Anaphoric water clock

The capacity to convert converting linear motion (in the lower basin) into circular motion (on the clock dial) was soon put to even more sophisticated use by the Greeks. Here the simple dial marked with 24 hours was replaced with a circular disc picturing the constellations which rotated around once in the course of a day. As the wheel turned, the constellations passed by a metal wire representing the horizon. This way the clock showed at a glance which constellations were rising and setting, even during daytime. A video animation provides a clearer impression of the function of this clock.

A clock of this type was housed in Athens in the Tower of the Winds (image 2), an eight-sided marble building constructed around 50 BC. Each side of the octagon featured its own sundial facing one of the eight wind directions.

Even more complicated clocks used water flow to power mechanical and audible signals. A reconstructed Greek example can be studied here. 

Commentary. Philipp Nothaft (May-June 2019) and Howard Hotson (May 2021)