CATHAY, the name by which China became known to mediaeval Europe. It is derived from Khitai, the name of the kingdom of Khitan Tartars (loth and i 1 th centuries A.D.) which, based on Manchuria (the north-east gateway into China), in cluded at times part of north China as well, and which towards its close had its capital at Yenking (Kublai Khan's Cambaluc, q.v., and the modern Peking). The Central Asian Tartars, in touch only with its northern territories, knew China by this name and the Russians through contact with them introduced it into Europe. The Russians and the peoples of central Asia still know China as Khitai or Kitai. Although in Marco Polo's time all China was under the control of the Great Khan, he limits Cathay to the country north of the Yangtze Valley and calls south China by the separate name of Mangi. The distinction was at that time a real one, since Mangi retained the old Sung culture practically undiluted while Cathay bore the impress of the Tartar Conquest (see CHINA). In the 16th century, however, when European navigators following the sea-route via the Spice Islands reached Far Eastern waters it was Mangi which they knew as China and Cathay was understood as lying away to the north of it and to be reached by a still undiscovered sea-route. Hence ensued the search for the north-west and north-east passages from Europe to the renowned Cathay. This dualism corresponds to the much earlier distinction apparent in Roman literature between the Seres—the Chinese as approached by the overland route—and the Sinae—the Chinese as approached by the sea-route from the south. It was not until the early 17th century that the identity of the country and of the people reached by the two routes was realized.