| RefNo | Title | Date |
| AB/1/2/1/118 | Receipts for admissions money paid by Mr William Watson of Caius College, Cambridge and Richard Alexander Bennet | 1767 |
| AB/1/2/1/132 | Letter to James West from William Watson | 15 October 1768 |
| L&P/7/195/1 | Letter, 'Further of the comet and of a micrometer for taking angles of position' from William Herschel to William Watson | 1781 |
| L&P/7/192/1 | Letters, 'Of a comet seen on 13 March' from William Herschel to William Watson | 27 March 1781 |
| EC/1767/23 | Watson, Sir William: certificate of election to the Royal Society | |
| HS/18/113 | Letter, from Sir William Watson to Sir John Herschel, dated at Bath | 12 May 1819 |
| HS/18/118 | Letter, from Sir William Watson to Sir John Herschel, dated at Bath | 9 March 1821 |
| HS/18/117 | Letter, from Sir William Watson to Sir John Herschel, dated at Bath | 2 November 1820 |
| HS/18/110 | Letter, from Sir William Watson to Sir John Herschel, dated at Bath | 16 November 1816 |
| HS/18/114 | Letter, from Sir William Watson to Sir John Herschel, dated at Dawlish | 24 July 1819 |
| HS/18/120 | Letter, from Sir William Watson to Sir John Herschel, dated at Bath | 14 November 1821 |
| HS/18/119 | Letter, from Sir William Watson to Sir John Herschel, dated at Dawlish | 22 June 1821 |
| HS/18/111 | Letter, from Sir William Watson to Sir John Herschel, dated at Bath | 23 December 1816 |
| HS/18/109 | Letter, from Sir William Watson to Sir John Herschel, dated at Dawlish | 26 September 1816 |
| HS/18/112 | Copy letter, from Sir John Herschel to Sir William Watson, dated at Slough | 15 February 1819 |
| HS/18/115 | Letter, from Sir William Watson to Sir John Herschel, dated at Bath | 15 February 1820 |
| HS/19/38 | Incomplete copy letter, from Sir John Herschel to Sir William Watson, dated at Slough | 26 September 1822 |
| HS/18/116 | Letter, from Sir William Watson to Sir John Herschel, dated at Dawlish | 6 August 1820 |
| HS/20/183 | Copy letter, from Sir John Herschel to Sir William Watson, dated at Palermo | 16 July 1824 |