Sea trials for Huygens pendulum clock.

By 1664, Huygens had all the elements of a theoretical treatise on the pendulum clock. But by then he also had reason to hope that the treatise could offer stunning evidence of the theory’s practical value. In 1663 and 1664 the Royal Society had sent a marine version of the clock to sea to test its reliability and its accuracy as a means of determining longitude. The first results had exceeded expectations.