At Menlo Park, on the site of Thomas Alva Edison's experimental laboratory, Edison tested the first practical incandescent lamp on October 21, 1879, after innumerable unsuccessful experiments with filaments, producing a carbonized cotton thread lamp in a highly exhausted glass bulb powered by Bunsen cells that glowed for forty consecutive hours. From 1876 to 1886, this laboratory was the place where many of Edison's important inventions were made, including improvements that led to a commercial incandescent lamp, the first dynamo-electric generator with a shunt field winding and low-resistance armature, constant-voltage central station equipment, the first parallel electric distribution system, underground city electric conduits, switches, meters, fuses, high-tension direct-current transmission and distribution systems, an experimental electric railway motor and locomotive, electric railway power systems, the harmonic and quadruplex telegraph systems, wireless communication and telegraphy methods, the Edison Effect, telephone transmitters and receivers, and the phonograph. In 1886 the laboratory's contents were moved to Orange, New Jersey, where Edison continued his work, while the laboratory building itself was transported in 1929 by Henry Ford to Dearborn, Michigan. On October 21, 1929, during the jubilee celebration of the lamp's invention, Edison lighted a lamp in the tower's interior from Dearborn, and a large light atop a temporary tower on the site was also lighted by him and burned nightly until lightning destroyed that tower on August 11, 1937, as a permanent tower erected in 1937 was being built around it.
