Here, Robin Longbottom examines how mills produced their own gas to provide lighting after the use of candles came to an end FROM the very onset of the Industrial Revolution, mills operated 24 hours a day for six days a week. In the 18th and early 19th centuries during the hours of darkness, candles were the main source of light and huge quantities were required. This form of lighting brought its own dangers and mill fires were not uncommon. The most notorious was at Colne Bridge, near Huddersfield, in 1818 when seventeen girls aged from nine to 18 years old lost their lives in a fire thought to have been caused by a candle falling over.