Hadley's navigational quadrant
Datec 1770
Object number00029267
NameQuadrant
MediumMahogany, boxwood, ivory, brass, glass
DimensionsOverall: 510 x 470 x 75 mm, 0.11 kg
Display Dimensions: 509 x 425 x 73 mm
Display Dimensions: 509 x 425 x 73 mm
ClassificationsTools and equipment
Credit LineANMM Collection
DescriptionNamed because its arc represents a quarter of a circle (from Latin quadrans), a quadrant is an instrument of double reflection and by means of two mirrors is capable of measuring angles up to 90 degrees. This quadrant is thought to have been made in about 1770.HistoryIn 1731, John Hadley described what is now known as a quadrant, to the Royal Society of London. He obtained a British patent in 1734 and as a result, quadrants are sometimes referred to as Hadley quadrants. The earliest examples of quadrants date to around 1460. They were often large and difficult to use and were limited in their accuracy.
After details of Hadley's new patented quadrant were announced, the Admiralty ordered a series of tests to be conducted, and as a result of these Hadley's quadrant became widely accepted. The quadrant remained in common usage until replaced by the more accurate sextant toward the end of the 18th century.
SignificanceThis quadrant is typical of instruments used by navigators for determining latitude during the 18th century.
19th century
mid-18th century
Early 19th century
1780-1850
