When determining position in the sea, it is essential to know both one's latitude and longitude.  The former was taken care of by the Astrolabe, but in order to find one's position east and west an accurate clock was needed.  Unfortunately, pendulums (used for most accurate clocks of the day) were unsteady at sea due to the pitching of the ship on water.  Finally, in the late 18th century C.E., a clock was fashioned that would do the trick; it made use of a coiled spring to move the parts consistently and accurately.  With this development, ships could now move across even the widest seas and still be able to know when they could finally disembark!