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Longitude Essays

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Jeremiah Sisson

Jeremiah Sisson, born in 1720, was one of the most respected mathematical instrument makers in eighteenth-century England and Europe. He followed in the footsteps of his equally esteemed father, Jonathan, by taking over the family shop in the Beaufort Buildings near the Strand in London in 1747. The younger Sisson was given impressive commissions as well, including for large observatory instruments. However, he had poor business sense and went bankrupt twice, in 1751 and 1775. He was also imprisoned a number of times for not paying his employees' salaries and had to pawn some of his instruments. (It was not terribly unusual for a trade member in early modern London to go bankrupt. However, it was unusual for the well-trained son of such a famous and well-established instrument maker to do so, and twice!) Sisson obtained the well-paying position of mathematical instrument supplier to the Board of Ordnance in 1772 but then lost it when he went bankrupt three years later. He died in 1783.

Sisson was involved with longitude actors a number of times. He sold sectors and other instruments to the important Commissioner of Longitude and Astronomer Royal Nevil Maskelyne for Greenwich Observatory. (The astronomer also tried to assist the instrument maker financially at different times, and by vouching for him during commercial dealings.) In the late 1750s, Sisson constructed the marine chair of the Irishman Christopher Irwin as well. Many British and foreign visitors viewed it at the instrument maker's shop. Into the early 1760s, Irwin's chair attracted much public attention and an (unsuccessful) Board of Longitude sea trial. Sisson asked the Board for a reward in 1767 after John Bird had sought the same for his method of dividing the scales on instruments. Jeremiah argued (rather logically) that since he and Bird had both learned their dividing skills from Jonathan Sisson, that he should be rewarded as well. However, the Commissioners told him [RGO 14/5:150] 'that (supposing what he has asserted be a fact which they cannot thoroughly judge of) the Board do not think themselves authorized to give him any reward, having already given one to Mr Bird the first proposer'. This is the only time that Jeremiah Sisson appears in the surviving minutes of communal meetings of the Commissioners and may be one of the few times he appears in any of the digitised volumes.

However, there are diverse records related to the instrument maker scattered across the collections at other institutions - such as in the letters and commercial records of customers and correspondents including Nevil Maskelyne. There are also surviving instruments around the world. These include at Greenwich Observatory a piece [RMG icon] of the two 5-foot equatorial sectors which Sisson made in 1755, and a gunner's quadrant [RMG icon] from circa 1770. There is also a depiction of one of the whole sectors in a drawing by John Charnock [RMG icon] . Finally, Alex Werner of the Museum of London has identified a depiction of the Sisson shop, on the left side of this Sandby painting [link] at the British Museum - with a man depicted using the family's rooftop observatory!

Alexi Baker
History and Philosophy of Science
University of Cambridge