Except for a few service papers and a letterbook, 1858 to 1870, the entire collection dates from 1865 onwards. The most important part of the collection is Hornby's official, semi-official and private correspondence, 1873 to 1894, in which many leading naval officers and other figures of the day are represented. There are also some letters written by Hornby and some correspondence of his wife and of his daughter, Mrs Egerton. Relating to Hornby's commands, there are official letterbooks for the years 1870 to 1874 and 1877 to 1880, memoranda and orders, 1865 to 1874 and 1877 to 1880, private letterbooks, 1865 to 1874, 1877 to 1878 and 1885 to 1891, and registers of telegrams received and despatched, 1877 to 1880. There are printed memoranda and papers relating to his time at the Admiralty, including the work of the Construction and Torpedo Committees.

Administrative / biographical background
Geoffrey Phipps Hornby, son of Sir Phipps Hornby (q.v.), entered the Navy in 1837 and became a lieutenant in 1844. In 1852 he was promoted to captain but remained on half-pay until 1858, after which he commanded the TRIBUNE, China, 1858 to 1860, NEPTUNE, flagship, Mediterranean, 1861 to 1862, and EDGAR, flagship, Channel, 1863 to 1865. In 1865 he was appointed Commander-in-Chief on the west coast of Africa. He was promoted to rear-admiral in 1869 and commanded the Flying Squadron in the LIVERPOOL on its voyage round the world, 1869 to 1871, and then the Channel Squadron from 1871 to 1874. Hornby was one of the Lords of the Admiralty from 1875 to 1877. He was promoted to vice-admiral in 1875. From 1877 to 1880 he was Commander-in-Chief, Mediterranean. He played an important part in the Balkan crisis of 1878, for which he was knighted and was promoted to admiral in 1879. He was President of the Royal Naval College, Greenwich, 1881 to 1882, and Commander-in-Chief, Portsmouth, 1882 to 1885. In 1885 he commanded an Evolutionary Squadron and became Admiral of the Fleet in 1888. See Mrs Frederick Egerton, 'Admiral of the Fleet Sir Geoffrey Phipps Hornby, G. C. B., a biography' (London, 1896)