Corrections to compasses on iron ships, with related correspondence. The ships include the 'Nemesis', 'Vulca', 'Brigand', 'Iron Duke', 'Great Britain', 'Royal George', 'Orwell', 'Royal Sovereign' and 'Duchess of Lancaster'. The papers include instructions by Airy on correcting the compasses on iron ships and the procedure involved; deck plans of vessels, including HMSV 'Soudan'; a lecture to the Liverpool Philosophical Society on righting compasses; and specifications of vessels, including the 'Royal George'. The correspondents include F. Beaufort, W. Allen and T. Barclay.