Trees, like other living things, possess two essential elements: carbon and hydrogen. With the help of oxygen in the air, both these elements burn easily when set alight. In primitive times wood was man’s main source of light and heat. Fire was also used to scare wild animals away. People would set light to wood by rubbing two stones together to make a spark.
Now, although we have other sources of fuel, it is still very pleasant to sit by a log fire in the winter