Marine sand-glass

From Object Wiki

Marine sand-glass
Manufacturer	(unknown)
Production years	19th century
Production location	(unknown)

A nineteenth-century example, of the type used in ships in connection with the hand log for obtaining the speed of the vessel. Its sand passes from the upper to the lower chamber in a period of 14 seconds, and the instrument is inverted when it is again to be used.

[edit] How it works

The timekeeping depends on the regular flow of sand through a small orifice. The time taken for one bulb of the sand glass to empty is a definite interval, at the end of which the glass can be turned over and the process repeated. Sand glasses are useful for measuring long periods of time, but prove inadequate for short time intervals.

[edit] Memories

Do you remember stories about sand glasses? Add your memories.

[edit] In the Science Museum's Records

Inv. No: 1920-360