Display 2: Quadrant
From the 13th century onward, the quadrant was used in Europe to measure the height of mountains and buildings on land. The instrument consisted of a quarter circle with a plumb line and allowed for precise angle readings.
In the 14th century, the quadrant gained a new application at sea. Portuguese navigators used it to determine their latitude during north-south voyages. This was done by measuring the altitude of the North Star, and later also by observing the noontime altitude of the sun, taking the seasons into account.
The marine quadrant was simple in design. A celestial object was "shot" through a sighting device or two viewing ports, while a plumb line indicated the angle. In practice, however, the instrument proved to be inaccurate: the ship's rolling made it difficult to keep the plumb line steady during the measurement.
In the 15th century, quadrants were further developed into so-called horological quadrants, which, in addition to angles, could also be used to determine the time of day. Thus, the quadrant became a versatile tool for navigation, geometry, and timekeeping.
2.2
Instructie der Zee-Vaert door de Gheheele Werelt, 2th edition 1610
Maker:
Jan Vanden Broek, Rotterdam
Collection:
NavigArte
Books such as Vanden Broek’s work provided a foundation in navigation and a practical guide to the use of maritime instruments, such as the quadrant shown here. They were essential for seafarers in the early 17th century, when the Dutch East India Company (VOC) was expanding toward Southern Africa and Asia.
2.3
Marine quadrant, 1750
Maker:
George Adams, London
Collection:
NavigArte
Signed marine quadrant with the inscription:
“G. Adams, Mathematical Instrument Maker to His Majesty, Fleet Street, London.”
This is one of the earliest forms of the navigation quadrant, without sight vanes, but with a hand-engraved arc graduated from 0 to 90 degrees, subdivided into quarter degrees or 15 arc minutes.
2.4
Gunter quadrant, 1752
Maker:
Edmund Gunter, Welsh, UK
Collection:
NavigArte
English boxwood Gunter or hour quadrant.
Graduated for the latitude of London (52°), with a shadow square indicating positions for five stars, an hour scale, a degree scale, and equinox dates aligned according to the Gregorian calendar. Edge sight vanes are located on the right-hand side.
2.7
Replica portolan manuscript on parchment of the Mediterranean Sea Ca. 1620
Maker:
Placido Caloiro e Oliva (Attributed), Sicilië
Collection:
NavigArte
The portolans are hand-drawn maps that accentuate the coastlines with harbors and bays. Usually they depict the Mediterranean; sometimes they show Europe or the world. This specimen has several compass roses and compass lines or 'rhumb lines'.
Because of the light sensitivity, we cannot show the real parchment portolan here.
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