Copy letter, from Sir John Herschel to Thomas Emerson Headlam, dated at Collingwood Copy of letter, copied as part of the correspondence project led by Colonel John Herschel FRS following the death of his father. When he was staying with Headlam he arranged to show him round a chemical works. Wonders if the sketch John Frederick William Herschel made at the time of a method for reducing chemical fumes is still extant. Would be glad to receive a copy of it, and the name of the works. 13 June 1844