Water Clock from Fez: photo of a model in an Instanbul museum

Constructed in 1362 it was used by the astronomer of the Qarawayin Mosque in Fez who was in charge of calculating prayer times. The water flow was calculated to remain uniform over 24 hours. The sinking float in the basin causes a pointer to move every four minutes. This in turn results in two carriages with balls, one indicating four minute intervals, the other hourly intervals dropping balls into ringing bowls. Every hour a door behind one bowl also opens.
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