, and entering the Baltic, reached a river which he calls Tanaïs, and is thought to be the Vistula. Here he found a people who made use of amber instead of wood; and as that substance is still found in large quantities in Prussia, there is little doubt that he must have visited this part of Europe. He gave an account of his voyages in two works which he published. The one was entitled a Description of the Ocean, and contained his voyage from Gades to Thule; the other work was entitled Periplos. It is said that Pytheas was the first who suspected that the tides were influenced by the moon. (See Éclaircissements sur la Vie et sur les Voyages de Pythéas, by Bougainville, in the Recueil de l'Académie des Inscriptions, xix. 46.)