Correspondence and papers concerning improvements and refinements to chronometers, including escapements by G.W. Linderoth, J. Gray, J.C. Bloxam, and W. Eaton; I. Hermann's escapement, with explanations and plans; C.F. Frodsham's experiments on compensator balances; E. Huntingdon's compensating pendulum; a model face of an astronomical clock; H.B. James on his invention, 'the compensator'; extracts from a report on Danish exhibits at chronometer exhibitions; correction of a clock by magnetic action; C. Frodsham on improvements in chronometer manufacture; new pendulums by R. Molyneux and W. Church; a log-watch by J.W. Tarleton; a new sidereal motor clock for the Royal Observatory; an airtight case for chronometers by J. Hammersley; L. Newin's nautical compensator; and J.C. Scotchford's lever escapement. There is considerable correspondence on J.G. Ulrich's claims for rewards as inventor of the 'double-action balance and auxiliary compensation for chronometers', with extracts from 'The Morning Herald' of 1828; a House of Commons investigation into the claim; and a copy of E.J. Dent's patent for chronometers of 1842. Other correspondents include W. Cassell, J. Barrow, G.H. Richards, J. Washington and C.P. Smyth. There are also two photographs of the workings of a watch and one of C. Frodsham's pendulums and balances.