John Ambrose Fleming

Lore & Background

Fleming was born in Lancaster, the eldest of seven children of a Congregational minister. After early tutoring by his mother, he studied at University College School and later at University College London under Augustus De Morgan, Alexander Williamson, and George Carey Foster. Financial difficulties forced him to suspend his studies in 1868; he worked briefly at a shipbuilders drawing office in Dublin and then at a stockbroker's office before graduating with a B.Sc. in 1870. He taught science at Rossall School and Cheltenham College, then studied at St John's College, Cambridge, where he attended the final lectures of James Clerk Maxwell. He obtained a D.Sc. from the University of London in 1879 and graduated with First Class Honours from Cambridge in 1880, becoming a Fellow in 1883.

Fleming served as a demonstrator at Cambridge and briefly as the first Professor of Physics and Mathematics at University College Nottingham. In 1882 he became an electrician at the Edison Electric Light Company, advising on lighting and Ferranti alternating current systems. In 1885 he became head of the new Department of Electrical Technology at University College London, where the only equipment initially provided was a blackboard and chalk. In 1897 the Pender Memorial Committee donated £5,000 to found the Pender Laboratory and the Pender Chair, which Fleming took up. He retired in 1926 but remained active, serving as the second President of the Television Society.

Fleming was born with congenital hearing loss and attended meetings with an assistant who made notes. He was a noted photographer, painted watercolours, and enjoyed climbing the Alps. He was a Christian creationist who argued against evolution, serving as President of the Victoria Institute from 1927 to 1942, and in 1932 helped establish the Evolution Protest Movement with Douglas Dewar and Bernard Acworth. He bequeathed much of his estate to Christian charities.

Reader's Guide

Fleming's most significant contribution was the invention of the vacuum tube—the two-electrode diode, which he called the 'oscillation valve' and patented on 16 November 1904. This invention is often considered the beginning of electronics. His Fleming valve was used in radio receivers and radar for many decades until superseded by solid-state technology more than 50 years later.

In 1899, Guglielmo Marconi contracted Fleming to design a radio transmitter for the first transatlantic attempt. Fleming designed the world's first large radio transmitter, a complicated spark transmitter powered by a 25 kW alternator driven by a combustion engine, built at Poldhu, Cornwall. It transmitted the first radio transmission across the Atlantic on 12 December 1901. However, Fleming had agreed that the main credit would go to Marconi, and Marconi only credited Fleming along with several other employees, saying he did some work on the 'power plant'. Marconi also forgot a promise to give Fleming 500 shares of Marconi stock; Fleming was bitter about this treatment but honoured his agreement until after Marconi's death in 1937.

In 1906, Lee De Forest added a control grid to Fleming's valve to create the Audion, an amplifying vacuum tube RF detector. Fleming accused De Forest of infringing his patents. The court battle lasted many years with victories at different stages for both sides. The Supreme Court of the United States later invalidated Fleming's patent because of an improper disclaimer and because the technology was known art when filed. Fleming's contributions to electronic communications and radar were of vital importance in winning World War II.

Did You Know?

• Fleming established the right-hand rule used in physics.
• Fleming was born with congenital hearing loss and used an assistant to take notes at meetings.
• In 1941, the London Power Company named a coastal collier SS Ambrose Fleming in his honour.