| Reference number | Title | Date |
| EC/1901/14 | Watson, William: certificate of election to the Royal Society | |
| MS/377/1/148 | Letter from William Watson, Royal College of Science, London, to [William Fletcher] Barrett | 27 March 1906 |
| NLB/11/545 | Copy letter from Herbert Rix, to Messrs Harrison & Sons | 19 July 1895 |
| NLB/11/544 | Copy letter from Herbert Rix, to Mr Collings | 19 July 1895 |
| NLB/11/972 | Copy letter from Herbert Rix, to Messrs Harrison & Sons | 12 November 1895 |
| RR/15/280 | Referee's report by Richard Tetley Glazebrook, on a paper 'A determination of the value of the earth's magnetic field in international units' by William Watson | July 1901 |
| RR/16/247 | Referee's report by William Watson, on a paper 'Modified apparatus for the measurement of colour and its application to the determination of the colour sensations' Sir William de Wiveleslie Abney | May 1905 |
| RR/16/388 | Referee's report by William Watson, on a paper 'An electrical measuring machine for engineering gauges & other bodies' by Dr P E Shaw | 9 January 1906 |
| NLB/23/2/128 | Copy letter from Arthur William Rucker, to William Watson, Fellow of the Royal Society | 4 November 1901 |
| NLB/23/2/129 | Copy letter from Arthur William Rucker, to William Watson, [Fellow of the Royal Society] | 4 November 1901 |
| NLB/28/613 | Copy letter from Robert William Frederick Harrison, to Dr William Watson, Fellow of the Royal Society | 18 April 1904 |
| NLB/25/328 | Copy letter from Robert William Frederick Harrison, to William Watson, Fellow of the Royal Society | 17 October 1902 |
| NLB/32/121 | Copy letter from Robert William Frederick Harrison, to Professor William Watson, Fellow of the Royal Society | 9 January 1906 |
| NLB/32/605 | Copy letter from [Archibald Geikie or Joseph Larmor], to William Watson, [Fellow of the Royal Society] | 23 April 1906 |
| NLB/47/748 | Copy letter from Robert William Frederick Harrison to Dr W [William] Watson FRS | 5 April 1913 |
| NLB/48/4 | Copy letter from Robert William Frederick Harrison, to Professor [William] Watson, Fellow of the Royal Society | 25 April 1913 |
| NLB/48/492 | Copy letter from Robert William Frederick Harrison, to Dr [William] Watson, Fellow of the Royal Society | 14 July 1913 |
| NLB/52/271 | Copy letter from Robert William Frederick Harrison, Assistant Secretary of the Royal Society; to Dr. Charles Chree, FRS | 1 November 1915 |
| RR/16/198 | Referee's report by William Watson, on a paper 'The effects of changes of temperature on the modulus of torsional rigidity of metal wires' by Frank Horton | 18 April 1904 |
| RR/22/128 | Referee's report by William Watson, on a paper 'A portable variometer for magnetic surveying' by George Walker Walker | December 1915 |
| RR/21/147 | Referee's report by William Watson, on a paper 'The ignition of gases by condenser discharge sparks' by W M Thornton | 5 July 1914 |
| NLB/56/549 | Copy letter from Robert William Frederick Harrison, Assistant Secretary of the Royal Society; to [Messrs Harrison & Sons] | 6 March 1919 |
| RR/12/381 | Referee's report by John William Strutt, Lord Rayleigh, on a paper 'On the magnetic rotation of the plane of polarization of light in liquids.—Part I. Carbon bisulphide and water' by J W Rodger and William Watson | 27 June 1895 |
| RR/12/382 | Referee's report by George Gabriel Stokes, on a paper 'On the magnetic rotation of the plane of polarization of light in liquids.—Part I. Carbon bisulphide and water' by J W Rodger and William Watson | 16 July 1895 |
| NLB/27/687 | Copy letter from Robert William Frederick Harrison, to William Watson, Fellow of the Royal Society | 13 November 1903 |
| RR/15/279 | Referee's report by William Grylls Adams, on a paper 'A determination of the value of the earth's magnetic field in international units' by William Watson | 18 July 1901 |
| RR/15/295 | Referee's report by William Watson, on a paper 'Experimental researches on drawn steel. - Part I. The influence of changes of temperature on magnetism. Part II. Resistivity, elasticity and density, and the temperature coefficients of resistivity and elasticity' by J R Ashworth | February 1902 |
| MC/19/834 | Letter from William Watson, 7 Upper Cheyne Row, Chelsea, to the Assistant Secretary of the Royal Society | 7 December 1904 |
| MC/19 | Volume 19 of miscellaneous correspondence regarding business matters, sent to the Royal Society | 1904 |