Copy letter, from Sir John Herschel to John Tyndall, 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. 'Great Comet of 1843' presents difficulties for John Tyndall's explanation of comets' tails [continuation of John Frederick William Herschel's 1869-5-28]. 29 May 1869