Copy letter, from Sir John Herschel to William Henry Smyth, dated at Slough Copy of letter, copied as part of the correspondence project led by Colonel John Herschel FRS following the death of his father. Discusses William Henry Smyth's observations of double stars and method of averaging positional determinations. Believes he has verified the two Uranian satellites observed by William Herschel. 6 September 1830