Letter from G.E. Hale stating his wish for a new organisation to be formed to co-ordinate solar research and to encourage work on solar problems, 1904.

Printed copy of minutes of a meeting of delegates to a conference on solar research in St Louis, 23 September 1904, with copies of 'Intensity of Solar Radiation' by Sir Arthur Schuster, 'Report on Radiation' by Vislle, 'Work with Spectroheliograph' by G.E. Hale, and 'Nene Wellenlanger-Normalen' by Kayser.

Correspondence with H.H. Turner, 1905, concerning arrangements for the conference of the Union at Oxford, 27-29 September 1905; Christie's possible attendance; and the voting on whether to have the Royal Astronomical Society Club dinner in Oxford or London.

Printed invitation to the Oxford conference signed by Sir Arthur Schuster, 1905, with a printed proof of suggestions for forming and administering the Union, the provision programme for the Oxford meeting, resolutions proposed for the 1905 meeting, resolutions on solar radiation, suggestions for discussion at the Oxford meeting, and a list of delegates and visitors.

Postcard from the Royal Astronomical Society Club signed by H.H. Turner, 1905, asking whether the dinner is to be in Oxford or London, with a card stating that the dinner is to be held in Oxford and giving times.

Cutting from 'The Times', 29 September 1905, concerning the Oxford meeting.

Letter from Sir Arthur Schuster, 1906, asking Christie to look over the proofs of the meeting minutes, with a reply.

Undated printed list of the Solar Union special committees and personnel, c. 1906.

Letter from Sir Arthur Schuster enclosing a copy of a statement by Professor A. Fowler on the work required of the Solar Union, 1906.

Invitation from P.J.C. Janssen of Paris to attend the International Congress in Paris in 1907, with a negative reply, 1906.

Correspondence and a formal invitation to attend the meeting in Paris on May 1907, with a formal reply from Christie declining the offer, 1906.

Printed letter signed by Sir Arthur Schuster asking for co-operation in observing sunspot spectra, 1906.

Letter from Sir Arthur Schuster giving details of the decisions reached at the Paris meeting with regard to observations of sunspot spectra, 1907.

Letter from W.S. Adams of Mount Wilson giving a list of times to be observed for the determination of the Sun's rotation, 1910.

Letter from Sir Arthur Schuster stating that the Carnegie Institution is providing the money for delegates to attend the meeting at Mount Wilson, 1909.

Formal invitation to attend the meeting at Mount Wilson, with a set of travelling details for conference delegates, 1910.

Correspondence with Sir Arthur Schuster, 1910, ending with Christie declining the invitation to the conference due to ill health.

Correspondence between Sir Arthur Schuster and E.W. Maunder regarding his possible attendance at the Mount Wilson meeting, 1910.

Correspondence and papers, 1911, relating to the establishment of a solar observatory in Australia, including an unsigned and undated memorandum on the solar observatory, written in the first person; an unsigned and undated memorandum, with corrections, on the establishment of this observatory; 'Statement with regard to the Movement to Establish a Solar Observatory in Australia'; newspaper cuttings on the subject of the solar observatory; and two letters from Mr Duffield of the University College, Reading, on the educational value of the Australian observatory.