For millions of years the only source of energy for human beings was their own physicalstrength. Then about a million and a half years ago they learned to make fire. They learnt to produceheat energy by burning wood. This helped them to warm themselves. It also helped them to cooktheir food and harden the articles they made by potterysail. The cloth sails they put up caught the wind and gave the boats direction. In ancient timesAbout 3200 B.C., the Egyptians learned to use the energy of the wind to make their boatspeople even learned how to harness the power of falling water from water wheels. These were usedmainly for providing water to farms for irrigation.Until the late 1700's, wood was the most important fuel. People used wood so much thamany forests were cut down and trees began disappearing. In time coal took the place of wood. Thegrowing demand for coal brought a search for better mining methods.How did ho title of this passage ​