A very rare Schmalcalder's Patent type prismatic compass, made in London by Thomas Jones c.1815. The compass card is signed 'Thomas Jones, 62 Charing Cross, London'. With a hand-drawn green compass card, lacquered brass case, prism and vane sights, and transit lock. The compass still has its original glass - a remarkable survival after more than 200 years. The compass also features a very finely made screw-threaded bezel, something which may be unique to Thomas Jones compasses. This arrangement allows the glass and bezel to be easily removed, and is not seen on other Schmalcalder-type compasses. This compass would not have had a lid, unlike those made prior to 1826 and marked 'Schmalcalder's Patent' which always had a lid. Schmalcalder's 1812 patent application includes a lid as part of the design. The compass comes complete with its original fitted leather case.
Thomas Jones (1775-1852): Thomas Jones F.R.S., F.R.A.S. was one of the most celebrated makers of scientific instruments of the 19th century. From 1789-1796 he was apprenticed to Jesse Ramsden of Piccadilly, the most eminent scientific instrument maker of the day. Jones continued to assist Ramsden until the latter's death in 1800. With his brother, Thomas Jones worked for private customers and for the trade, in particular for Charles Schmalcalder, working on Schmalcalder's Patent prismatic compass, and also for Edward Troughton of Fleet Street. By 1806 Jones had opened his first shop in Mount Street, off Berkeley Square, in 1811 he moved to 21 Oxenden Street, and in 1816 He moved to 62 Charing Cross. Major national observatories at home and overseas ordered their principal astronomical instruments from him including the Cape of Good Hope Observatory,Greenwich Observatory, Armagh Observatory and the universities of Oxford and Cambridge. In 1824 Thomas Jones of Charing Cross was appointed Mathematical Instrument Maker to the Board of Longitude, and also became a member of the Institution of Civil Engineers. Jones was one of the founder members of the Astronomical Society, and in 1835 he was elected as a Fellow of the Royal Society. Jones devised an all-metal travelling barometer and a transit instrument for Sir Henry Englefield, a lactometer for Sir Joseph Banks, and a small azimuth compass for Henry Kater. In 1850 He moved the business to 4 Rupert Street. Thomas Jones died in 1852 in his shop, and was buried at St James's Church, Piccadilly.
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 sold from Schmalcalder's premises, first at 82 The Strand, London, and later 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.
(Much of the above information on the Schmalcalder compass is based on the extensive research and expert knowledge of Paul Crespel at trademarklondon.com, who has always been very generous with his helpful and invaluable advice. For more information on Schmalcalder, Kater and the development of the early prismatic compass, go to the excellent trademarklondon.com website).
In good, original condition, and working order. The compass finds North well, although sometimes the card moves a little slowly. The original glass and prism are in very good condition, with an excellent view of the card through the prism. The sighting vane has a few dings. There are some marks to the compass card, and some wear to the original lacquered finish of the brass case. The fitted leather case is in good condition.
Dimensions: 70mm diameter (90mm inc. prism), (Leather case: 100mm x 30mm)