Copy letter, from Sir John Herschel to William Henry Fox Talbot, 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. Refers William Henry Fox Talbot to reference work to check William Henry Fox Talbot's experiments [see William Henry Fox Talbot's 1848-2-4]. John Frederick William Herschel says he will perform no more experiments in physical optics. 29 February 1848