Ras-el-Ain, probably Rhesaina. The river Khabur—the Araxes of Xenophon—flows from the Kurdistan mountains southwards, and runs into the Euphrates.
The Gozan river cannot be, as tacitly assumed by Asher, the Kizil Uzun (also known as the Araxes). The Kizil Uzun is on the right of the watershed of the mountains of Kurdistan, and falls into the Caspian Sea. The Khabur above referred to flows through Mesopotamia, not through Media. The misconception arises probably from the author being too mindful of the passage occurring repeatedly in Scripture, e. g. 2 Kings xvii. 6: " ... and placed them in Halah and in Habor by the river of Gozan, and in the cities of the Medes."
All the MSS. except BM. have here: "Thence it is two days to the city of Nisibis (Nasibin). This is a great city with rivulets of water, and contains about 1,000 Jews."
Josephus (Antiquities, I, 3) mentions that Noah's Ark still existed in his day. Rabbi Pethachia, who travelled through Armenia within twenty years after Benjamin, speaks of four mountain peaks, between which the Ark became fixed and from which it could not get free. Arab writers tell us that Jabal Judi (Koran, ch. xi, ver. 46) with the Mosque of Noah on the summit, could be seen from Geziret. See also Marco Polo, Bk. I. ch. 3.
See Lebrecht's Essay "On the State of the Caliphate at Bagdad." Sin-ed-din, otherwise known as Seif-ed-din, died 1149, some twenty years before Benjamin's visit, and Graetz (vol. VI, note 10) suggests that the appointment of Astronomer Royal must have been made by Nur-ed-din's nephew. None of the MSS. have this reading, nor is such a correction needed. R. Joseph may have been appointed by Nur-ed-din's brother, and would naturally retain the office during the reign of his successor.