Copy letter, from Sir John Herschel to Dionysius Lardner, dated at 12 Charlotte St. Copy of letter, copied as part of the correspondence project led by Colonel John Herschel FRS following the death of his father. Accepts arrangement proposed by Dionysius Lardner. John Frederick William Herschel will write a volume on astronomy [Treatise Astr.], but will need time. 14852 28 February 1829