Device to measure time using gravity to make sand flow through a small opening in the middle. Its shape is usually that of two funnels connected at their small openings. If the sand has gone down from the upper part to the lower part, you know a certain amount of time has gone by (for instance 3 minutes for an hourglass used for soft-cooked eggs). To start measuring time again one has to turn around the hourglass.

Hour"glass` (?), n.

An instrument for measuring time, especially the interval of an hour. It consists of a glass vessel having two compartments, from the uppermost of which a quantity of sand, water, or mercury occupies an hour in running through a small aperture unto the lower.

⇒ A similar instrument measuring any other interval of time takes its name from the interval measured; as, a half-hour glass, a half-minute glass. A three-minute glass is sometimes called an egg-glass, from being used to time the boiling of eggs.<-- also = egg timer -->


© Webster 1913.

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