Die «Elefantenuhr» (The «Elephant Clock»)

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The Elephant clock was a model of water clock invented by the medieval Muslim engineer Ismāʿīl al-Jazarī (1136–1206). Its design was detailed in his book, The Book of Knowledge of Ingenious Mechanical Devices (Kitāb fi maʿrifat al-ḥiyal al-handasiyya). 

The clock was a medieval automaton in the form of a life-size replica of an elephant that displayed time with the aid of a water clock. The mechanical elements and figures of the automaton were housed in the howdah (Arabic: hawdaj), a sedan chair on the elephant's back. The clock was designed so that the figures moved, and sounds were emitted every half hour. This invention forms part of the early history of robotics. At the same time, the integration of various cultural elements illustrates the broad geographical spread of Islamic rule during Al-Jazarī's lifetime. 

How the Clock Worked 

The mechanism of the machine is controlled by a water clock inside the elephant.  

In a large cavity filled with water, there is a bowl that continuously fills with water through a small opening in the bottom, causing it to sink. The bowl is connected by a wire to the figure on the elephant's back, which continuously rotates as a result. This figure represents a scribe and indicates the minutes with its quill. Another wire connects the bowl to a basket in the canopy of the palanquin, which contains metal balls. After half an hour, the container has sunk far enough to trigger a lever mechanism. The mechanical bird on the canopy begins to sing, another figure moves its hands, and a metal ball is released from the basket. The ball continues to turn the hour disc on the canopy before falling from a falcon's head into the mouth of a snake, causing it to tip over. The snake's rotating movement pulls the sunken bowl out of the water and empties it. The ball then falls into a vase and the mahout (elephant driver sitting at the front) strikes a cymbal. The snake then swings back into place and the process repeats itself as long as there are still balls in the basket. The basket must be refilled twice a day. 

Another innovative feature of the clock was how it recorded the passage of temporal hours, which meant that the rate of flow had to be changed daily to match the uneven length of days throughout the year. To accomplish this, the clock had two tanks. The top tank was connected to the time-indicating mechanisms, and the bottom was connected to the flow control regulator. At daybreak, the tap was opened and water flowed from the top tank to the bottom tank via a float regulator that maintained a constant pressure in the receiving tank.  

Interesting Facts 

The elephant clock was the first clock with an automaton that ran again after a certain period of time. A modern working reproduction of the 900-year old invention can be seen outside the Musée d’Horlogerie du Locle, Château des Monts, in Le Locle, Switzerland.