M.S. Letter from John Barton to Matthew Boulton, 5 September 1806. (Describes Barton's Atometer, with drawing. With 2 loose papers of calculations referring to Atometer. In brown envelope inscribed:- "Original Letter Sir J.B. to Mr. Boulton describing Atometer") M.S. Letter from John Barton to Matthew Boulton 1806