Staithes Museum's replica of the Harrison Clock At Staithes Museum, we often think of Captain Cook’s voyages as the height of 18th-century maritime exploration — voyages that depended not only on courage and seamanship but also on advances in navigation. Among the most pressing questions of the age was how to find a ship’s longitude at sea — a problem so difficult it spawned a royal reward and centuries of effort. Most people have heard of John Harrison’s marine timekeepers.