These letters, which cover the years 1880-1888, are addressed to Thomas Logan, supervisor of the machine shop at the Menlo Park laboratory. The correspondents include Edison, writing from the New York office of the Edison Electric Light Co., and Charles L. Clarke, chief engineer of the company. Many of the items contain instructions about steam dynamo design, construction, and testing; a few were annotated by Francis Jehl during the 1930s. There is also an undated drawing by Edison of copper tubes enclosed in an alloy cylinder, along with an 1888 letter from John Kruesi describing the manufacture of telephone chalks. Courtesy of the Henry Ford Museum and Greenfield Village Research Center.