An escapement is a mechanical device found in clocks and watches that helps keep track of time. It converts the energy from a power source, such as a spring or weight, into distinct increments of ticks or beats that keep time. The escapement also serves to prevent the gears found within the escapement from turning too quickly, ensuring that timekeeping operates accurately and consistently. When they were first developed in the 13th century, they began replacing more rudimentary time-keeping devices such as sundials and water clocks. Dutch mathematician and astronomer Christian Huygens introduced the pendulum escapement in 1656 which provided clocks with substantially increased accuracy. The historical significance of escapements extends beyond the science of timekeeping by influencing the fields of engineering and physics through the principles of mechanics and the transfer of energy.

Various types of escapements have been developed over the centuries, each improving precision and reliability in horology. This is a model of an early hairspring escapement by Robert Hooke, an English 17th-century scientist and inventor. He used pig bristle, a natural material, because of its flexibility and resilience. This escapement worked by using a balance wheel attached to a hairspring which would make the wheel oscillate back and forth at a consistent rate. This innovation was significant in horology, but especially in watches. The model was a teaching aid made by William Samelius (1873-1961) who was a master clockmaker and Dean of American Watchmakers at the Elgin Watchmaker’s College in Elgin, Illinois which opened in 1920 and permanently closed in 1960.