Sherefeddin only says (l. iii. c. 13) that the rays of the setting, and those of the rising sun, were scarcely separated by any interval; a problem which may be solved in the latitude of Moscow (the 56th degree), with the aid of the Aurora Borealis, and a long summer twilight. But a day of forty days (Khondemir apud D'Herbelot, p. 880) would rigorously confine us within the polar circle.