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The John Thompson Collection

Spring, 1999

IN 1932 the Museum acquired a set of instruments which the then Curator, R. T. Gunther, christened the John Thompson Collection. The collection originally belonged to an eighteenth-century gentleman from Witherley Bridge in Leicestershire named John Thompson (1720-83). Of the twenty-three instruments, the majority were made for land surveying while the remainder related to his studies in mathematics and natural philosophy. Together with some accompanying manuscript notebooks and letters, they are an important witness to the interests of a family of mathematical practitioners and philomaths in the eighteenth century.

It is not known how Gunther first came into contact with the Thompson family heirs, but by October 1932 he had evidently viewed the collection and hoped to acquire it, for he was empowered to pay up to £15 ‘on the acquisition of an ancient set of Surveying Instruments.’ However, this was insufficient to meet the price asked by the family, so Gunther arranged an outside appraisal. Both parties agreed to a price of £25 and the funds were provided by the Friends of the Old Ashmolean.

Almost immediately, a brief news article on John Thompson and the instruments appeared in Nature. Within a year, Gunther had submitted a draft paper on ‘The Plane Table and Other Instruments of John Thompson of Witherby [sic]’ to the Royal Geographical Society, obviously with a certain level of excitement.
Although Gunther viewed the instruments as a coherent group – to the extent of writing or engraving ‘John Thompson Collection’ on a number of them – the collection has over time become split up. The separation process began at accession, when the instruments were recorded in the Museum’s annual report not as a single group but mixed with other acquisitions under subject headings.

In the recent past, only the most attentive visitor will have spotted any traces of the collection, since the five instruments on display were dispersed through four different cases in the top gallery. However, last year, as part of a dissertation for the Museum M. Sc., the collection’s history and acquisition were investigated, along with the life and work of John Thompson and his family. The collection has now been reconstituted and its original use and context freshly illuminated.

John Thompson falls nicely within eighteenth-century notions of the philomath. During the period 1742 to 1767 he contributed many queries and answers to popular magazines such as the Gentleman’s Diary and Martin’s Magazine. Editors praised Thompson’s work in land surveying, geometry and fluxions, and he was described as a ‘curious and careful computer, who always commanded our esteem’.
Thompson’s most famous moment came in the mid-1760s when he undertook to re-survey the enclosed common fields of the town of Atherstone. He uncovered an error of three acres, castigating the previous land surveyors as ‘unmathematical bunglers’, and transforming his practical intervention into a prize question submitted to the Gentleman’s Diary.

Thompson’s combination of mathematical knowledge and skill in land surveying is also visible in the notebooks that accompany his instruments. One notebook belonged to Thompson himself and contains 270 pages of detailed problems and exercises on mathematical subjects, including fluxions, conic sections and geometry. A typically intricate problem involves the sun, earth and moon, and seeks ‘the Nature and Description of the curve generated by the centre of the Moon’.

This notebook shows Thompson’s own interest in contemporary mathematics. The other two volumes were written by his sons Ralph (1759-1839) and Samuel (1763-1831). Each of the manuscripts was compiled while its author was still in his teens and contains problems and exercises on land surveying.

Several surviving maps dating from 1803 to 1812 indicate that Ralph Thompson worked as a land surveyor near his Witherley home and, when coupled with statements from his last will and testament, strongly suggest that he had inherited his father’s instruments. No maps belonging to John or Samuel have been located, thus leaving Ralph as the real land surveyor of the Thompson family.

The instruments themselves include two telescopes, a plane table and drawing board, a pair of levels, a surveyor’s cross, a pantograph, a set of Napier’s bones and two Gunter chains, as well as sectors, scale rulers, slide rules, a parallel ruler and compasses. Most impressive is the plane table by George Adams senior (illustrated above), described by Gunther as ‘the most perfectly designed and executed plane-table which we have seen.’

Built of mahogany and measuring 183/4 inches square, this plane table is said to be made to John Thompson’s own design. Graduated brass scales are inset along the four outside surface edges in addition to a pair of narrow brass rules which hold down drawing paper flush to the surface. In addition, the magnetic compass box (pictured above detached) can be fixed under any of the four sides, while a sturdy adjustable brass support arm allows the table to be inclined. A heavy tripod stand also survives on which to mount the table.

The plane table is undated, but is inscribed: ‘Made by G* ADAMS in Fleet Street London, Inst: Mak:r to his Royal Highness the Prince of Wales.’ According to John Millburn, Adams senior held his appointment as mathematical instrument maker to the Prince of Wales from 1757 to 1760, a period which matches John Thompson’s activities well. A similar inscription by Adams also appears on the pantograph.

However, Thompson must have acquired some of his instruments second-hand, since the drainage level (also illustrated above) is signed and dated ‘Made by Tho Wright Instrument maker to his Royal Highness the PRINCE 1724’, when Thompson was only three or four years old.

All in all, the Thompson Collection poses a range of questions about instruments, mathematics, and land surveying and suggests a rich set of connections between the family, their instruments and maps, and even the Museum itself.

Dana Freiburger