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Close-up: Hourglass The hourglass is based on a fairly simple concept, but was very useful long ago and is still used today. The sand in the hourglass solves several problems of the clepsydra: it does not freeze in cold temperatures, it does not evaporate in warm weather, and it can be sealed so nothing can get in that will affect the flow of the sand in the glass. You can learn how to make a simple hourglass in the hands-on section of this site! |
