Correspondence on magnetic observations, including papers on the establishment of a Magnetic Observatory in Greenwich Park and the benefits to astronomers of this research; specifications and accounts for the Observatory building; functions of the Magnetic Observatory and the provision of staff and equipment; extracts from Royal Society correspondence and minutes on magnetism and meteorology; a report on a letter by F.W.H.A.V. Humboldt concerning magnetic observations; the report of the Magnetic Committee of the British Association on the Magnetic Observatory; proposals for an international magnetic congress; lists of international magnetic observatories; a report on magnetic and meteorological observations, relating to the magnetic congress at Cambridge, 1845; correspondence on rewards to inventors of self-registering magnetic apparatus; and a synopsis of grants to scientific institutions. The correspondents include S.H. Christie, H. Lloyd, J.D. Forbes, K.F. Gauss, C. Wood, J. Barrow, F. Beaufort, T. Spring-Rice, G.C. Taylor, C. Wheatstone, R.M. O'Ferrall, W.A.B. Hamilton, C.E. Trevelyan, the Marquis of Northampton, J.W. Lubbock, E. Sabine, W. Denison, C.H.F. Peters, F. Baily, J.F.W. Herschel, T. Maclear, W.S. Stratford, R. Sheepshanks, P.M. Roget, G. Peacock, H.T.C. Corry and C. Brooke.