Marine Sandglass, 34-second

Description
This is an American marine sandglass made during the 19th century, most likely after 1840. It takes approximately 34 seconds for sand to move from the top chamber, through the narrow neck, to the bottom.
At sea, time was crucial to navigation. Since the Middle Ages, mariners had used sandglasses that measured intervals of time to calculate ship speed, distance traveled, and periods of duty.
To determine ship speed, sailors used sandglasses to time the distance run against knots in the log line. The log was a piece of wood, weighted on one side to float upright and attached to a long rope. This log line had knots tied at regular intervals, traditionally seven fathoms (42 feet) or eight fathoms (48 feet), and wound off of a hand-held reel. With the log line cast astern, a seaman counted the number of knots played out in about half a minute to get the approximate speed in “knots,” or nautical miles per hour.
Location
Currently not on view
date made
ca 1840
place made
United States
Measurements
overall: 4 3/4 in x 2 3/4 in; 12.065 cm x 6.985 cm
wood pillars: 4 in x 1/2 in; 10.16 cm x 1.27 cm
glass: 4 in x 1 1/4 in; 10.16 cm x 3.175 cm
ID Number
ME.327538
accession number
266230
catalog number
327538
Credit Line
Gift of Preston R. Bassett
See more items in
Work and Industry: Mechanisms
Measuring & Mapping
Data Source
National Museum of American History, Kenneth E. Behring Center

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