Jesse Ramsden

English designer of scientific tools

• Born: October 6, 1735
• Birthplace: Halifax, Yorkshire, England
• Died: November 5, 1800
• Place of death: Brighton, Sussex, England

Ramsden developed a new way of calibrating measurement instruments, and he applied his method most spectacularly to the construction of large optical instruments, especially astronomical telescopes, of better quality than any that had been made in England before.

Primary fields: Astronomy; mechanical engineering

Primary inventions: Dividing engine; theodolite

Early Life

Jesse Ramsden was the son of Thomas Ramsden, an innkeeper, but little else is known about his family, and information relating to his upbringing is sparse. Between the ages of nine and twelve, he attended the free school in Halifax, and he then went to live with an uncle surnamed Craven somewhere in the North Riding of Yorkshire. While he was there, he studied mathematics with a clergyman surnamed Hall before being apprenticed to a cloth-worker in Halifax.

After completing his apprenticeship in 1755, Ramsden went to London, where he was initially employed as a clerk in a cloth warehouse, but in 1756 he bound himself as an apprentice, for a fee of œ12, to Mark Burton, a mathematical instrument maker based on Denmark Street. He soon established a reputation in that occupation for the quality of his work and his assiduity, and he began trading in his own name in the Strand in 1763. He spent a great deal of time at the home of a near neighbor, John Dollond, whose family was famous as makers of optical instruments (its name was still preserved in the early years of the twenty-first century in that of the active firm of British opticians Dollond and Aitchison). On August 10, 1766, Ramsden married John Dollond’s daughter Sarah (1743-1796) at St. Martin-in-the-Fields, at the western extremity of the Strand.

As part of his bride’s dowry, Ramsden received a share in the patent rights to the achromatic lens, which John Dollond had developed and whose deployment improved astronomical telescopes markedly, although its similar impact on microscopy was delayed for nearly a century because of the difficulty of grinding the smaller lenses required by such instruments. Ramsden immediately opened his own premises as a dealer in optical instruments in the Haymarket. Sarah bore two sons and two daughters between 1767 and 1771, but only one child—John (1768-1841)—survived infancy.

Life’s Work

Ramsden’s own expertise as an inventor was mobilized by the desire to bring about improvements to the accuracy of astronomical instruments measuring angles, which were much in demand for mapping the heavens and attempting to determine stellar parallaxes—the key to measuring stellar distances. Although no stellar parallax would be measured until after his death, further pressure of demand was exerted by the Royal Navy’s desire to find a means of accurately measuring longitude. Although this quest is often represented as one for better ships’ chronometers, it also required minutely accurate sextants. It was a new method of “dividing” sextants—marking up their scales in degrees—that was Ramsden’s first triumph as an engineer. He devised a machine—a “dividing engine”—that could lay out such scales mechanically with considerably greater speed and somewhat greater accuracy than a highly skilled craftsman working by hand.

The dividing engine worked on any instrument with a circular scale, including theodolites and octants as well as sextants. The first version became operational in 1767, a second and superior one in 1775. In the meantime, Ramsden moved to larger premises in Piccadilly, although Sarah and his son did not go with him, initially remaining in the Haymarket in a house owned by the Dollonds. The two dwellings were no more than a hundred yards apart, and Ramsden seemingly continued to use his contact with the Dollonds to cultivate useful acquaintances and clients. It is impossible to determine exactly what went wrong with the marriage, but the split was permanent; Sarah was living in Lambeth when she died. A profile of Ramsden published in The Mirror of Literature, Amusement and Instruction on July 28, 1827, represented him as living in contented domesticity surrounded by his apprentices, with whom he talked shop all day and all night, but reported that he frequently hummed or sang a popular ballad whose refrain included the couplet “If she is not so true to me/ What care I to whom she be?”

Ramsden’s original dividing machine was sold to Jean Baptiste Gaspard Bochart de Saron and smuggled into France (England and France were at war at the time), where it was confiscated during the Revolution and ended up in one of the national collections. It is still on display. The second remained in England, working so successfully that the Commission of Longitude awarded Ramsden a bounty of œ300 and bought the rights to the engine for a similar sum, on condition that he provided comprehensive details of its design and construction. He was subsequently able to charge six shillings for graduating sextants for clients. His Description of an Engine for Dividing Mathematical Instruments was published in 1777.

