Copy of draft letter, from Sir John Herschel to Hugh Percy (3rd Duke of Northumberland), dated at Feldhausen Copy of draft letter, copied as part of the correspondence project led by Colonel John Herschel FRS following the death of his father. Describes his observational activities, especially the discovery of the variable nature of Eta Argo, and the rediscovery of the sixth satellite of Saturn. 1837-12-16/17