Castlereagh, Robert Stewart, Viscount, 1769-1822; Londonderry, Charles William Vane, Marquis of, 1778-1854. Memoirs and correspondence of Viscount Castlereagh, second marquess of Londonderry. 12 vols. 1848-53. :

Vol. 1 : The Irish Rebellion: https://archive.org/details/memoirscorrespon01castuoft

Other vol. downloads:

https://archive.org/search.php?query=Memoirs%20and%20correspondence%20of%20Viscount%20Castlereagh