Copy of a draft letter, from John Frederick William Herschel to David Brewster Copy of draft letter, copied as part of the correspondence project led by Colonel John Herschel FRS following the death of his father. Sends an abstract of his paper on observations relating to the practical construction of telescopes [John Frederick William Herschel's 'Practical Rules,' 1822]. Would like 25 copies for distribution. His recent experiments with polarized light. 1823