Copy letter, from Sir John Herschel to Sir Charles Lyell, 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. Comments on the revolution of the apsides of the earth's orbit and its effect on glacier theory; further comments on the earth pyramids of Botzen [see Charles Lyell's 1865-1-31], and associated phenomena. 3 February 1865