A klepsydra is a kind of glass that measures time using the flow of water, rather than sand. In this 30-minute glass, water flows through four glass tubes with curved ends which pass through the cork seal between the ampoules. The inner tubes allow the water to flow down, while the outer tubes let air flow back into the upper bulb. The glass is in a wooden frame with five supports and foliate decoration painted in gold and vermillion. It has a dome which can be removed and attached to either end of the frame so that the glass can be turned upside-down and reset. The vane from the top of the dome is missing.