Which invention was made by both Joseph Swan and Thomas Edison?

Though Thomas Edison is usually credited with the invention of the light bulb, the famous American inventor wasn't the only one who contributed to the development of this revolutionary technology.

In 1860, English chemist Joseph Swan had developed a light bulb that used carbonized paper filaments in place of ones made of platinum. Swan received a patent in the United Kingdom in 1878, and in February 1879 he demonstrated a working lamp in a lecture in Newcastle, England, according to the Smithsonian Institution. Like earlier renditions of the light bulb, Swan's filaments were placed in a vacuum tube to minimize their exposure to oxygen, extending their lifespan. Unfortunately for Swan, the vacuum pumps of his day were not efficient as they are now, and while his prototype worked well for a demonstration, it was impractical in actual use.

Edison realized that the problem with Swan's design was the filament. A thin filament with high electrical resistance would make a lamp practical because it would require only a little current to make it glow. He demonstrated his light bulb in December 1879. Swan incorporated the improvement into his light bulbs and founded an electrical lighting company in England. Edison sued for patent infringement, but Swan's patent was a strong claim, at least in the United Kingdom, and the two inventors eventually joined forces and formed Edison-Swan United, which became one of the world’s largest manufacturers of light bulbs.