In 1879, Edison's long series of experiments testing materials for suitability as an electric light filament reached a turning point. Charles Batchelor, working at Edison’s Menlo Park laboratory, produced illumination for 14½ hours from a lamp using a carbonized cotton thread. It failed when extra power was added. However, this was such a substantial improvement, attention turned to improving the carbonized filament. Patents were filed, and within two months the progress with the Edison light bulb was made public. An article was published on 21 Dec by the New York Herald. By then, the Menlo Park laboratory was continuously illuminated by Edison's incandescent light bulbs.«