He soon set out for Spain, and worked his way through Morocco, across the Sahara, to the Soudan. He travelled along the Niger (which he took for the Nile), and visited Timbuctoo. He ultimately returned to Fez in 1353, twenty-eight years after he had set out on his travels. Their chief interest is in showing the wide extent of Islam in his day, and the facilities which a common creed gave for extensive travel. But the account of his journeys was written in Arabic, and had no influence on European knowledge, which, indeed, had little to learn from him after Marco Polo, except with regard to the Soudan. With him the history of mediæval geography may be fairly said to end, for within eighty years of his death began the activity of Prince Henry the Navigator, with whom the modern epoch begins. Meanwhile India had become somewhat better known, chiefly by the travels of wandering friars, who visited it mainly for the sake of the shrine of St. Thomas, who was supposed to have been martyred in India. Mention should also be made of the early spread of the Nestorian Church throughout Central Asia. As early as the seventh century the Syrian Christians who followed the views of Nestorius began spreading them eastward, founding sees in Persia and Turkestan, and ultimately spreading as far as Pekin. There was a certain revival of their missionary activity under the Mongol Khans, but the restricted nature of the language in which their reports were written prevented them from having any effect upon geographical knowledge, except in one particular, which is of some interest. The fate of the Lost Ten Tribes of Israel has always excited interest, and a legend arose that they had been converted to Christianity, and existed somewhere in the East under a king who was also a priest, and known as Prester John. Now, in the reports brought by some of the Nestorian priests westward, it was stated that one of the Mongol princes named Ung Khan had adopted Christianity, and as this in Syriac sounded something like "John the Cohen," or "Priest," he was identified with the Prester John of legend, and for a long time one of the objects of travel in the East was to discover this Christian kingdom. It was, however, later ascertained that there did exist such a Christian kingdom in Abyssinia, and as owing to the erroneous views of Ptolemy, followed by the Arabs, Abyssinia was considered to spread towards Farther India, the land of Prester John was identified in Abyssinia. We shall see later on how this error helped the progress of geographical discovery.