Copy letter, from Sir John Herschel to D[aniel] Mackintosh, 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. Agrees that a large part of the hills and valleys are due to tidal action. Comments further on this, especially relating to parts of France. The Hawkhurst lectures have ceased and are not likely to be resumed. 2 October 1866