by Allan Chapman
© Oxford University Press 2004 All rights reserved
Ramsden, Jesse (1735-1800), maker of scientific instruments, was born at Salterhebble, near Halifax, Yorkshire, the son of Thomas Ramsden, innkeeper, probably on 6 October 1735, though his baptism on 3 November is the earliest surviving record. Between the ages of nine and twelve he attended the free school in Halifax. He was then sent to live with his uncle, a Mr Craven, in the North Riding, where for four years he studied mathematics with the Revd Mr Hall, after which he was apprenticed to a Halifax clothworker. In 1755, having completed his apprenticeship, he went to London and found employment as a clerk in a cloth warehouse. By this time, however, his interests had clearly been drawn to scientific instrument making, for in 1756, at the mature age of twenty-one, he bound himself apprentice to Mark Burton, mathematical instrument maker, of Denmark Street, Strand, for a fee of £12.
Ramsden soon acquired such a reputation as a mathematical scale engraver that other instrument makers sought his services, and in 1763 he began trading under his own name, in the Strand. To improve his knowledge of optical instruments he spent his evenings and leisure hours in the nearby house of the Dollond family, one of the most famous and prosperous families in the profession. On 16 August 1766 he married Sarah (1743-1796), only daughter of John Dollond, FRS [see under Dollond family (per. 1750-1871)] at St Martin-in-the-Fields. Dollond had developed, and in 1758 patented, the achromatic lens, which allowed an image free of the coloured rings which hampered vision. Ramsden acquired a share in this lucrative patent as part of his bride's dowry. He took a shop in Haymarket, near Little Suffolk Street, trading under the sign of the Golden Spectacles. Two sons and two daughters were born to the Ramsdens between 1767 and 1771, but only John (1768-1841) survived infancy.
The foundation of Ramsden's reputation lay in the advances that he made in the design of astronomical instruments used for measuring exact angles in the heavens. By 1760 such instruments stood at the forefront of research in the physical sciences as astronomers across Europe, and especially in England, sought to obtain data that would enable them to refine their understanding of the moon's orbit, the solar, and (they hoped) the stellar, parallaxes, and to map the stars to an error of less than a single arc second. The application of astronomical research to navigation was of pressing importance to Britain as a maritime power. To find a ship's longitude at sea with the aid of tables of the moon's motion, newly compiled by Tobias Mayer and Nevil Maskelyne, seamen needed sextants which were small and light enough to be handy, yet accurately divided, and affordable. This demand led Ramsden to develop his first dividing engine, with its 30 inch wheel, in 1767. The dividing engine was a machine devised for the fast precision graduation of mathematical instruments with circular scales, such as octants, sextants, and theodolites; the mechanical concepts involved were similar to those embodied in an earlier and smaller engine constructed by Henry Hindley, a prominent clockmaker of York, which, according to tradition within the mathematical instrument making world, had been described to Ramsden by John Stancliffe. Ramsden's first engine did not measure up to his expectations, leading him to build a second, superior, machine which became operational about 1775. The old engine was used by Sarah and the apprentices for less accurate work before it was sold to the Frenchman Bochart de Saron and illegally exported (England being then at war with France), hidden in a piece of furniture. At the Revolution it was confiscated from de Saron, and it is now preserved in the Conservatoire des Arts et Métiers in Paris. The second machine consisted of a horizontal bell-metal wheel 45 inches in diameter, its rim incised with 2160 precision teeth. The teeth were engaged by an accurate lead-screw, which, turned by means of a treadle and cord, rotated the wheel through an exact, pre-selected angle. A sextant body was centred upon the wheel, and by alternately depressing the treadle and moving a radially sliding cutter, a semi-skilled operative could divide the 120° of a sextant scale in 30 minutes, to a far higher degree of accuracy than a master scale divider could have done by hand in as many hours. The engine could graduate sextants as small as 8 inches in radius, thus pioneering the development of precision miniaturization.
