Marine sandglass
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A marine sandglass is a timepiece of simple design that is a relative of the common hourglass, a marine instrument known since the 14th century. Sandglasses were used to measure the time at sea or on
1859 Helmsman's marine sandglass, in a four-column wood stand
Sarcophagus dated ca 350 AD, representing the wedding of Peleus and Thetis (Wincklemann: observe the magnification with the hourglass held by Morpheus in his hands)
Temperance bearing an hourglass; detail Lorenzetti's Allegory of Good Government, 1338
Dotzè del Crestià (Valencia – 1484)
Chip log
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A chip log, also called common log, ship log, or just log, is a navigation tool mariners use to estimate the speed of a vessel through water. The word knot, to mean nautical mile per hour, derives fro
Marine sandglass
…to measure the time at sea or on a given navigational course, in repeated measures of small time increments (e.g., 30 minutes). Used together with the chip log, smaller marine sandglasses were also used to measure the boat speed through the water in knots. Although vital to maritime navigation, marine sandglasses…
Model of chip log and associated kit. The reel of log-line is clearly visible. The first knot, marking the first nautical mile is visible on the reel just below the centre. The timing sandglass is in the upper left and the chip log is in the lower left. The small light-coloured wooden pin and plug form a release mechanism for two lines of the bridle. From the Musée de la Marine, Paris.
Chip log in the 18th century
Taffrail Log Rotator
Negus Taffrail Log