Leonardo da Vinci designed a water clock to measure equal hours.
His hydraulic clock studies used the controlled movement of water to measure time. In one design, water gradually filled a vessel, and the rising level triggered a mechanism that could indicate elapsed intervals. Leonardo also explored systems of floats, gears, and alarms to make the display or signal more automatic.
Water clocks were ancient devices long before Leonardo. Their accuracy depended on controlling the flow and accounting for changes in water pressure, vessel shape, and temperature. Leonardo’s contribution was not the invention of the water clock itself, but the detailed refinement of its mechanisms during his broader investigations of hydraulics and timekeeping.
This work should not be confused with the pendulum clock, which was developed much later. Galileo studied pendulum timekeeping in the seventeenth century, and Christiaan Huygens built the first practical pendulum clock in 1656. Leonardo’s clock research remained mechanical and hydraulic.