Triple circle sextant vernier screw

Manufacturer Henry Hughes & Son Ltd (British, 1828 - 1947)

Date1850-1900

Object number00028241

NameSextant vernier screw

MediumCopper alloy

DimensionsOverall: 13 x 13 x 35 mm

ClassificationsTools and equipment

Credit LineANMM Collection Gift from Dorothy Sharp

Terms

DescriptionThis vernier screw was made by Henry Hughes & Son in the late 19th century, and was issued as an accessory to a triple circle sextant (along with two telescopes, a dark tube, an eyepiece, two eyepiece filters, and two cleaning cloths).HistoryThe sextant is a navigational instrument used to measure vertical and horizontal angles at sea and is an essential instrument in the safe navigation of ships on open water. Developed in the late 1750s from the more primitive quadrant, the sextant could measure up to 120 degrees and was essential for the making of lunar observations in order to calculate a ship's longitude. This vernier screw was manufactured by the well known English instrument maker Henry Hughes and Sons in the late 1800s. Unlike many other English instrument makers, Henry Hughes and Sons - established in 1839 - showed a large amount of commercial acumen with the adoption of industrial procedure in the manufacturing of scientific instruments. As a result, the company survived into the mid 1950s while many other instrument makers were forced to close. The triple circle along with the modified lattice sextant is the most popular of sextant designs. Its open frame and strong construction ensures it is easy to handle and robust enough for everyday use.SignificanceThis vernier screw is significant in its association with a triple circle sextant, which represents the high level of technological development achieved in the design and manufacture of navigational instruments in the 19th century.