Letter listing for 1800–1809
- Jacques Henri Bernardin de Saint-Pierre to Jean Michel Moreau, 1804
- Jacques Henri Bernardin de Saint-Pierre to Jean Michel Moreau, 1804–1805
- Jacques Henri Bernardin de Saint-Pierre to [unknown], 1804–1805
- Richard Brinsley Sheridan to Sir Robert Barclay, 8th Baronet Barclay of Pierston, 1804
- Relation d'une visite à Rousseau by Christian Felix Weisse, before 1804
- Jeremy Bentham to Pierre Étienne Louis Dumont, January 1804
- père André Morellet, abbé Morellet to Joseph Marie de Gérando, baron de Gérando, January 1804
- Hester Lynch Piozzi [formerly Mrs Thrale; née Salusbury] to Lady Margaret Williams, 1 January 1804
- Hester Lynch Piozzi [formerly Mrs Thrale; née Salusbury] to Penelope Sophia Pennington [née Weston], 5 January 1804
- Hester Lynch Piozzi [formerly Mrs Thrale; née Salusbury] to Reverend Doctor Robert Gray, bishop of Bristol, 9 January 1804
- Jacques Henri Bernardin de Saint-Pierre to Jean Antoine Gay, 13 January 1804
- David Scott to John Jervis, Earl St Vincent, 14 January 1804
- David Scott to Sir Andrew Snape Hamond, 1st baronet, 23 January 1804
- Hester Lynch Piozzi [formerly Mrs Thrale; née Salusbury] to Reverend Leonard Chappelow, 25 January 1804
- Richard Brinsley Sheridan to Charles Ward, 25 January 1804