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[[Image:2699.jpeg|right|thumb|200px]]
[[Image:2699.jpeg|right|thumb|200px]]
An '''hour glass''' is a [[time]]-keeping device.
An '''hour glass''' is an obsolete [[time]]-keeping device. It is made up of two bulbs connected by a narrow passage, through which sand flows at a given rate. Hourglasses were probably invented in [[Alexandria]], [[Egypt]] between 200 and 300 A.D. <ref>
{{Cite book
| publisher = W. & R. Chambers, Ltd.
| isbn =
| pages =
| last =
| first =
| title = The Book of Days: A Miscellany of Popular Antiquities in Connection with the Calendar
| date =
| year =
}}</ref>. Though they are no longer used for the purpose of keeping time, they are sometimes used in lieu of electronic timers, for example, as egg timers.
==Sources==
{{reflist}}
[[category:technology]]
[[category:technology]]