# Dictionary of National Biography, 1885-1900/Williams, Zachariah

​WILLIAMS, ZACHARIAH (1673?–1755), medical practitioner and inventor, was born and lived for some time at Rhosmarket, or Rosemarket, about five miles north-west from Haverfordwest, Pembrokeshire. He was educated in medicine and practised in South Wales as a physician and surgeon. While there he was on very friendly terms with the family of Philipps of Picton Castle. One of his projects in Wales was to work under a lease for twenty-one years the coal in the parish of Llangunnor, Carmarthenshire, but the scheme came to nothing. As early as 1721 he had persuaded himself that he had discovered the means of ascertaining 'the longitude by magnetism, and that the variations of the needle were equal at equal distances east and west,' and with the expectation of making his fortune by the discovery he came to London a few years later.
His earliest friend in London was 'Rowley, the memorable constructor of the Orrery' (Attempt to ascertain the Longitude, 1755). He conferred with Whiston, and submitted his scheme to the admiralty, who desired to refer it to Sir Isaac Newton. The offer was declined by Newton on account of his age, and it then went to Samuel Molyneux [q. v.], who is accused by Williams of having stolen his plan. He was next introduced to Desaguliers and others.
On the failure of these hopes of pecuniary advantage Williams was admitted on 29 Sept. 1729 as 'a poor brother pensioner' in the Charterhouse, on the nomination of Sir Robert Walpole. From December 1745 he was bedridden, without a nurse, and with no help save from his daughter, Anna Williams [q. v.] In December 1746, and later, he addressed memorials to the governors complaining of the officials, against whom his grievances were of old standing, and not altogether without foundation. The order for his expulsion was given on 19 May 1748, one of his offences being that, contrary to rules, his daughter had lived with him in the Charterhouse for two years. Stephen Gray [q. v.], also a member of the Charterhouse, 'shared all his studies and amusements,' and used to repay communications on magnetism by discoveries in electricity (ib.) William Jones of Nayland, when a schoolboy there, was a great friend of Williams (Hist. MSS. Comm. 14th Rep. iv. 540). Down to 1751 Williams continued to importune the admiralty with his scheme. It was then sent for the consideration of Bradley, the professor of astronomy, who gave it as his opinion that the 'instrument in its present state' could not be relied upon at sea. After an illness of eight months Williams died in London on 12 July 1755.
Williams was the author of: 1. 'The Mariners Compass Compleated,' in two parts; describing the variations of the magnetic needle at places whose true latitude or longitude is certainly known, 1745. Part i. had been previously issued, with a different title-page, as by Z. W. in 1740. 2. 'A True Narrative of certain Circumstances relating to Zachariah Williams in the Charterhouse,' 1749. 3. 'Account of an Attempt to ascertain the Longitude at Sea by an exact Theory of the Variation of the Magnetical Needle. With a table of Variations at the most remarkable Cities in Europe,' English and Italian, 1755. It was edited by Johnson, and the Italian translation is believed to be by Baretti. Williams invented a machine for extracting the salt​ness from sea-water and making it drinkable, which is said to have belonged to the Royal Society with his ‘sphere of iron on which a small compass moved in various directions.’
Several letters to and from him, some of his ‘corrected and others written by Dr. Samuel Johnson,’ with anecdotes by M. Green, are in the ‘Gentleman's Magazine’ (1787, ii. 757–9, 1041–2, 1157–9). The letters belonged to John Nichols.
W. P. C.