It must have been between 1160 and 1209 that he held this position; but the date at which he lived and wrote cannot be more accurately determined.
The average speed is obtained very accurately from solar and stellar observations for the position of the ship. The difference between the speed of the ship and the rate of paying out gives the amount of.
27 9) that the inhabitants of Colchis whom, like Herodotus (ii., 104) he looks upon as the descendants of Egyptian colonists, preserved, as heirlooms, certain graven tablets (Kbp(€ls) on which land and sea, roads and towns were accurately indicated.
851) which accurately represents the view entertained of this people by mariners down to modern times.
In 1757 he presented a telescope to the king, so accurately driven by clockwork that it would follow a star all night long.