8. Ducas. Hist. c. 34 [p. 136, ed. Paris; p. 108 ed. Ven.;
p. 242, ed. Bonn]. Leunclavius Hist. Turcica Mussulmanica,
1. xv. p. 577. Under the Greek empire these castles were
used as state prisons, under the tremendous name of Lethe,
or towers of oblivion.