18th Century Maritime Hourglass | 30 Seconds Timer

Hand-Blown Glass, Original Wood Frame, Nautical Navigation Instrument
Height: 12.5 cm | European origin, circa 1750–1800

An exceptionally rare and authentic 18th-century maritime sandglass, purpose-built for use at sea as a 30-second log timer — a vital navigational tool during the golden age of sail. This piece would have been used aboard naval or merchant vessels to measure short time intervals for calculating a ship's speed using the traditional log line method — the very origin of the term "knots" in nautical speed.

• Structure: Cylindrical frame constructed from turned hardwood, darkly patinated with age. The frame is secured with four vertical wooden supports and retains visible tool marks and age wear.

• Top & Base: Wood disks joined with early iron pins or nails, now oxidized. One end displays handwritten numeric marks, likely shipboard inventory or identification.

• Glass Bulbs: Two joined hand-blown hourglass vessels, sealed at the neck with a characteristic natural fiber cord wrapping, likely sinew or hemp — typical of 18th-century maritime rigging materials.

• Sand: Fine, pale sand with irregular granularity, consistent with period maritime hourglasses.

• Condition: Structurally sound and complete. Shows signs of use and age including minor surface losses, oxidation to iron elements, and historic wormholes — long inactive, serving to reinforce the age and authenticity of the piece.

This timer was used to measure 30-second intervals at sea. Sailors would throw a weighted log overboard attached to a rope knotted at regular intervals. The sandglass was inverted and, during its run, the number of knots paid out indicated the ship’s speed in nautical miles per hour.

This rudimentary yet effective system remained a mainstay of maritime navigation from the 16th to the early 19th century. Today, such sandglasses are prized by collectors of nautical instruments, early scientific tools, and museum-quality maritime antiques.