What is "mond gas"

Mond gas is a cheap coal gas that was used for industrial heating purposes. Coal gases are made by decomposing coal through heating it to a high temperature. Coal gases were the primary source of gas fuel during the 1940s and 1950s until the adoption of natural gas. They were used for lighting, heating, and cooking, typically being supplied to households through pipe distribution systems. The gas was named after its founder, Ludwig Mond.