Original accession (CSAC 74/4/80): The surviving material is, unfortunately, somewhat scanty. It includes a little personal and college correspondence, some notes and drafts particularly for his book Conduction of electricity through gases (first published by Thomson in 1897, third edition with his son G.P. Thomson in 1928), and various biographical accounts of Thomson and the discovery of the electron, several by his son.

First supplementary accession (NCUACS 91/4/00): The collection consists primarily of family papers and correspondence, as well as lectures, speeches, publications materials, and slight research materials. Biographical material (1874-1956) includes profiles, certificates, photographs and correspondence used by Lord Rayleigh in the preparation of his biography of Thomson THE LIFE OF SIR J. J. THOMSON O.M. SOMETIME MASTER OF TRINITY COLLEGE published in 1942. The family and personal papers (1836-1952) are extensive and consist of correspondence received by members of the Thomson and Paget families. The largest component of the family papers is correspondence and papers of Lady Thomson covering the period 1872-1950. Other family members represented by incoming correspondence are Thomson's son and daughter, his brother F. V. Thomson, and his father-in-law Sir George Paget. There are also family photographs and household accounts. The Trinity College materials (1918-1944), consists of incoming correspondence received by Thomson as Master of Trinity the bulk of which relates to college matters, students, Fellows, and meetings, but some business and personal correspondence. Correspondents include: E. Rutherford, R. T. Glazebrook, J. G. Frazer, and A. Schuster. An unexpected survival is a small number of Trinity College entrance examination papers and scripts from 1937. Research material is very slight, consisting of a few research notes and photographs for the period 1893-1934. Societies and organizations material is also slight, the most significant material being reports and minutes of the Committee on Science in the Educational System of Great Britain. Lectures, speeches, and publications material cover the period 1876-1938. There is also a notebook of typescript notes on lectures delivered at Cambridge by Thomson. Publications material includes manuscript drafts of the first edition of CONDUCTION OF ELECTRICITY THROUGH GASES (CAMBRIDGE 1903) AND RAYS OF POSITIVE ELECTRICITY (London 1913). The remaining correspondence is presented in two sequences, scientific and general. The scientific sequence includes letters from G. G. Stokes, Lord Rayleigh (4th Baron), and Lord Kelvin. The file of "Letters to JJ from distinguished people includes correspondence from Arthur Balfour, Stanley Baldwin, and Austen Chamberlain.

Second supplementary accession (NCUACS 117/3/03): These supplementary papers present significant family and personal correspondence, of which Lady Thomson is the principal recipient. It covers the period, 1882-1949, and comprises letters to Lady Thomson from various members of her family, including her twin sister, Rose and letters of thanks for hospitality at Trinity College Cambridge from visiting scientists, politicians and others. There are a few letters, 1903, from Thomson to his wife. Thomsons own correspondence is presented in two sequences: general correspondence, 1886-1939 and correspondence in French with foreign scientists 1898-1926. The general correspondence is from various scientists, politicians and academics, a large part of it being letters of thanks for hospitality at Trinity College. The correspondence in French, of both Thomson and his wife, is with a number of distinguished scientists including Marie Curie, A.H. Becquerel and Paul Langevin, principally re visits to Cambridge. There is also a little correspondence relating to Thomsons Order of Merit, press-cuttings relating to Thomson and a film of Thomson delivering a lecture in 1934.