| RefNo | Title | Date |
| HS/13/357 | Draft letter, from Sir John Herschel to Hugh Percy (3rd Duke of Northumberland), dated at [Collingwood] | 12 October 1841 |
| HS/13/354 | Draft letter, from Sir John Herschel to Hugh Percy (3rd Duke of Northumberland), dated at Slough | 30 March 1839 |
| HS/13/353 | Letter, from Hugh Percy (3rd Duke of Northumberland) to Sir John Herschel, dated at Syon | 19 June 1838 |
| HS/13/355 | Letter, from Hugh Percy (3rd Duke of Northumberland) to Sir John Herschel, dated at Northumberland House | 9 April 1839 |
| HS/13/344 | Letter, from Hugh Percy (3rd Duke of Northumberland) to Sir John Herschel, dated at Cowes | 12 August 1833 |
| HS/13/342 | Letter, from Hugh Percy (3rd Duke of Northumberland) to Sir John Herschel, dated at Northumberland House | 10 July 1833 |
| HS/13/349 | Letter, from Hugh Percy (3rd Duke of Northumberland) to Sir John Herschel, dated at Syon | 3 September 1835 |
| HS/13/347 | Letter, from Hugh Percy (3rd Duke of Northumberland) to Sir John Herschel, dated at Alnwick Castle | 21 January 1835 |
| HS/13/350 | Letter, from Hugh Percy (3rd Duke of Northumberland) to Sir John Herschel, dated at Syon | 30 June 1836 |
| HS/13/341 | Draft letter, from Sir John Herschel to Hugh Percy (3rd Duke of Northumberland), dated at Slough | 8 July 1833 |
| HS/13/345 | Letter, from Hugh Percy (3rd Duke of Northumberland) to Sir John Herschel, dated at Buxton | 1 September 1833 |
| HS/13/346 | Letter, from Hugh Percy (3rd Duke of Northumberland) to Sir John Herschel, dated at Alnwick Castle | 28 September 1833 |
| HS/19/164 | Copy of a draft letter, from Sir John Herschel to [Hugh Percy (3rd Duke of Northumberland)] | 1840 to 1847 |
| HS/25/13/4 | Copy of draft letter, from Sir John Herschel to Hugh Percy (3rd Duke of Northumberland) | 1840? |
| HS/22/4 | Copy of draft letter, from Sir John Herschel to Hugh Percy (3rd Duke of Northumberland), dated at Slough | 30 March 1839 |
| HS/21/234 | Copy of draft letter, from Sir John Herschel to Hugh Percy (3rd Duke of Northumberland), dated at Feldhausen | 1837-12-16/17 |
| HS/22/243 | Copy letter, from Sir John Herschel to Hugh Percy (3rd Duke of Northumberland), dated at Collingwood | 12 June 1845 |
| HS/21/140 | Copy of draft letter, from Sir John Herschel to Hugh Percy (3rd Duke of Northumberland), dated at Slough | 8 July 1833 |
| HS/13/343 | Copy letter, from Sir John Herschel to Hugh Percy (3rd Duke of Northumberland), dated at Slough | 9 August 1833 |
| HS/21/145 | Copy letter, from Sir John Herschel to Hugh Percy (3rd Duke of Northumberland), dated at Slough | 9 August 1833 |
| HS/13/352 | Draft letter, from Sir John Herschel to Hugh Percy (3rd Duke of Northumberland), dated at Feldhausen | 16 December 1837 |
| HS/13/351 | Draft letter, from Sir John Herschel to Hugh Percy (3rd Duke of Northumberland), dated at Feldhausen | 25 November 1836 |
| HS/13/356 | Copy letter, from Sir John Herschel to Hugh Percy (3rd Duke of Northumberland), dated at Collingwood | 12 June 1845 |
| HS/21/214 | Copy of draft letter, from Sir John Herschel to Hugh Percy (3rd Duke of Northumberland), dated at Feldhausen | 25 November 1836 |
| HS/25/13/8 | Copy of a draft letter, from John Frederick William Herschel to Hugh Percy (3rd Duke of Northumberland), dated at [Collingwood] | 12 October 1841 |
| HS/13/348a | Copy letter, from Sir John Herschel to Hugh Percy (3rd Duke of Northumberland), dated at Cape of Good Hope | 12 June 1835 |
| HS/13/348 | Copy letter, from Sir John Herschel to Hugh Percy (3rd Duke of Northumberland), dated at Cape of Good Hope | 12 June 1835 |
| HS/21/178 | Copy letter, from Sir John Herschel to Hugh Percy (3rd Duke of Northumberland), dated at Cape of Good Hope | 12 June 1835 |