However, this material is very expensive and as a practical filament, its efficiency is limited. Finally, Edison tried the carbonized cotton thread filament. On the evening of Sunday, October 19, 1879, Edison and his assistants electrified the cotton thread and took turns observing around the clock. More than 40 hours later, the cotton filament was still glowing, and Edison knew he had solved the problem. Light bulb sales began in 1880, and the first full introduction of Edison's lighting system in London came as early as the 1882 Holburn Viaduct, where the era of General Electric lighting by concentrating City power was started on September 4, 1882, at the Pierre Avenue station in New York.