Gas companies such as the Gas Light and Coke Company were established in London from as early 1812. Gas was principally used for domestic, commercial and street lighting; usage for cooking and heating were developed throughout the nineteenth century. Gas was made by roasting or carbonising coal which drove off a mixture of flammable gases, principally methane, hydrogen and carbon monoxide. The ‘town gas’ as it was called was stored in large gas holders and distributed to consumers in iron pipes. The carbonisation process also produced valuable by-products such as coke, coal tar and ammoniacal liquor.