Ramsden then turned his hand to the development of dividing engines for straight line scales, attaining an accuracy of 1/4,000 of an inch in 1779. In 1780, he expanded the Piccadilly premises considerably, giving him the space to work on large astronomical instruments, and that became his vocation thereafter, although a workforce of sixty men continued to work on smaller instruments in order to sustain his income. It was as well that they did, because he soon acquired a reputation for unpunctuality in executing major commissions, his perfectionism leaving him incapable of delivering a completed instrument until he was satisfied with its accuracy. An oft-quoted anecdote related that he once turned up at Kew Palace, mistakenly claiming to have an appointment with King George III to deliver a telescope; when the king graciously consented to see him, Ramsden allegedly pointed out that, although he had come on the right day, he had unfortunately “mistaken the year.”

Ramsden was elected a fellow of the Royal Society on January 12, 1786. He was the first telescope maker to use a fully circular scale for measurement, which could not be divided mechanically and thus posed a severe challenge to his craftsmanship; he rarely completed one in less than 150 days and often took far longer if he hit a snag that required readjustment or—on occasion—a fresh start. His first full-scale astronomical apparatus was delivered to Giuseppe Piazzi in 1789 and was installed at Palermo Observatory, where it played a part in numerous significant observations of the solar system. It is arguable, however, that a more significant instrument of Ramsden’s manufacture was a 36-inch theodolite that he designed for General William Roy’s project to reevaluate the longitude between Greenwich and Paris, which was the seed of the Ordnance Survey.

Ramsden also experimented with clockwork-driven equatorial telescopes, based on a design he had published in 1774; he remodeled one in the Royal Observatory at Greenwich in 1775, but the best instrument of that kind he built was one constructed for Sir George Shuckburgh in 1793. Following in John Dollond’s footsteps, Ramsden produced an achromatic “Ramsden eyepiece” for telescopes that was very widely used; he also produced two new micrometer designs and a wide variety of other instruments, including barometers, levels, precision balances, and pyrometers. In 1795, he received the Royal Society’s Copley Medal for “various improvements to philosophical instruments.” He corresponded with scientists throughout Europe, and he was granted membership of St. Petersburg Academy in 1794. Several of his apprentices went on to forge successful careers, including Thomas Jones (1775-1852), and his business was taken over after his death by his foreman, Matthew Berge, who continued trading in Piccadilly until his own death in 1819. Ramsden died in Brighton, but his body was brought back for burial in St. James’s Piccadilly, in close proximity to his business premises.

Impact

Although it was his large instruments that made Ramsden famous—and delays in their delivery that earned him a wry notoriety—he certainly had a greater practical impact in his own day by virtue of his accurate calibration of small instruments, especially naval sextants. The marine chronometers that “solved” the problem of calculating longitudes at sea could not have done so had they not been operated in collaboration with accurate sextants, whose rapid production Ramsden made feasible. His discovery of the dividing machine was unspectacular by comparison with such contemporary innovations as the steam engine, but the sum of its tiny contributions to millions of measurements was nevertheless vast. His large telescopes did assist considerably, though, in making numerous astronomical discoveries, and his work on equatorial telescopes was a foundation on which many subsequent instrument makers built.

Bibliography

Brooks, J. “The Circular Dividing Engine: Development in England 1739-1843.” Annals of Science 49, no. 2 (1992): 101-135. A concise but elaborate account of the historical buildup to Ramsden’s key invention and its significance as an addition to the Victorian technological repertoire.

Chapman, Allan. Dividing the Circle: The Development of Critical Angular Measurement in Astronomy, 1500-1860. 2d ed. New York: John Wiley & Sons, 1995. A comprehensive history whose later chapters include a careful analysis of Ramsden’s innovations and their impact on astronomical exploration.

‗‗‗‗‗‗‗. “Jesse Ramsden.” In The Oxford Dictionary of National Biography, edited by H. C. G. Matthew and Brian Harrison. New York: Oxford University Press, 2004. A succinct biography that offers more technical detail of Ramsden’s innovations than is usual in DNB articles.

McConnell, Anita. “From Craft Workshop to Big Business.” London Journal 19 (1994): 36-53. A brief preliminary sketch for McConnell’s comprehensive biography of Ramsden, providing a succinct and nontechnical summary of the principal details of his career.

‗‗‗‗‗‗‗. Jesse Ramsden (1735-1800): London’s Leading Scientific Instrument Maker. Burlington, Vt.: Ashgate, 2007. A definitive biography, with a great deal of technical information about the instruments he constructed and a useful analysis of the reasons for his success.