This is a replica of an ingenious Song dynasty clepsydra (water clock). Actually there was never water clock in the tower, so the replica here is simply a display piece for the modern visitor. The clock was regulated by the flow of water between the three buckets arranged in a "staircase" on top of the device. A cylinder, seen to the right, holds a level stick which indicated the time according to the water level inside the cylinder. The figure to the left, actuated by an overflow mechanism (tipping bucket), clashed its cymbals every quarter hour.