Leather case for Drum sextant
Dateafter 1826
Object number00050196
NameCase
MediumLeather
DimensionsOverall: (Empty) 75 x 80 x 45 mm, 47 g
ClassificationsTools and equipment
Credit LineANMM Collection
DescriptionCompact and robust, pocket sextants such as this 19th century instrument made by Troughton and Simms are marvels of precision. The divisions on the scale are so fine that they must be read using the small magnifier incorporated into the index arm.HistoryBox or pocket sextants are small sextants entirely contained within a metal case. First developed at the end of the 18th century, they are usually all brass with most of the mechanical components inside the case. The telescope extends from an opening in the side. The index and other parts are completely protected when the case cover is slipped on. Their accuracy was enabled by improvements in the dividing engines used to graduate the arcs. The arcs are so small that magnifiers are attached to allow them to be read.
Edward Troughton (1756 - 1835) established himself as a leading instrument maker in Britain in the early 19th century. He was awarded the Royal Society's Copley Medal in 1809 and elected a Fellow of the Royal Society in the following year. In 1826, towards the end of his life, Troughton took on William Simms as a partner and the firm became known as Troughton & Simms and traded under that name from 1826 to 1922.
SignificanceManufactured by Troughton & Simms (one of the best-regarded British instrument making firms of the 19th century) this pocket sextant represents an important step in the evolution of navigation instruments. Despite its diminutive size it remained a highly accurate instrument thanks to advances in instrument tooling in the 19th century.
1810-1860
