Letter listing for 1780–1789
- Jacques Henri Bernardin de Saint-Pierre to Charles Eugène Gabriel de La Croix de Castries, marquis de Castries, April 1780
- Gustavus III, king of Sweden to Evert Vilhelm Taube, Baron Taube, 1 April 1780
- Gustavus III, king of Sweden to Greve Gustaf Filip Creutz, 1 April 1780
- René Louis de Girardin, marquis de Girardin to François Coindet, 4 April 1780
- père André Morellet, abbé Morellet to William Petty, 1st marquess of Lansdowne [2nd earl of Shelburne], 4 April 1780
- père André Morellet, abbé Morellet to William Petty, 1st marquess of Lansdowne [2nd earl of Shelburne], 4 April 1780
- Marie Anne de Vichy-Chamrond, marquise Du Deffand [née de Vichy] to Horace Walpole, 4th earl of Orford, 4 April 1780
- William Cowper to Reverend William Unwin, 6 April 1780
- père André Morellet, abbé Morellet to Frédéric Samuel Osterwald and Abraham Bosset de Luze, 7 April 1780
- Charles Eugène Gabriel de La Croix de Castries, marquis de Castries to Jacques Henri Bernardin de Saint-Pierre, 8 April 1780
- William Cowper to John Newton, 9 April 1780
- père André Morellet, abbé Morellet to Frédéric Samuel Osterwald and Abraham Bosset de Luze, 9 April 1780
- Jeremy Bentham to Sir Samuel Bentham, 10 April 1780
- Pierre Alexandre Du Peyrou to Paul Claude Moultou, 10 April 1780
- Jeremy Bentham to Sir Samuel Bentham, 11 April 1780