Joseph John Thomson, the Master of Trinity College between 1918 and 1940, was a Nobel Laureate in Physics who first distinguished himself as Professor of Experimental Physics at the Cavendish Laboratory.
Thomson was born on 18 December 1856 in Cheetham Hill, Manchester. His father, Joseph James, ran an antiquarian bookshop that had been in the family for several generations, and his mother Emma came from a local textile family. Thomson showed an early aptitude and enthusiasm for science, and was only 14 when he enrolled at Owens College, Manchester to study engineering, mathematics, physics and chemistry. He later joked that “the authorities at Owens College thought my admission such a scandal … that they passed regulations raising the minimum age for admission, so that such a catastrophe would not happen again.” After graduating in 1876, Thomson won a scholarship to study for the Mathematical Tripos at Trinity College, Cambridge, where he later became a Fellow in 1880.
In 1884 Thomson was appointed to the prestigious post of Professor of Experimental Physics at the Cavendish Laboratory, a position which he held for 34 years. The laboratory’s reputation for scientific discovery and innovation flourished during Thomson’s tenure, in large part due to his personal efforts to incorporate the visiting scholarship postgraduate research students into the wider community of Cambridge scientists. Thomson was a gifted teacher and mentor; nine of his students and research assistants would later win Nobel Prizes in Physics or Chemistry – including Niels Bohr, whose Bohr model of the atom is still used to introduce students to quantum mechanics, and Ernest Rutherford, whose research into radioactive substances laid the foundation for modern nuclear physics.
One of Thomson’s greatest achievements came during his research on cathode rays, particularly observing cathode rays as they travelled through air and reacted to electric and magnetic fields. Thomson theorised that cathode rays were streams of negatively charged subatomic particles, which were around 1/1000 of the mass of a hydrogen atom and had an extremely high charge-to-mass ratio. On 30 April 1897 he gave a lecture at the Royal Institution and announced his discovery of particles called ‘corpuscules’, which were later known as ‘electrons’. In 1906, Thomson was awarded the Nobel Prize in Physics for his research into the conduction of electricity in gases.
Thomson became the Master of Trinity College in 1918. His status as a world-renowned physicist meant that many of his peers saw his appointment as a recognition of the importance of science itself. In this letter, the chemist Frederick Dootson congratulates Thomson and states that “when a scientist becomes Master of Trinity it does indeed look as though science were at last to come into her own!”
Thomson resigned from his position at the Cavendish Laboratory but expressed a desire to “retain my connection with the Laboratory and have charge of the Research Work.” (JJT C/8/31) His wish was fulfilled when the university appointed him as an honorary professor. As Master, Thomson remained connected to the scientific community, serving as President of the Royal Society until 1920 and giving lectures at many universities and institutions.
During his time as Master, Thomson was well-liked by Fellows and students and became involved in all areas of College life. He was particularly known for his enthusiasm for College sports, and often came to watch matches and training sessions. He was a regular guest at Trinity First and Third Boat Club events, and chaired the centenary dinner in 1925. (JJT C/58/26) One letter from the archive suggests that his keen interest in rowing was common knowledge – the writer asks for Thomson’s advice about placing a “rather heavy bet” on the Cambridge team for the 1930 Boat Race, after hearing conflicting accounts about the team’s chances in the newspapers. Thomson’s response is lost to history, but Cambridge won for the seventh year in a row, continuing a winning streak that would last until 1937 – the longest in the Boat Race’s history. (JJT C/68/2)
Thomson was Master of Trinity College for 22 years until his death in August 1940. His good friend George Trevelyan, who succeeded him as Master, described him in a letter to his brother Robert as “a frank, kindly man” and “very much … a scholar, besides being a man of science of the very highest rank”. (TRER/12/287) His extensive contributions to science are recognised in three awards: the Institute of Physics Joseph Thomson Medal and Prize, for research in atomic or molecular physics; the Institute of Engineering and Technology’s J J Thomson Medal for Electronics; and the Thomson Medal Award which is sponsored by the International Mass Spectrometry Foundation.
Thomson’s legacy is also visible around the city of Cambridge. J J Thomson Avenue on the university’s West Cambridge site is named after him, and the science laboratories at the Leys School have been housed in the Thomson building since 1927. There is a plaque commemorating his discovery of the electron outside the old Cavendish Laboratory on Free School Lane, and his bust can be found on the staircase leading up to the Wren Library.
The majority of Thomson’s papers are kept in the archives at Trinity College.
 Recollections and reflections p. 2.