“Photometric Diagram of Carbon Loop.” Pen and ink drawing with long manuscript caption, Edison’s Laboratory, [Menlo Park, New Jersey], 18 March 1880, signed by Charles L. CLARKE (1853-1941) and inscribed “Note Book 66,” lower right.

One page, 400 x 310mm, on starched drafting linen. (Mild soiling and a few spots, fingerprint.) Custom cloth folder.

An important 1880 manuscript diagram relating to Edison’s electric light bulb, one of the most epoch-changing inventions of the modern era, from the personal collection of Charles L. Clarke, the Chief Engineer and first President of the Edison Electric Light Company. A central, simple line drawing of the iconic glass vacuum tube is surrounded by a diagram showing the amount of illuminated surface around the bulb. Edison built his first high resistance, incandescent electric light in Menlo Park in 1879 but the filaments burned out within just a few hours. Over the next year, he and his team tested thousands of filament materials before finally settling on carbonized cotton. The light bulb as we basically know it today was patented on January 27, 1880, less than three months before the date of this drawing. Such original material is rare. The present is signed by and derives from the collection of Charles L. Clarke who had retained a scrapbook of personal material from his days as one of Edison’s top engineers.

Charles L. Clarke, 1853-1941, first President of the Edison Electric Light Company
Eric C. Caren; sold
Christie's New York, 15 June 2017, lot 300