He was born on 21 February 1788 in London, England to parents Francis Ronalds and Jane Field. Varying sources give him either ten or eleven siblings. He left school at fifteen and at nineteen his father died, leaving him and his mother to take over the family cheesemonger business. He was fascinated in practical science as a child and was encouraged by Jean Andre de Luc to explore electricity in 1814. He created an electric telegraph in 1816 and sent messages through eight miles (13 km) of wire arranged in his garden at Kelmscott House, 26 Upper Mall, Hammersmith, London (west end of London). The wire was enclosed in glass tubing and buried in trenches which ran around in the garden. Ronalds went to the British Admiralty (Navy), but they said they were not interested, so Ronalds soon gave up. He never patented his work and it fell upon Charles Wheatstone and William Fothergill Cooke to later patent and popularise the model.
Ronalds then took to travelling around Europe and the Mediterranean studying science. During this time he began collecting the Ronalds Library, now containing 2,000 volumes and 4,000 pamphlets. It was presented to the Institution of Electrical Engineers (initially Society of Telegraph Engineers) under a trust deed in 1875. In 1843 he became director and superintendent of the Kew Meteorological Observatory. His work involved a system of registering meteorological data.
He retired in 1852 and was able to live comfortably off a pension for his services to science. He continued working on various projects including his library, and record keeping. He was knighted for his contributions to the invention of the telegraph and died in Battle, Sussex on 8 August 1873.
- Ronalds' Biography at the Institution of Engineering and Technology site
- A collection of internet biographies
- His portrait at the National Portrait Gallery National Portrait Gallery (London)