28 Second Hour Glass for Hand Log – ca. 1850
The hand log was first described in 1574 (Sharp, p 5). It consists of a wooden chip with peg, the log line, a reel and a 28 (long) or 14 second (short) sandglass. The chip in the shape of a circle sector and weighted with lead, is fitted with two lines to the peg, the end of the log line forms the third. After a stray line of about thirty meters, the log line is equally divided into parts of 23 feet 9 inches (7.20 meters) to start with a flag or bunting. Thus at every 47 feet 3 inches knots are placed to denote the number of miles. The chip is thrown astern of the ship and remains static whilst the line is paid out and the ship sails away from it. The number of knots sailed out in 28 or 14 seconds indicates the speed of the ship in miles per hour or knots. Using the short glass doubles the number of knots counted.
Date: ca. 1850
HD reel: 96 x 62 mm
Signed: not signed
Condition: 28 seconds, complete and in working condition