In 1777 the commissioners of longitude awarded Ramsden £300 for this invention, and bought rights in the engine for a further £315, on condition that he wrote a full description of its construction, and that they could nominate other craftsmen to be taught to make and use other engines of the same kind. Ramsden also agreed to divide sextants brought to him, at 6s. each. His Description of an Engine for Dividing Mathematical Instruments was published in 1777. The book was translated into French by Jérôme de Lalande and published in Paris in 1790. Having developed the circular dividing engine, Ramsden then applied the precision lead-screw to divide fractional parts in his straight line dividing engine, with which he could calibrate linear mathematical scales with an accuracy of one four-thousandth part of an inch. His description of this engine was published in 1779.
It seems that the Ramsdens did not enjoy a happy marriage, for in or soon after 1773, when Ramsden moved to larger premises at 199 Piccadilly, alongside St James's Church, Sarah and her son went to live in the Haymarket, probably at no. 55, a house owned by the Dollonds. She did not entirely sever her contacts with former associates. Ramsden's contacts with Matthew Boulton in Birmingham may have begun prior to their separation, for records from 1777 disclose exchange of workmen and each man supplying goods to the other; in 1786-7 Sarah Ramsden was corresponding from the Haymarket with Boulton on behalf of an official of the king of Naples who was negotiating for a steam engine from Boulton and Watt. She was living at Hercules Buildings, off Westminster Road, Lambeth, at her death on 29 August 1796, and was buried at St Mary's, Lambeth, on 1 September.
Expansion and further inventions
Ramsden further expanded his premises in 1780, taking 196 Piccadilly and the large, high wooden sheds behind these properties, previously occupied by a coach builder and reached from Piccadilly through a wide passageway under the intervening houses. Here he had both space and headroom to construct the large astronomical apparatus for which he became renowned. The sale of smaller instruments (some of which were imported from outside London) and sundries, together with repairs and resale of instruments, generated sufficient income to pay his workforce of sixty men.
The dividing engine, in both its circular and linear forms, became one of the key inventions of the industrial revolution, foreshadowing as it did the replacement of hand craftsmen by labourers operating complex precision apparatus. Before Ramsden, astronomical instrument makers had approached precision division through geometry; his instincts were essentially those of an engineer who sought exactitude not through draughtsmanship but by mechanical generation. Without Ramsden's dividing engine, sextants could not have been made in sufficient numbers, or cheaply enough, to transform navigational practice. By 1789 he had graduated more than a thousand sextants, not to mention numerous surveying instruments.
In the 1770s Ramsden began to experiment with the graduation of full circles for astronomical observatories, as an alternative to the large mural quadrants which were then in use throughout Europe. He was aware, probably from the work of the duc de Chaulnes in France in the 1760s, that a circle was thermally and mechanically more stable than a quadrant, and hence less prone to error when carrying a set of precision graduations. The circles forming part of Ramsden's own observatory apparatus were not divided on the engine, which was incapable of graduating such large arcs to the accuracy demanded by astronomers for fundamental research and star mapping; rather, he used an elaborate procedure of bisection and trisection, where each fraction was laid off and subjected to multiple checks and corrections by means of micrometer microscopes. The errors which inevitably remained on the finished circle were known and could be compensated for. In this way, Ramsden's efforts transformed the accuracy of precision astronomy from between one and two seconds of arc to half a second, a breakthrough of fundamental importance.
Ramsden's notorious slowness in completing major observatory commissions largely derived from his pioneering work on the circle. Quite simply, it was a new technology and Ramsden was a perfectionist, reluctant to finish an instrument if any suspected faults in its design were likely to rebound to his discredit once it was in the client's hands. The division of a full circle by hand took about 150 days and could only be performed in equable temperatures, and that did not take into account the resolution of any engineering problems encountered in mounting the circle and telescope for use. Ramsden's clients became exasperated with the delays, often amounting to years, between placing an order and taking delivery of an instrument, their irritation made worse by the knowledge that he was by far the best craftsman of his day. The first originally divided (that is, not engine-divided) instrument that he delivered, in 1787, was a 36 inch theodolite for General William Roy's project to remeasure the longitude between the Greenwich and Paris observatories, and out of which the Ordnance Survey developed. Two years later he had to be harassed into completing the first astronomical apparatus bearing a full circle ever constructed, of 5 feet in diameter, ordered by Giuseppe Piazzi, and installed at Palermo observatory in Sicily, where it is preserved. A mural circle 6 feet in diameter ordered for Dunsink observatory in Ireland was twenty-eight years in the making, being completed only after Ramsden's death.
