General and scientific correspondence (ca. 4500 letters), the 850 correspondents including John Tyndall, Sir Joseph Hooker, Michael Foster, Charles Darwin, Sir Charles Lyell, Alexander Agassiz, Rev. Benjamin Jowett and Herbert Spencer (arranged in alphabetical order); nearly all the letters exchanged between T.H. Huxley and his wife from 1847-1895; letters written to Mrs Huxley and to his son, Dr Leonard Huxley; notes, drawings and photographs used in the preparation of scientific papers and lectures; diaries and sketchbooks kept on the voyage of Rattlesnake; manuscripts of a number of his books and contributions to journals; engagement diaries; newspaper cuttings and other printed material.