Thomas Edison of the Edison patent to charge a more reasonable rate for the use of the Edison patent rights and lowering the price of the electric lamp. On October 8, 1883, the US patent office ruled that Edison's patent was based on the work of William E. Sawyer and was, therefore, invalid. Litigation continued for nearly six years, until October 6, 1889, when a judge ruled that Edison's electric light improvement claim for "a filament of carbon of high resistance" was valid. To avoid a possible court battle with Joseph Swan, whose British patent had been awarded a year before Edison's,
John White Howell on display at the Edison exhibit of the General Electric Company were displayed two of the "tar putty" carbon filament lamps made by John W. Howell for the 1890 trial, as well as the tools used by Howell to make said lamps. Seven of Mr. Howell's hand-made 1890 patent trial "tar putty" lamps survive today in a collection of rare, historic lamps discovered in 2004. In 1893 Mr. Howell was appointed chief engineer of the Edison Lamp Works of the General Electric Company, which had taken over the Edison lamp works, holding that position until his retirement in 1931. From