Ramsden was the first instrument maker seriously to tackle the structural problems inherent in the design of equatorially mounted telescopes. In 1774 he published an account of his New Universal Equatorial and instruments of his design were constructed for George III and other prominent persons. He also built small clockwork-driven equatorials, and he remodelled the large and defective equatorial sectors which Jeremiah Sisson had built for the Royal Observatory, Greenwich, in 1775. Ramsden's truly innovative equatorial instrument was that completed for Sir George Shuckburgh in 1793. Transforming the unsuccessful equatorial sectors with which Bird and Sisson had experimented in the early 1770s, Ramsden produced a far more stable design. Using conical load bearing supports and compensating for the changing weight distribution inherent in a large 'English' equatorial mounting, he brought engineering skills to the resolution of problems of building large instruments with ponderous moving parts.
In addition to the work discussed above, Ramsden made numerous other improvements to scientific instruments. For telescopes he developed the reduced aberration 'Ramsden eyepiece', as well as two new micrometers. He made zenith sectors, barometers, levels, precision balances, and pyrometers for detecting slight changes of heat in metals, and in 1795 received the Royal Society's Copley medal for his 'various inventions and improvements to philosophical instruments'. Specimens of his craftsmanship can be found in the national collections of most countries affected by western science. Yet he was more than a superb craftsman, being acknowledged as an equal member within the international scientific community.
Reputation, character, and death
Ramsden was elected fellow of the Royal Society on 12 January 1786, and to membership of the Imperial Academy of St Petersburg in 1794. He enjoyed cordial relations with the leading scientists of the age, including such aristocratic amateurs as the duke of Marlborough, whose apparatus he had made and installed at Blenheim, and which he continued to maintain. He corresponded widely with foreign astronomers and scientists, and they called on him when in London; men from those more feudal parts of Europe were sometimes struck by the easy social acceptance of a craftsman by England's scientific gentry. Ramsden learned to read French with sufficient fluency as to enjoy Molière and Boileau, while his favourite scientific authors were Euler and Bouguer.
Ramsden's personal appearance was, according to the Revd Louis Dutens:
Ramsden died on 5 November 1800 at Brighton, where he had gone for the benefit of his health; his body was brought back for burial at St James's, Piccadilly, on 13 November. His foreman, Matthew Berge, who had been with him upwards of thirty years, completed the major unfinished instruments and continued to live and trade at 196 Piccadilly until his own death in 1819. Ramsden's estate passed to his son John, by this time a commander in the East India Company's navy. His uncles, Peter and John Dollond, were called in to make an inventory of Ramsden's assets, including his stock and machinery, which came to under £5000. Of the considerable sums owing to him, only £1300 appeared to be recoverable.
J. Aikin and others, General biography, or, Lives, critical and historical of the most eminent persons, 10 vols. (1799-1815), vol. 8
W. Pearson, An introduction to practical astronomy, 2 (1829)
E. Troughton, 'An account of a method of dividing astronomical and other instruments', PTRS, 99 (1809), 105-45
W. Pearson, 'Graduation', in A. Rees and others, The cyclopaedia, or, Universal dictionary of arts, sciences, and literature, 45 vols. (1819-20)
D. Brewster, 'Graduation', The Edinburgh encyclopaedia, ed. D. Brewster and others, 3rd edn, 18 vols. (1830), vol. 10
A. Chapman, Dividing the circle: the development of critical angular measurement in astronomy, 1500-1850, 2nd edn (1995)
A. McConnell, 'From craft workshop to big business', London Journal, 19 (1994), 36-53
J. Ramsden, Description of an engine for dividing mathematical instruments (1777)
J. Ramsden, Description of an engine for dividing straight lines on mathematical instruments (1779)
Birm. CL, Boulton and Watt collection
private information (1995)
parish register (baptisms), Halifax, Yorkshire, 3 Nov 1735
RS | Birm. CA, letters to Matthew Boulton
PRO, crown estates MSS
R. Home, oils, in or before 1791, RS [see illus.]
engraving, 1791 (after R. Home)
C. Turner, mezzotint, pubd 1801 (after H. Edridge), BM
Wealth at death
under £5000: inventory, 1800
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