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Jesse Ramsden FRS
FRSE Fellowship of the Royal Society of Edinburgh (FRSE) is an award granted to individuals that the Royal Society of Edinburgh, Scotland's national academy of science and Literature, letters, judged to be "eminently distinguished in their subject". ...
(6 October 1735 – 5 November 1800) was a British mathematician,
astronomical Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest include ...
and scientific instrument maker. His reputation was built on the engraving and design of dividing engines which allowed high accuracy measurements of angles and lengths in instruments. He produced instruments for astronomy that were especially well known for maritime use where they were needed for the measurement of latitudes and for his surveying instruments which were widely used for cartography and land survey both across the
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and outside. An achromatic eyepiece that he invented for telescopes and microscopes continues to be known as the Ramsden eyepiece.


Life

Ramsden was born at Salterhebble, Halifax, West Riding of Yorkshire, England the son of Thomas Ramsden, an innkeeper and his wife Abigail née Flather. Having attended the free school at Halifax from 1744 to 1747, he was sent at the age of twelve to his maternal uncle, Mr Craven, in the North Riding, and there studied mathematics under the Rev. Mr. Hall. After serving his apprenticeship as a cloth-worker in Halifax, he went to London where, in 1755, he became a clerk in a cloth warehouse. In 1758 he was apprenticed to a mathematical instrument maker and he proved so proficient that he was able to set up his own business only four years later. The quality and accuracy of his instruments established his reputation as the most able instrument maker in Europe for the next forty years until his death in 1800. Jesse Ramsden (1735–1800). In 1765, Ramsden married Sarah Dollond, daughter of John Dollond, the famous maker of high quality lenses and optical instruments. Ramsden received a share in Dollond's patent achromatic lens as dowry. Little is known of their life together but Sarah did not accompany him when he moved his workshop (and home). In 1773, Ramsden moved to 199 Piccadilly but Sarah and her son lived at Haymarket at a home belonging to her father's family. At the time of her death on 29 August 1796 she lived at Hercules Buildings, off Westminster Road, Lambeth. She was buried at St Mary's, Lambeth, on 1 September 1796. In his later years he lived above the workshop with a number of his apprentices. Ramsden the optician The Ramsdens had two sons and two daughters with only one, John, living past infancy. John later became a commander in the East India Company's navy. Ramsden's dividing engine allowed instruments to be made smaller without loss of measurement accuracy. The rights for a portable sextant designed by Ramsden and used for maritime navigation were purchased by the Board of Longitude in 1777 for £300. An additional £315 was paid to allow for its construction details to be used by other craftsmen. He also received charges for servicing of the instruments. Ramsden was of a genial disposition, but at the same time infuriated his clients with his tardiness in delivering their purchases, particularly of larger commissions. His three-year delay in providing William Roy with the theodolite for the Anglo-French Survey (1784–1790) provoked a public row within the portals of the
Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...
and in its '' Philosophical Transactions''. Many delays could be attributed to Ramsden's quest for perfection, as he continually refined his designs as the slightest shortcomings were revealed. Ramsden was elected to the Royal Society in 1786 and to the Royal Society of Edinburgh in (probably) 1798. The Copley Medal of the Royal Society was bestowed upon him in 1795 for his 'various inventions and improvements in philosophical instruments.’ Ramsden's health began to fail and he traveled to
Brighton Brighton ( ) is a seaside resort in the city status in the United Kingdom, city of Brighton and Hove, East Sussex, England, south of London. Archaeological evidence of settlement in the area dates back to the Bronze Age Britain, Bronze Age, R ...
on the south coast to try to benefit from its better climate; he died there on 5 November 1800. He was buried at St James's Church, Piccadilly on 13 November. His instrument-making business in London was taken over by his foreman, Matthew Berge until his death in 1819. The estate passed on to his son. Many of Ramsden's apprentices such as William Cary went on to establish their own instrument-making ventures. Others like Edward Troughton incorporated ideas from Ramsden into their own designs.


Ramsden's instruments


Dividing engines

Ramsden created one of the first high-quality dividing engines. This led to his speciality in dividing circles, which began to supersede the quadrants in observatories towards the end of the 18th century. He published a ''Description of an Engine for dividing Mathematical Instruments'' in 1777.


Other instruments

He also built an early plate electrostatic generator in 1768.


Surveying instruments

In about 1785, Ramsden provided General William Roy a new large theodolite which was used for the measurement of the latitude and longitude separations of London (Greenwich) and Paris and later for the Principal Triangulation of Great Britain. This work provided the basis for the subsequent
Ordnance Survey The Ordnance Survey (OS) is the national mapping agency for Great Britain. The agency's name indicates its original military purpose (see Artillery, ordnance and surveying), which was to map Scotland in the wake of the Jacobite rising of ...
of the counties of Britain.


Telescopes

Ramsden is also responsible for the achromatic eyepiece named after him. In its simplest form it consists of two planoconvex lenses with the curved sides facing each other and separated by a gap of about 2/3 of their focal length. It had the additional advantage of allowing a greater distance (or eye relief) between the lens and the eye. It thus also allowed sunshades and prisms to be placed before it. The
exit pupil In optics, the exit pupil is a virtual aperture in an optical system. Only ray (optics), rays which pass through this virtual aperture can exit the system. The exit pupil is the image of the aperture stop in the optics that follow it. In a optic ...
of an eyepiece was once called the ''Ramsden disc'' in his honour. In 1791, he completed the Shuckburgh telescope, an equatorial mounted
refracting telescope A refracting telescope (also called a refractor) is a type of optical telescope that uses a lens (optics), lens as its objective (optics), objective to form an image (also referred to a dioptrics, dioptric telescope). The refracting telescope d ...
. His most celebrated work was a 5-feet vertical circle, which was finished in 1789 and was used by Giuseppe Piazzi at the Palermo Astronomical Observatory in constructing his catalogue of stars and in the discovery of the
dwarf planet A dwarf planet is a small planetary-mass object that is in direct orbit around the Sun, massive enough to be hydrostatic equilibrium, gravitationally rounded, but insufficient to achieve clearing the neighbourhood, orbital dominance like the ...
Ceres on 1 January 1801.


Micrometers

He was the first to carry out in practice a method of reading off angles (first suggested in 1768 by the Duc de Chaulnes) by measuring the distance of the index from the nearest division line by means of a micrometer screw which moves one or two fine threads placed in the focus of a microscope.


Honours

Ramsden Rock in
Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...
is named after Jesse Ramsden.


Notes and references


Bibliography

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External links

* * {{DEFAULTSORT:Ramsden, Jesse 1735 births 1800 deaths British scientific instrument makers Optical engineers Recipients of the Copley Medal Fellows of the Royal Society of Edinburgh People from Halifax, West Yorkshire 18th-century English people Fellows of the Royal Society Honorary members of the Saint Petersburg Academy of Sciences 18th-century English engravers English inventors