EXHIBITS > Measuring instruments, tools and machines of the ancient Greeks >
Mechanism for accurate measurement of sea distance.
It consisted of a box with co-operating gearwheels and an endless screw connected to a hydrokinetic winged wheel. The periphery of the wheel inside the wings touched sea level. The box was placed either on a float drawn by the ship or on the ship's internal sidewall with the wheel shaft penetrating the inner sidewall. The wheel rotated according to the speed of the ship. A calibrated disc (within the box), embedded on the shaft of the last gearwheel, indicated the distance travelled.
SOURCES: "Heron of Alexandria, On dioptra"