Hourglass
An hourglass is a device typically consisting of two glass bulbs connected by a narrow neck, containing sand that takes a specific amount of time to flow from the upper bulb to the lower bulb. It is used as a traditional timekeeping instrument or as a symbol of the passage of time.
External Links
- [Hourglasses.com] Welcome hourglasses.com - BlueHost.com
- [Hourglass.us]
- [hourglass-telescope-mirrors.com] Home - Dobsonian Telescopes Mirror Making, by Lonnie Robinson
- [thesidewayshourglass.com] the sideways hourglass
- [brhg.net] Bloodred Hourglass | Melodic Metal |Finland