By the assist of the two factors -increased population and migration of farmers -, especially during the 1700s to the 1800s, the population of the urban area increased rapidly such as during the 1850s, urban population of Britain over half of the whole population.
Since the urbanization, factory owners could employ their laborers in cheap salaries because of the competition between the employees and unemployees, they got an enlarged profit, and as a result, factory owners invested in their way of using energy which naturally led to the energy revolution and improved irons. For an example of these, in 1712, Thomas Newcomen developed a steam engine powered by coal, in 1764, James Watt made improvements on the engine and more efficient and simultaneously, in 1709, Abraham Darby used coal instead of charcoal to smelt iron. By those improvements and circumstances, factories became mechanized and stepped into an industrial revolution, which totally changed the lives of commoners as factory workers whether their gender or age was.