The Elmer Sperry papers contain a complete record of his published patents and his laboratory notebooks. These notebooks, which do have some gaps, can be used to trace the evolution of Elmer Sperry's approach to arc lighting, street railways, electrochemistry, gyroscopic technology, internal combustion engines, and the technological problems he encountered with each of these projects. Sperry was very articulate in his diaries and explored a variety of technological and scientific issues in them. It is evident that he drew on the work of a number of academic physicists and mathematicians and tried to apply their insights to experimental problems. Sperry's diaries contain a large number of sketches which reflect an appreciation of modern science. However, the diaries also show that in many ways Sperry was a nineteenth-century artist-engineer rather than a modern scientist whose insights are based on mathematical models.