The situation of the fortress, and the topography of the Bosphorus, are best learned from Peter Gyllius (de Bosphoro Thracio, l. ii. c. 13), Leunclavius (Pandect. p. 445), and Tournefort (Voyage dans le Levant, tom. ii. lettre xv. p. 443, 444); but I must regret the map or plan which Tournefort sent to the French minister of the marine. The reader may turn back to chapter 17 of this History.