This sentence is out of place, and should follow the sentence in the preceding paragraph which speaks of the Sultan Al-Habash.
Kutz, the present Kus, is halfway between Keneh and Luxor. The old town, now entirely vanished, was second in size to Fostat, and was the chief centre of the Arabian trade. The distance of Kus from Fayum is about 300 miles. The letter
letter 'Sin' denotes 300, not 3.
In the Middle Ages the Fayum was wrongly called Pithom. E. Naville has identified the ruins of Tell-el-Maskhuta near Ismailieh with Pithom, the treasure city mentioned in Exodus i. 11. Among the buildings, grain-stores have been discovered in the form of deep rectangular chambers without doors, into which the corn was poured from above. These are supposed to date from the time of Rameses II. See The Store City of Pithom and the Route of the Exodus: A Memoir of the Egypt Exploration Fund. E. Naville, 1885. The Fayum, or Marsh-district, owes its extraordinary fertility to the Bahr Yussuf (Joseph's Canal).
The Arab story is that when Joseph was getting old the courtiers tried to bring about his disgrace by inducing Pharaoh to set him what appeared to be an impossible task, viz. to double the revenues of the province within a few years. Joseph accomplished the task by artificially adapting a natural branch of the Nile so as to give the district the benefit of the yearly overflow. The canal thus formed, which is 207 miles in length, was called after Joseph. The storehouses of Joseph are repeatedly mentioned by Arabic writers. Cf. Koran xii. 55, Jacut, IV, 933 and Makrizi, I, 241.