<P> Owing to their failure to penetrate the sudd wetlands of South Sudan, the upper reaches of the Nile remained largely unknown to the ancient Greeks and Romans . Various expeditions failed to determine the river's source . Agatharcides records that in the time of Ptolemy II Philadelphus, a military expedition had penetrated far enough along the course of the Blue Nile to determine that the summer floods were caused by heavy seasonal rainstorms in the Ethiopian Highlands, but no European of antiquity is known to have reached Lake Tana . </P> <P> The Tabula Rogeriana depicted the source as three lakes in 1154 . </P> <P> Europeans began to learn about the origins of the Nile in the 15th and 16th centuries, when travelers to Ethiopia visited Lake Tana and the source of the Blue Nile in the mountains south of the lake . Although James Bruce claimed to be the first European to have visited the headwaters, modern writers give the credit to the Jesuit Pedro Páez . Páez's account of the source of the Nile is a long and vivid account of Ethiopia . It was published in full only in the early 20th century, although it was featured in works of Páez's contemporaries, including Baltazar Téllez, Athanasius Kircher and by Johann Michael Vansleb . </P> <P> Europeans had been resident in Ethiopia since the late 15th century, and one of them may have visited the headwaters even earlier without leaving a written trace . The Portuguese João Bermudes published the first description of the Tis Issat Falls in his 1565 memoirs, compared them to the Nile Falls alluded to in Cicero's De Republica . Jerónimo Lobo describes the source of the Blue Nile, visiting shortly after Pedro Páez . Telles also used his account . </P>

Who discovered the source of the nile river