Italian astronomer Galileo Galilei competed for two longitude prizes in the 17th century.
Credit: Smithsonian Institution Libraries

Early Sea Clock Experiments

Prizes offered by Spain in 1598 and the Dutch Republic two years later stimulated the best scientific minds of the day to build better clocks for finding position at sea.

The challenge was enormous. At that time, no clock—on land or sea—could keep better time than within about 15 minutes a day. But after nearly two centuries, with the invention of the chronometer, accuracy at sea improved to about 1/5th of a second a day.

“One [method of finding longitude] is by a Watch to keep time exactly. But, by reason of the motion of the Ship, the Variation of Heat and Cold, Wet and Dry, and the Difference of Gravity at different Latitudes, such a watch hath not yet been made.” —Sir Isaac Newton, 1714

This is a replica of Galileo's design for a pendulum clock. In 1642, for a Dutch longitude prize, Galileo proposed both an astronomical solution and an accurate sea clock—the first clock ever to have a pendulum. Galileo died before making the clock, but his son built a model in 1649.
In pursuit of a sea clock, Christiaan Huygens, a mathematician from the Netherlands, changed timekeeping forever. He patented the first working pendulum clock in 1656 and later devised a watch regulator called a balance spring. These inventions became standard components for keeping good time. Pendulum clocks immediately became the best timekeepers for use on land. But several sea trials demonstrated to Huygens that the pendulum clock would never work accurately on a heaving ship’s deck.
This clock was made by Johannes van Ceulen around 1680. After Christiaan Huygens demonstrated the feasibility of the pendulum for regulating a clock, wealthy homeowners developed a taste for pendulum clocks. Huygens worked with several Dutch clockmakers, including his neighbor Johannes van Ceulen, who made this table clock. It is one of the earliest clocks with a pendulum.