Over one hundred and thirty letters, [?1831]-[c. 1860], from Henry Petty-Fitzmaurice, third marquis of Lansdowne, to Nassau William Senior, mainly discussing parliamentary business and contemporary political issues, including Ireland and poor law administration, often with reference to Senior's own writings.

Memoranda by Nassau Senior on a conference on the Irish church and education, [c. 1835], on the redundancy of population in Ireland, 1837 (two versions) and on Poor Law administration in Ireland, [c. 1837]. The memoranda are accompanied by covering letters from Senior to Lord Howick, 1837, and to Lord Lansdowne, 1835-1837.

Twenty-eight letters, 1832-1859, from Nassau Senior to Lord Lansdowne as President of the Cabinet Council, some discussing contemporary political issues including Poor Law administration, Ireland and the economy. Others are written from Paris, Athens and various German towns and refer to the political situation and social conditions in these respective countries.
Also included are two letters, 1835-1836, from Alexis de Tocqueville to Lord Lansdowne, together with transcripts of four letters, 1848-1855, from de Tocqueville to Nassau Senior; one letter, 1848, from George Sumner to Nassau Senior discussing the 1848 revolution in France; and other related letters.