an ancient navigator, was a native of Massilia, 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. Modern writers are inclined to set more value upon the narrative of Pytheas. It would appear that he sailed through the English Channel, and, after leaving Britain, a voyage of six days to the north brought him to 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 N.E., and entering the Baltic, reached a river which he calls Tanais, and is thought by Ukert to be the Elbe. 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 a Description of the Ocean, and contained his voyage from Gauls to Thule; the other work was entitled Periplus. He appears to have been the first to determine the latitude of a place from the sun's shadow. 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 Pythias, by Bougainville, in the Recueil de l'Académie des Inscriptions, xix. 46; also the discussions of D'Anville, of Ukert, of Arvedson, of Fuhr, and of Straszewick.)