Correspondence with A.R. Hinks, Cambridge Observatory, regarding observations of Eros, 1900-1907, including correspondence on the Paris observations and the sending of the results to Cambridge.

Correspondence with A.R. Hinks concerning his tables for the computation of standard coordinates, 1907-1908.

Correspondence with M. Loewy, Paris, concerning Eros, 1900-1906, including reductions of Greenwich observations; tables of errata; and tables of the results of photographic reductions for 1900-1901.

Correspondence with H.H. Turner, Oxford, concerning Eros, 1900-1906.

Correspondence with the United States Naval Observatory, Washington, 1900, regarding a suggestion for worldwide co-operation over the observing of Eros and the Royal Observatory's rejection of this idea.

Letter to Dr Banschinger of Germany concerning minor planet observations and the computation of orbits, 1899.

Letter to Professor Brunns concerning the orbit of Eros and comparison stars, 1899.

Correspondence with Dr Mawer of Devon concerning 'new' planets between the Earth and Mars, 1899.

Correspondence with 'Daily Mail' concerning the discovery of Eros and it being at opposition in 1900, with details of position and magnitude.

Correspondence with Mr Naegamvala of Poona concerning the use of his 20-inch telescope for observations of Eros, 1900.

Correspondence with F.W. Dyson, Edinburgh, concerning the Greenwich observations of Eros, 1908.

Notes of 1908 on the opposition of Jupiter and observations of satellites during 1905-1908.

Correspondence with the United States Almanac Office concerning the supplying of the 2nd edition of the 'American Ephemeris' of 1909 and regarding phenomena of Jupiter's satellites, 1909.

Memorandum by P.H. Cowell titled 'Perturbations of Eros', 1909.

Correspondence of 1911 concerning observations of the asteroid 1911 MT, with the 'Lick Observatory Bulletin', No. 222.

Correspondence with J. Jackson, Paisley, concerning observations of positions of Jupiter VIII (Pasiphal), 1913.

Correspondence concerning Jupiter's satellites, including numbers and mean distances, 1916-1917.

Letter from D. Barford, Dunstable, concerning Saturn's satellites, 1918.

Letter from F.M. Claridge, Essex, concerning reports of a second Earth satellite, 1918.

Correspondence with F.A. Simmons concerning the satellites of Mars, 1919.

Letter from the Union Observatory, Johannesburg, on observing Jupiter's satellites, 1920.

Correspondence with various individuals concerning minor planets, 1893-1907, with the Greenwich observations for 1903.

Letter from H.H. Turner, Oxford, concerning the numbering of minor planets, 1907.

Papers sent to the 'Astronomische Nachrichten' concerning the discovery of a new asteroid, 1908.