By the middle of the sixteenth century, Europeans had made themselves aware of the broad outlines of the Continents of Asia, Africa and America. Two hundred years later many of the most striking facts of the geography of the great land-masses had been revealed. In Asia, Siberia had been traversed, China mapped, and Tibet visited, while a vigorous trade was maintained with all the countries of the Eastern Seas. Most of the coast and many of the great lakes and rivers of the Americas had been charted, and flourishing European communities established from Lima to Quebec. Far more was known of Africa than its coastline: a large part of Ethiopia had been visited during the era of Portuguese influence at the beginning of the seventeenth century; Catholic missionaries had worked in the Eastern Sudan in the first decade of the eighteenth century; the Moorish geographers, Idrisi and Leo Africanus, both of whose works were constantly used by European cartographers, provided a succinct account of the citier and states of the Sahara and the Sudan; on the Upper Senegal the French had by 1750 successfully maintained for half a century a trading post over four hundred miles from the sea; in Southern Africa individual adventurers had penetrated deep into the hinterland of the Portuguese colonies in Angola and Mozambique, and of the Dutch settlement at the Cape.