At Cazembe's he found an old white-bearded half-caste named Mohammed bin Sali, who was kept as a kind of prisoner at large by the King because of certain suspicious circumstances attending his advent and stay in the country. Through Livingstone's influence Mohammed bin Sali obtained his release. On the road to Ujiji he had bitter cause to regret having exerted himself in the half-caste's behalf. He turned out to be a most ungrateful wretch, who poisoned the minds of the Doctor's few followers, and ingratiated himself with them by selling the favours of his concubines to them, by which he reduced them to a kind of bondage under him. The Doctor was deserted by all but two, even faithful Susi and Chumah deserted him for the service of Mohammed bin Sali. But they soon repented, and returned to their allegiance. From the day he had the vile old man in his company manifold and bitter misfortunes followed the Doctor up to his arrival at Ujiji in March, 1869. From the date of his arrival until the end of June, 1869, he remained at Ujiji, whence he dated those letters which, though the outside world still doubted his being alive, satisfied the minds of the Royal Geographical people, and his intimate friends, that he still existed, and that Musa'a tale was the false though ingenious fabrication of a cowardly deserter. It was during this time that the thought occurred to him of sailing around the Lake Tanganika, but the Arabs and natives were so bent upon fleecing him that, had he undertaken it, the remainder or his goods would not have enabled him to explore the central line of drainage, the initial point of which he found far south of Cazembe's in about latitude 11 degrees, in the river called Chambezi. In the days when tired Captain Burton was resting in Ujiji, after his march from the coast near Zanzibar, the land to which Livingstone, on his departure from Ujiji, bent his steps was unknown to the Arabs save by vague report. Messrs. Burton and Speke never heard of it, it seems. Speke, who was the geographer of Burton's Expedition, heard of a place called Urua, which he placed on his map, according to the general direction indicated by the Arabs; but the most enterprising of the Arabs, in their search after ivory, only touched the frontiers of Rua, as, the natives and Livingstone call it; for Rua is an immense country, with a length of six degrees of latitude, and as yet an undefined breadth from east to west. At the end of June, 1869, Livingstone quitted Ujiji and crossed over to Uguhha, on the western shore, for his last and greatest series of explorations; the result of which was the further discovery of a lake of considerable magnitude connected with Moero by the large river called the Lualaba, and which was a continuation of the chain of lakes he had previously discovered.