Early peoples learned how to use flowing water to do work. Water was used to power water mills and to provide irrigation for farming. Later, people were able to use liquids to do even more after scientists learned that all liquids follow certain rules. They learned that pressure in a liquid is transmitted equally in all directions. That is, when one pushes down on the liquid in a tube the liquid will push against whatever it comes up against, even if it is bigger than the original tube. Therefore, it is possible to use a small amount of force to create a larger force somewhere else.