Correspondence and related papers concerning the correction of compasses on iron ships. There are papers regarding investigations of compass deviation on the 'Trident'; the work and findings of the Liverpool Compass Committee; changes in the deviation of iron ships' compasses; 'Notes on the arrangements and practice of adjusting the compasses of iron ships at Liverpool'; Dr W. Scoresby's account of the voyage of the 'Royal Charter'; compasses of the 'Great Eastern', with ratings of the standard and mast compasses; deviation of the compasses of iron ships in the 'Mercantile Magazine'; J. Gray's patent binnacle and floating compass; an anonymous paper titled 'On the changes in the deviation of ship's compasses'; and J.T. Towson's new type of compass. The correspondents include J. Washington, W.G. Romaine, F.J.O. Evans, R. Fitzroy, W. Whewell, T. Maclear, G. Fisher, the Earl of Rosse and J.T. Towson.