A rare Georgian prismatic surveyor's compass, dating from c.1825. The compass is a Schmalcalder-type, with a brass case, screw-threaded lid, prism and vane sights, ring dial, transit lock, and tripod mount on the base. There are no maker's marks, but the compass lid is engraved 'J. Bennison, Liverpool' and the base of the compass is also engraved with the initials 'J B'. Jonathan Bennison (c.1793-1841) was a surveyor and map maker working in Liverpool during the early 19th century.
The compass was made sometime between c.1820-1835, definitely before 1840, as Jonathan Bennison died in 1841. There was a thriving scientific instrument trade in Liverpool at the start of the 19th century, and it seems most likely that the compass was produced by one of the makers working in the city at that time - possibly Abraham Abraham (c.1799-1863), one of the most prominent of these craftsmen. Abraham was the son of Jacob Abraham, an optician and scientific equipment supplier in Bath, Somerset. In 1817 Abraham Abraham moved to Liverpool and opened his own business at 8 Lord Street as an 'Optician & Mathematical Instrument maker'.
Certain aspects of the design of Bennison's compass are similar to the work of the London makers Charles Schmalcalder and Thomas Jones. During the early 1800's Jones was making compasses based on Schmalcalder's 1812 patent, a patent which included details of a prismatic clinometer and compass with a metal ring-type dial similar to the one seen in the Bennison compass. An example of this instrument, made c.1810-1826, and signed by 'C. A. Schmalcalder, 82 Strand, London, England', can be seen in the collection of the Science Museum in London. Schmalcalder is known to have made other instruments with metal ring dials during the early years of the 19th century, including his 'Improved Patent Portable Theodolite', consisting of a prismatic compass with a cruciform ring dial, telescopic sight, and level. This instrument, made c.1818-1826, can also be seen at the Science Museum.
The metal ring dial only came into widespread use much later in the Victorian period, when it was adopted by W. F. Stanley in the late 1850s for use in his prismatic surveying compasses and clinometers. Other makers, including Francis Barker & Son also used the ring dial for their surveying instruments in the mid to late Victorian era. The design proved to be very successful, with the Francis Barker version continuing to be manufactured until the 1980's.
The Bennison compass also has a screw-threaded lid, something that is not usually seen in the Schmalcalder-type surveying compasses. Thomas Jones is the only maker known to have produced Schmalcalder's with screw-threaded bezels in the 1820's, and it is possible that he also made examples with screw-threaded lids.
Jonathan Bennison (c.1793-1841): was a surveyor in Liverpool from the 1820's to 1841. In the 1825 edition of Gore's Liverpool Directory Bennison was listed as a surveyor with offices at 69 Castle Street, Liverpool. In the 1829 edition he was described as a 'Land Surveyor' with an office at 49 Renshaw Street. Bennison is best known for his work mapping Liverpool, producing several large scale, very high quality maps - including The Town and Port of Liverpool (1835). These highly detailed, hand-coloured maps were engraved by J. Dower of Pentonville, London, and published by Bennison. The Liverpool maps are of great historical significance, as one of the earliest accurate records of the layout of the city. One of Bennison's apprentices, George Haydock Dodgson (1811-1880), worked with George Stephenson in 1827 on the survey of the Whitby and Pickering Railway during his apprenticeship, and it seems likely that Bennison also worked with Stephenson around this time. Jonathan Bennison died in January 1841 at the age of 48, and was buried in the Parish of St. James, Toxteth.
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 of Paul Crespel at trademarklondon.com. More information on Schmalcalder, Kater and the development of the early prismatic compass can be found at the trademarklondon.com website).
Condition:
In very good condition and full working order. The compass finds North very well. The glass and prism are in very good condition, with an excellent view of the dial through the prism. The metal ring dial is in very good condition. There are general signs of wear and use and some marks to the original lacquered finish of the brass case. The fitted leather case is in good condition, with general signs of wear and some loss to the strap.
Dimensions: 75mm diameter (90mm inc. prism), height: 33mm
