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The Nautical Collection of P. C. Laskaridis
Magnetic compass manufactured by Dent
Date: 19th-century
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In a ship, the gyroscopes, the ship’s compasses, the stoves, and even the beverage cases use such suspension systems in order to remain upright in relation to the horizon as the boat tilts.

This suspension mechanism, which is used for the compasses, is called Cardano-type suspension, and has been named after the Italian mathematician and physicist Gerolamo Cardano (1501-1576), who described it in detail. The appliance, however, is known since antiquity as it was described for the first time in the 3rd century b.C. by Philo of Byzantium.

The magnetic compass was the instrument that provided important boost to shipping since it allowed a relatively accurate course to be followed, day and night, without relying on visible points of land or constellations at night.

The compass contains a reading disk, the anemometer, with subdivisions and symbolisms. This anemometer incorporates the magnetic needle of the compass and rotates with it.

There are peripheral and quaternary anemometers, subdivided in angle-measuring-radians, degrees, rhombuses, and so on. More specifically, the anemometer is a disk that represents the horizon, the circumference of which is subdivided from 0° to 359° and has two vertical diameters, the one of which points to the meridian line with N (North) and S (South) as the edge points of the horizon; and the other (points to) the line of the first vertical (diameter) with E (East) and W (West) as the edge points of the horizon.

In 1890 the British Admiralty asked four manufacturers (Lilley, Reynolds, Hughes and Dent) to submit a boat compass suitable for both steam and sails. The model Dent offered was a liquid-type compass; in other words, the disk of the anemometer, instead of resting on a vertical axis, floated freely in liquid (alcohol) reducing friction to minimum and achieving in this way maximum precision. The Dent-type compass prevailed over that of Lord Kelvin, which was dry-type, that is without liquid, and was applied to British ships since 1892, remaining in service until the end of the World War I.

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