Copy letter, from Sir John Herschel to William Stanley Jevons, 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. Is grateful for his valuable work on the Coal question. Such a work has been long wanted. Used to have a theory himself that the tides might be utilized, but working it out found it was not economic. 23 November 1865