Thomas Edison did not invent the light bulb — he perfected it: at Menlo Park in October 1879, his carbonized-thread filament burned for more than 13 hours in an evacuated glass bulb, and by 1880 he had the system — bulb, dynamo, wiring, meter. Joseph Swan had shown a working bulb in 1878; Humphry Davy made arc light in 1802.
Edison's true invention was the system, not the bulb: central power stations, parallel circuits, fuses and meters that made electric light cheaper than gas. In 1882 his Pearl Street station lit lower Manhattan — the first grid — and the incandescent age began. Swan and Edison later merged their British interests as Ediswan.
