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William Cary Schmalcalder Prismatic Compass c.1815

Price $823.00 Sale

A rare Georgian survey or artillery compass, made in London by William Cary c.1815. The compass card is signed ‘Cary, London'. The compass was made to the specifications and design of the earliest prismatic compass, as patented by Charles Augustus Schmalcalder in 1812. An identical compass, made by Cary for Schmalcalder, and retailed from Schmalcalder's shop at 82 The Strand, London, can be seen on p.40 of Kornelia Takacs' book Compass Chronicles (Schiffer, 2010).

The compass has an ornately designed green compass card, with cardinal and intercardinal markers, and a reversed azimuth circle marked to 360 degrees, divided into 10 degree increments. The compass also features a lacquered brass case and lid, prism and vane sights, transit lock, and manual brake. Complete with the original fitted leather case.

William Cary (1759–1825): was an English scientific instrument maker. Cary learned the skills for producing instruments as an apprentice of Jesse Ramsden (1735-1800). He produced numerous scientific instruments including mechanical calculators, measuring instruments, telescopes, microscopes, navigation and survey equipment. William Cary had three brothers, the eldest George (c.1753-1830) was a haberdasher, while the second brother, John, was a mapmaker who also worked with William, and the last, Francis (c.1756-1836), was an engraver. After William's death in 1825, the firm was taken over by Charles Gould, who may have trained briefly under William. The company continued trading for almost 100 years, being run by various members of the Gould family, including Charlotte Hyde Gould (c.1797-1865). After 1865 the company was taken over by Henry Porter, and after his death in 1902 the business was continued by his sons until the 1920s.

Charles Augustus Schmalcalder (1781-1843) was one of the most significant figures in the development of the compass. His patent design of 1812, which introduced the idea of using an optical prism, combined with a sighting vane, to improve accuracy when taking bearings, is still in use today. Schmalcalder's innovation was a development of the work of Henry Kater. In 1811 Kater developed a design using a mirror and sighting vane. His design was then manufactured by Thomas Jones. Schmalcalder, who also knew Thomas Jones, is believed to have seen Kater's new compass at Jones' premises, and this gave him the idea for his own prismatic version. Schmalcalder moved swiftly to have prototypes of his own design made by Jones, which he then went on to patent. Winning the race to patent his innovation, Schmalcalder's compass completely eclipsed Kater's earlier design. Between 1812 and 1826 (when the patent expired) Schmalcalder's Patent compasses were manufactured by third party makers, like Thomas Jones and William Cary, and sold from Schmalcalder's premises, at 82 The Strand unti 1826, and then from 399 The Strand, London. Schmalcalder continued in business until around 1840, with his design being used uncredited by many other makers, such as Simms, Barker, Jones, and Troughton after the patent expired in 1826. No doubt as a result of this, Schmalcalder fell on hard times, dying in poverty in 1843 and being buried in the Strand Union Workhouse cemetery.


In very good condition, and full working order. The compass finds North very well. The brass case, glass, sighting vane, and prism are all in very good condition. There are some minor marks to the compass card at NNW. Both the manual brake and transit lock are working well. There is some wear to the original lacquered finish of the brass case. The original leather case is in very good condition

Dimensions: 75mm diameter (90mm inc. prism)