The relationship between energy and water has been important since the dawn of the Industrial Revolution. One of the most important early applications of steam engines was pumping water from coal mines. As miners removed coal near the surface first, mines extended deeper into productive coal seams. In deep mines, water would pool at the bottom of the pit, interfering with the labor of the miners. Pumping water from mines requires tremendous effort, so mining companies used steam engines for the heavy lifting. In this scenario, energy in the form of coal fueled a steam engine using water vapor to provide mechanical energy to pump liquid water so operations could mine more coal.