Footnotes

An interesting instrument from Ramsden's later period, this is one of the smallest of his known sextants. According to Piazzi, Ramsden made sextants from 15inches radius down to 1.5 inches, but very few of the smaller sizes are known. A 5. 25 inches radius instrument employing a similar simple crossed-strut frame however is conserved in the Royal Museums of Greenwich (see Morzer Bruyns, 173 N° 150). Particularities of the present instrument are its lack of shades for the horizon mirror, the removable index shades, the absence of a handle or provision for attaching one or otherwise mounting the instrument, and the use of Peter Dollond's 1772 extended lever and rising piece for adjusting the horizon glass. The small size of the instrument and these peculiarities suggest that it may have been intended for non-marine use, but since it is currently without parallel in the corpus of Ramsden's sextants, there can only be speculation as to what this use might have been.

Jesse Ramsden FRS (1735 – 1800) was one of the leading manufacturers of scientific instruments in the latter part of the eighteenth century, apprenticed unusually late to the industry at the age of 21, to Mark Burton, mathematical instrument maker in Denmark Street, in the Strand. Ramsden had previously been apprenticed to a cloth worker, although abandoned this trade when he apprenticed himself to Burton in 1756.

Swiftly gaining a reputation, Ramsden began trading under his own name by 1763. It was at this time that he developed a life long association with the Dollond family. Ramsden was undoubtedly influenced by and learnt from John Dollond, who had famously invented and patented 'the achromatic lens'. When Ramsden married Dollond's daughter, Sarah, he subsequently acquired a profitable share in this patent. Opening a shop in Haymarket, near Little Suffolk Street, Ramsden traded under the sign of the Golden Spectacles

Ramsden was pioneering and forward thinking in his inventions, tackling his projects with the mindset of an engineer seeking exactitude through mechanical precision as opposed to pure draughtsmanship. It was this mentality that lead him to develop his first dividing engine in 1767, which meant that instruments such as sextants could be produced with accurately divided scales, cheaply and in a larger volume. At a time where astronomical research for the purposes of navigation was at the forefront of Britain's Maritime ambitions, Ramsden's advances allowed sextants to be affordable and portable.

Having moved his premises in 1773, to 199 Piccadilly, alongside St James's Church, Ramsden expanded this location in 1780, where he employed a workforce of 60 men. By 1789, it is thought that Ramsden had sold more than 1000 sextants. With associations and customers, such as Matthew Boulton of Birmingham, the Duke of Marlborough, and he supplied navigational instruments for Captain Cook's voyages in the Great Southern Oceans. Ramsden was recognised as a Felllow of the Royal Society in 1786 before being awarded the Copley medal in 1795 for his inventions.

He died in 1800, when his foreman Matthew Berge continued to trade and complete unfinished commissions until his own death in 1819. Ramsden's estate passed to his only surviving son, a commander in the East India Company's navy.

Literature:
Letter from Piazzi to Lalande 'on the instruments of Ramsden' in Jérôme de la Lande, Description d'une machine pour diviser les instruments de mathématiques par M. Ramsden...traduite... par M. de la Lande, Paris 1790.
W. F. J. Morzer Bruyns, Sextants at Greenwich..., Oxford & Greenwich 2009.

McConnell, Anita, 2007, 'Jesse Ramsden (1735 – 1800) London's Leading Scientific Instrument Maker', Hampshire, Ashgate Publishing Ltd.