Matter and Energy 



19 



rents developed, plus the heat energy given off, but not destroyed, 

 by the wires and machinery. 



Source of Energy. Since all matter, whether animal, vege- 

 table or mineral, must have energy in order to change in any way, 

 it is important to know where that energy comes from. 



The sun is the source of all the energy on the earth. Fuel, 

 food, water and wind all derive their energy from the sun's rays. 



International Paper Co. 



THE ENERGY OF STEAM AND THE ENERGY OF FLOWING WATER 

 RUN THIS FACTORY 



The beds of coal from which so much heat energy is obtained 

 represent the work; of the sun in past ages in making the vege- 

 table matter which in time became coal. By the aid of the sun- 

 light, energy is stored in the food which man, animals and plants 

 use. In our bodies much of the energy stored in the foods we 

 eat is utilized as heat, motion and nervous force. Every muscle, 

 like an engine, does work in transforming stored-up energy into 



