This 18-page pamphlet contains testimony given by Edison between November 1885 and February 1886 and by Charles Batchelor and John F. Ott in August 1888 in a patent interference involving Edison and John Toby Sprague. A technical drawing by Edison also appears in the printed record as an exhibit. Included in the testimony are discussions of Edison's work on electric meters in 1878.

Related interference records can be found in Records of the Patent and Trademark Office (Record Group 241) in the National Archives.

Courtesy of Thomas Edison National Historical Park.