This section is from "The Domestic Encyclopaedia Vol2", by A. F. M. Willich. Amazon: The Domestic Encyclopaedia.
Hour-Glass, a kind of chro-nometer, employed by navigators, as well as by some • artisans and mechanics, to measure the passing of time, by means of the descent or running of sand, out of one glass into another.
The best hour-glasses are those which are filled with egg-shells, well dried in an oven, finely pulverized, and sifted; as they shew the passing of time with greater exactness than common sand.
 
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