Correspondence, computations and records of observations in regard to the correction of compasses on the iron ship 'Rainbow'. The correspondents include F. Baily, W.H. Barlow, W.H.M. Christie, W.T. Denison, G. Dollond, R. Fitzroy and W. Whewell. The papers include plans of the basin in Deptford Dockyard; 'graphical calculations of perturbations from assumed disturbing face of permanent magnets'; and observations of the dipping needle within and exterior to the ship.