TitleBrass octant, ‘Geo Wallace’Date1700sAbout this objectAn invention of the early 1730s, this octant was contemporary to the nautical instruments used on L'Astrolabe and La Boussole during Lapérouse’s expedition, providing a glimpse into the development of navigation technology at the time, which played a crucial role in the surveys of uncharted territories by European explorers in the 18th and 19th century. Object No.88.1Physical descriptionThis octant features an A-shaped frame made of ebony, with brass index arm, brass fittings and ivory scales. The brass makers plaque embedded on the crossbar of the octant frame is engraved with the name ‘Geo Wallace’.Inscriptions & marksGeo Wallace' DimensionsH: 40cm
W: 33cm
D: 8.5cmPlace madeEnglandMaterialBrassEbonyIvorySourceLa Perouse MuseumProvenance 18th c. - produced;
prior to 1988 - owned by the Crown in Right of the State of New South Wales;
1988 - donated to La Perouse Museum by the Laperouse Association for the Australian BicentenaryCredit lineGift of Laperouse Association for the Australian Bicentenary, 1988Acquisition date1988On displayYesTypeMuseum objectsOrganisations (Detailed entries)La Perouse Museum (La Perouse, N.S.W.)Production notesThe octant forms an angle of 45 degrees, one eighth of a circle, hence its name. It was used to measure the altitude (the angle between the sun, the moon or another celestial body above the horizon) up to 90 degrees, which then helped determine a ship’s latitude. The ability to measure large angles made it especially useful for celestial navigation at sea, beyond the sighting of landmarks, providing a more accurate estimation of the ship’s coordinates.
The octant was invented concurrently in the 1730s by John Hadley (1682–1744), an English mathematician, and Thomas Godfrey (1704–1749), a glazier in Philadelphia. While both have legitimate claim to the invention, Hadley generally received the greater share of the credit. This may be due to England’s prominence as a centre for instrument-making, supported by the Royal Society and new manufacturing techniques. Instrument makers like Hadley established workshops in major cities with trading ports such as London and Liverpool. It is also worth noting that before them, the English polymath Robert Hooke showed a reflecting quadrant to the Royal Society in 1670, and Isaac Newton later showed another and read a paper on it. Newton’s work in optics and physics would have laid the groundwork for the development of instruments like the octant.
Ebony is a common material for octants, chosen for its resistance to dimensional change under the varied temperature and humidity conditions that instruments are exposed to at sea. Bone or ivory was often used for the inlaid scale because it was easy to engrave and resistant to corrosion from the salty sea air.
Reference
https://www.hsm.ox.ac.uk/octant
https://www.ion.org/museum/item_view.cfm?cid=6&scid=13&iid=27ThemesEuropean arrivalsScience and communication
