Samuel Molyneux

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18 July 1689
Chester, Cheshire, England
13 April 1728
Kew, Surrey, England

Samuel Molyneux was an English astronomer who produced some new telescope designs.


Samuel Molyneux's father was William Molyneux, a notable Irish astronomer and politician, and his mother was Lucy Domville, the youngest daughter of Sir William Domville, the attorney-general for Ireland. William and Lucy had married on 19 September 1678 but Lucy had been struck down by an illness two months after the marriage and she became blind living in pain for the rest of her life. Samuel was born in Chester in England since his parents had left Dublin in January 1689 anticipating the political problems which arose in Ireland after the Roman Catholic James II, King of the United Kingdom, was deposed. The Molyneux family were Protestants and they remained in Chester until James, who had led an army in Ireland, was defeated at the Battle of the Boyne in 1690. Samuel never knew his mother for, after she returned to Dublin with him in January 1691, she only lived until May of that year.

Samuel's father, William Molyneux, began to correspond with the English philosopher John Locke beginning in 1692. Locke had written Some thought concerning education (1693) which was based on a series of letters he had written to Edward Clarke from Holland (where he had been in exile) advising him on how to bring up his son. This, of course, was now a topic of great interest to William Molyneux and he enthusiastically followed Locke's ideas in bringing up Samuel. However, William died in 1698 when Samuel was only nine years old, and from that time on he was brought up by his uncle Thomas Molyneux. When he was sixteen years old, Samuel Molyneux matriculated at Trinity College, Dublin and there he became friendly with George Berkeley who was four years his elder. Berkeley clearly had great respect for Molyneux, both as a man and as a scientist, and dedicated Miscellanea mathematica (1707) to his friend who was still an undergraduate at this time. He graduated with a B.A. in 1708 and, two years later, received his M.A. from Trinity College.

On the death of his father, Molyneux had inherited an estate at Castle Dillon in County Armagh in Ireland which brought in a good income and, after leaving Trinity College, he spent two years making improvements to the estate. In 1712 he visited England and in that year was elected to the Royal Society of London. He continued his travels going next to Antwerp where he spent the winter of 1712-13. There he met the Duke and Duchess of Marlborough who asked him to undertake a diplomatic mission to the court of Hanover. He carried out this mission and was at the court of Hanover when the Electress Sophia died on 8 June 1714 making her son Georg Ludwig, elector of Hanover, heir to the throne of the United Kingdom. Queen Anne died on 1 August 1714 and Georg Ludwig became King George I of the United Kingdom. Molyneux accompanied the new king and his family back to London where he was made secretary to George's son, the Prince of Wales. This was a position which Molyneux retained until the Prince became King George II, on the death of George I, on 11 June 1727.

The position of secretary to the Prince of Wales was only one of Molyneux's many roles. He was elected to the London Parliament, representing Bossiney and St Mawes, in 1715 then, in 1717, he married Lady Elizabeth Diana Capel, the eldest daughter of the Earl of Essex; they had no children. Before this Molyneux had a comfortable financial position, but now he was wealthy. He had always had an interest in science following in the footsteps of his father and uncle. Now he became active in astronomy and optics, particularly after he got to know James Bradley. Bradley was, like Molyneux, a fellow of the Royal Society and, after being appointed to the Savilian chair of astronomy at Oxford in 1721, moved from being an amateur astronomer to a professional one. Also in 1721, on the death of Lady Capel of Tewkesbury, a relation of Molyneux's wife, the Molyneuxs inherited Kew House. Molyneux and Bradley collaborated in innovative designs for reflecting telescopes from 1723 to 1725 and Molyneux set up an observatory at his home in Kew House. The main aim, as far as Molyneux was concerned, was to produce a design of telescope which could be made relatively cheaply and so allow a far wider range of people to become astronomical observers. He was not particularly successful in this aim for the telescopes they designed still were quite expensive to manufacture. After this the two scientists set about trying to measure the parallax of a star, the one final step which was required to prove that the earth orbited the sun and was also a necessary step in deducing a scale for the universe. Hooke had claimed to have measured the parallax of the star Gamma Draconis and their aim was to verify Hooke's result. Abrahams writes [3]:-
They purchased a George Graham zenith sector, strongly built of soldered tin plate, with a radius of twenty-four feet, an arc of 25 arc minutes, and a vernier scale that showed arc seconds. It was mounted in November 1725 at Molyneux's home on Kew Green, by boring holes through the ceiling and roof. A zenith sector swivels at the objective end, and an iron frame was attached to the chimney to mount the objective and suspend the tube. The eyepiece was 3123\large\frac{1}{2}\normalsize feet above the floor. The position of Gamma Draconis was observed over four nights between December 3 and 12, without any measurable change in position.
In fact they showed that Hooke was wrong and, having failed to measure the parallax of Gamma Draconis, they at least had shown that Hooke's value for the parallax was incorrect. In fact it would be more than 100 years later before Wilhelm Bessel made the first successful measurement of the parallax of a star.

Bradley went on to use the method developed by him and Molyneux to discover the aberration of starlight which he announced in 1728. By this time, however, Molyneux had ceased to work with him for he was on the Privy Council having been appointed as one of the lords of the Admiralty on 29 July 1727. Molyneux had been returned as a member of the London parliament in 1726 and again in 1727, and also to the Irish parliament in 1727 as representing the University of Dublin. Sadly, Molyneux had inherited the disease which had killed his mother and he was struck down by a fit while in the House of Commons in April 1728. He died a few days later. Robert Smith had been given access to Molyneux's papers and instruments a short time before Molyneux died and he took over the publication of a partially written book by Molyneux on optics. This was published as A Compleat System of Opticks (1738), and had chapters written by Molyneux on the grinding and polishing of telescope lenses and mirrors. In these chapters he explained the theories of Huygens who had visited the Royal Society in 1685, Molyneux being his host on this occasion. Huygens had kept in contact with Molyneux and had sent him his experimental results on lens before his death in 1695. Another chapter which was essentially due to Molyneux was entitled Sir Isaac Newton's Reflecting Telescope Made and Described by the Honourable Samuel Molyneux Esquire, and Presented by Him to His Majesty John V King of Portugal: with Other Kinds of Mechanisms for This and for Mr Gregory's Reflecting Telescope.

On his death Molyneux had around 700 instruments, mostly for astronomical use. Some of these had been inherited from his father William Molyneux.

References (show)

  1. Biography by A M Clerke, rev. Anita McConnell, in Dictionary of National Biography (Oxford, 2004). See THIS LINK.
  2. Biography in Encyclopaedia Britannica.
  3. P Abrahams, When an Eye is armed with a Telescope: The Dioptrics of William and Samuel Molyneux.
  4. C Molyneux, An account of the family and descendants of Sir Thomas Molyneux (1820), 32-40.
  5. R H Scott, History of the Kew Observatory, Proc. Roy. Soc. London 39 (1885), 37-86.

Additional Resources (show)

Other websites about Samuel Molyneux:

  1. Dictionary of National Biography

Cross-references (show)

Written by J J O'Connor and E F Robertson
Last Update December 2008