Dear Jackson, - ..First and most unfortunately, I have been four times after Bach, and have never laid eyes on him.. ..but surely I shall catch Bach soon to get you an answer to your letter..
Source, in full
letter to his friend & composer William Jackson of Exeter, from Pall Mall, 25 Jan. 1777; as cited in Thomas Gainsborough, by William T, Whitley; New York, Charles Scribner's Sons – London, Smith, Elder & Co, Sept. 1915, p. 388