Set of four sand glases, c 1720.
© Science Museum / Science & Society Picture Library
This set of sand glases in an ornate mount of ebony and ivory is probably Italian. The glases are marked 1/4, 2/4, 3/4, and 4/4 with time intervals indicated by the appropriate number of ivory studs set above and below each glas on the enclosing panels, each stud representing 1/4 hour. Sand glases were particularly useful in ships, as they are relatively unaffected by the motion of a ship and by violent weather conditions.