Correspondence of 1896-1905 concerning a proposed new comparison of theory with the Greenwich observations of the Moon from 1750. The correspondents include S. Newcomb, E.W. Turner and D. Gill.

Correspondence with S. Newcomb concerning errors in the tables of Mars, 1905.

Correspondence with S. Newcomb regarding comparisons of Sir George Airy's longitudes of the Moon with Hansen's tables, 1905.

Mr Cowell's memoranda on gravitational calculations and empirical terms of lunar longitude, 1906.

Correspondence with S. Newcomb, 1908, who requests tabular errors of the Moon.

Newspaper cutting announcing the discovery of a new planet beyond Neptune, with correspondence with J.D. Forbes, 1909.

Dr T.J.J. See's paper on the cause of the circularity of planetary orbits and the origin of the solar system, with notes by P.H. Cowell, 1909.

Correspondence with J.D. Forbes concerning errors in Neptune's orbit and a trans-Neptunian planet, 1905.

Correspondence with J. Hakes, London, concerning his new theory of lunar motion, 1906.

Letter from A. Webb enquiring about the velocity of planets in their orbits, 1907.

Letter from J.F. Phipps concerning a new theory of small planetoids, 1907.

Correspondence with G.H. Hickson concerning his discovery of errors in the 'Diurnal' method of parallax, 1907.

Correspondence with the Hydrographer of the Navy regarding gravitational calculations and the sidereal period of Mars, 1907.

Cutting from the 'Liverpool Daily Post' of a letter on irregularities in the Moon's declination, 1908.

Letter from J. Phipps, Suffolk, concerning his modification of Bode's law of the ratios of planetary distances, 1909.

Letter of acknowledgement to S. Soholoff, Pulkova Observatory, Moscow, for the results of the planetary observations, 1909.

Letter from N. Emery, London, asking various questions about lunar distance and motion, 1910.

Correspondence with W. Gorrold concerning perturbations of Uranus by Saturn, 1913.

Correspondence with Professor Porrett on Turner's sunspot theory, 1913.

Letter from the Revd Cronin concerning the sidereal period of Saturn, 1914.

Letter from Dr Phillips concerning gravitation, 1915.

Letter from C. Mason concerning the analogy of the solar system with the atomic system, 1915.

Correspondence from T.J.J. See, California, concerning his theory of lunar motion, 1916.

Correspondence with A.H. Barley concerning the theory of gravitation, 1917.

Correspondence with W.A. Cartile concerning his theories of planetary motion and gravitation, 1918.

Paper from F.A. Black, Inverness, concerning the rotation of planets, 1919, including correspondence with the Royal Society of Scotland.

Letter from W. Leighton-Jordan concerning his paper on the precession of the equinoxes, 1919.

Letter from C. Floyd Perkins concerning life on Mars and Saturn, 1920.

Correspondence with J.D. Forbes concerning observations of Neptune, 1920.

Correspondence with W.H. Pickering, U.S.A., 1920, concerning observations of Neptune from 1906-1920.