61. For the identity of Virtha and Tecrit, see d'Anville,
Geographie Ancienne, tom. ii. p. 201. For the siege of that
castle by Timur Bec, or Tamerlane, see Cherefeddin, 1. iii.
c. 33. The Persian biographer exaggerates the merit and
difficulty of this exploit, which delivered the caravans of
Bagdad from a formidable gang of robbers.