Copy letter, from Sir John Herschel to William Whewell, dated at 32 Harley St. Copy of letter, copied as part of the correspondence project led by Colonel John Herschel FRS following the death of his father. Suggests how to reconcile William Whewell's directions for tidal observation with those provided by Frederick Beechey for John Frederick William Herschel's Admiralty Manual. Thanks William Whewell for and comments on his publication on political economy. Asks William Whewell for views on decimal coinage. 2 February 1851