Hourglass
Reloj de arena
- Date
- 1338 · confidence medium
- Place
- Siena, Tuscany, Italy
- Credited to
- Unknown (earliest image: Ambrogio Lorenzetti)
- Field
- Knowledge & symbols
⚠️ Disputed: the sources disagree.
What it is
Two glass bulbs joined by a narrow neck through which sand falls in a fixed time, used to measure intervals rather than the time of day. The earliest sure depiction is Lorenzetti's Good Government fresco in Siena (1338), where Temperance holds one.
The legend of a monk Luitprand at Chartres cathedral (8th century) is unsupported; hourglasses are known in the 14th century, but blown-glass ampoules may be somewhat earlier and the author is unknown.
What it led to
- timing of sermons, lectures and watches
- timing in laboratories and kitchens
- shipboard hourglass and log line