In June 1768, he arrived at
Alexandria, having resolved to endeavour to discover the source of the
Nile, which he believed to rise in Ethiopia. At
Cairo, he gained the support of the
Mamluk ruler,
Ali Bey. After visiting
Thebes, where he entered the tomb of
Ramesses III,
KV11, he crossed the desert to
Kosseir, where he embarked in the dress of a Turkish sailor. After an extensive navigation of the Red Sea in a local vessel, he reached
Jidda in May 1769, and after a stay in
Arabia he recrossed the
Red Sea and landed at
Massawa, then nominally in possession of the Turks, but actually controlled by the local
Na'ib, on 19 September. He reached
Gondar, then the capital of Ethiopia on 14 February 1770, where he was well received by the
Emperor Tekle Haymanot II, Ras
Mikael Sehul, the real ruler of the country, Weizero Aster, wife of the Ras (whom Bruce calls "Esther"), and all Ethiopians generally. His fine presence (he was 6-foot 4 inches high), his knowledge of Ge'ez, his excellence in sports, his courage, resource and self-esteem, all told in his favour among a people who were in general distrustful of all foreigners. he reached
Gish Abay, the source of the
Lesser Abay. When they reached the springs at Gish, James Bruce celebrated his achievement, by picking up a half coconut shell he used as a drinking cup, filling it from the spring, then obliged Strates to drink a toast to "His Majesty King
George III and a long line of princes", and another to "Catherine, Empress of all the Russians" – this last was a gesture to Strates' Greek origin, since
Catherine the Great was just then
at war with the Turks in the Aegean Sea. More toasts followed. Though admitting that the
White Nile was the longer stream, Bruce was the first European to argue that the Blue Nile (which supplied most of its water) was the Nile of the ancients—and thus its source. Páez had described
Lake Tana as the source of the Blue Nile in his two-volume
História da Ethiópia ("History of Ethiopia"). The same location had been visited and speculated about in a similar vein in 1629 by the Portuguese Jesuit missionary
Jerónimo Lobo, who like Páez had arrived in Ethiopia by the Red Sea route. Bruce's journey proved this theory about the source of the Blue Nile to be fact but he disputed the historicity of Páez's visit because Lobo had failed to mention it. Bruce suggested that the relevant passage in Páez's memoirs had been fabricated by
Athanasius Kircher, a Jesuit who had spread the news of Páez's discovery in Europe in 1664. Bruce also sought to discredit the writings of Lobo, joking that he seemed to be able to sail on land and denying the existence of a
spitting cobra described by him. However, more recent research has shown that Lobo's description of the source was correct in its details. ==His return==