Napoleon III glass and brass hourglass

Elegant glass and brass hourglass with wax bow and leaf decoration.
Duration 25 min.

to know the duration of an event
The hourglass is simply a clepsydra that flips over to refill the container in a simple way: by turning it upside down.
The oldest hourglass has been dated to the reign of Amenophis III, around 1400 BC.

In France, it was invented by a Chartres monk in the 8th century.

The length of time an hourglass will run does not necessarily depend on its size. However, if the flow is expected to last several days, or even weeks, it should be sized accordingly.

Contrary to what their name might suggest, hourglasses do not contain ordinary sand, but a mixture of calcined marble powder, eggshell and lead or zinc.