(1) Correspondence regarding Commonwealth and colonial observatories, 1911-1935, including the following material:
Correspondence regarding equipment for the Mount Faber Observatory, Singapore, 1928-1930, including a transit instrument and micrometer.
Correspondence concerning the closure of the Apia Observatory, Samoa, by the New Zealand Government, 1919-1935.
Correspondence on the supply and testing of a 4-inch transit instrument and clock for the Colombo Observatory, Ceylon, 1919-1923.
Correspondence with the Colonial Office regarding the proposed establishment of an astronomical observatory in Kenya, 1929-1930.
Correspondence concerning the Hector Observatory, New Zealand, 1911-1933, including the introduction of a time signal service; instruments bought by or loaned to the observatory; Royal Observatory publications; meridian observations; and a list of members of the New Zealand Astronomical Society, 1925.
Correspondence with the Melbourne Observatory, 1915-1921, including plans of the new Magnetic House sent by the Royal Observatory and letters concerning the ordering of a travelling wire micrometer.
Correspondence with the Sydney Observatory, 1923-1931, regarding the Royal Observatory's help in obtaining a silvered glass réseau, the closure of the observatory and its progress with work for the Astrographic Catalogue.
Correspondence with the Adelaide Observatory, 1919-1920, regarding a portable transit for the observatory.
Correspondence with the Perth Observatory, 1917-1918, regarding a clock for wireless time signals, proposed changes in the control of the observatory and its closure.
(2) Correspondence with European observatories, 1896-1927, including the following material:
Correspondence with the Armagh Observatory regarding its double star work and instruments, 1924-1927.
Correspondence with the Oxford Observatory, 1915-1923, including miscellaneous correspondence with Professor Turner relating to plates, barometer records, meetings, staff salaries, etc.
Correspondence with the Bureau des Longitudes concerning a conference on fundamental stars, 1896.
Correspondence with the Tapada Observatory, Lisbon, regarding its work, 1900.
Correspondence with the Uccle Observatory, Belgium, 1906-1908, relating to lists of observatories.
Correspondence with the Milan Observatory, which sought information on observatories in the United Kingdom, 1906.
Correspondence with the Turin Observatory regarding its publication 'L'annuario astronomico', 1908.
(3) Correspondence with non-European observatories, 1894-1935, including the following material:
Correspondence with the Nizamiah Observatory, Hyderabad, India, regarding the printing of its Astrographic Catalogue, 1933.
Correspondence with the Iraqi Government concerning the proposed construction of an astronomical observatory, 1931.
Correspondence with the Observatorio Astronomico Nacional of Argentina at Cordoba, 1932-1935, regarding the printing of D.M. maps, the purchase of a Shortt clock and attacks on the director.
Correspondence with the Royal Alfred Observatory, Mauritius, 1920-1924, regarding the weather time service, new instruments and its annual reports.
Correspondence with the Turkish Embassy, London, relating to an assistant for the Constantinople Observatory, 1894.
(4) General correspondence with various observatories at home and abroad, 1928-1937, regarding meetings, conferences, new observatories, appointments, reports, expeditions and instruments.