Sand glass

A sand glass is an instrument which makes it possible to measure an interval of Temps. Although one does not know exactly when the sand glass was invented, its use is proven as from the 14th century. In the beginning it consisted of two bulbs of Verre placed one on the other and connected by a fine pipe. Progress of the blowing of glass made it possible thereafter to carry them out of only one part. The bulb filled of fine Sand, or a similar body, is placed in top and by the effect of the Gravité, sand runs out slowly and regularly in the other. Once all sand is in the bulb of bottom, one can turn over the sand glass to measure another period of time.

In general, the common sand glasses run out their sand into 1 or 5 minutes. A current and familiar use is the control of the cooking of boiled eggs with some 3 minute old sand glasses. The sand glass is as used in the board games to measure time as a player puts at mimer, to play, draw… Autrefois it was used on the boats to measure the quarters of day before.

The sand glass is not a reliable tool to measure the flow of time precisely: factors can affect the duration of flow of sand: the smoothness of sand, the shape of the bulbs, the size of the tube which connects them, its wear by the flow of sand, the more or less horizontal position… If one measured with a precise electronic chronometer time that puts sand to run out from one bulb to another, one could surely note that time is never exactly the same one.

Symbolic system

The sand glass represents the time which passes. It is sometimes represented with wings of bird or bald person mouse to symbolize the fugacity of the time which passes. The Allegory S of Time or Death often carry a sand glass.

See too

Clepsydre

Simple: Hourglass

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