ガス灯
The most important use of manufactured gas in the early 19th century was for gas lighting, as a convenient substitute for candles and oil lamps in the home. Gas lighting became the first widespread form of street lighting. For this use, gases that burned with a highly luminous flame, "illuminating gases", were needed, in contrast to other uses (e.g. as fuel) where the heat output was the main consideration. Accordingly some gas mixtures of low intrinsic luminosity, such as blue water gas, were enriched with oil to make them more suitable for street lighting.