INDESTRUCTIBILITY OF FORCE. 



251 



The Indestructibility of Force. So with energy. We 

 cannot create it and we cannot destroy it. We d.erive our 

 energy from the food we eat. And this food we get directly 

 or indirectly from the vegetable kingdom. 



An engine gets energy from the combustion of fuel. In 

 the growth of the plant under the influence of sunlight the 



ANIMALS 



AND PLANTS NOT 

 POSSESSING CHLOROPHYLL 



WHICH DISINTEGRATE 

 COMPLEX CHEMICAL COM- 

 POUNDS, LIBERATING 

 ENERGY IN THE 

 PROCESS. 



PLANTS 

 POSSESSING CHLOROPHYLL 



INTEGRATE COMPLEX 



CHEMICAL COMPOUN 



STORING UP SOLAR ENERGY 



IN THE PROCESS, 



THEY 



Solar Energy 



Energy originally obtained from the sun radiated 

 by the animal (chiefly) into space as heat, and 

 thereby becoming ultimately unavailable. 



Fig. 77. /fetation of Plants and Animals. 



plant has stored up energy. Now that the wood or coal are 

 burned the energy is given out, primarily as heat. But we 

 may convert the heat into electricity, the electricity into light, 

 or back again into heat if we wish. We get our energy from 

 food as the engine gets its energy from fuel. This is saying 

 nothing against the superiority of the human body, and is 

 not in the least degrading. We are self-maintaining, self- 

 directing, growing, living machines. Still, starvation soon 

 puts an end to our ability to produce energy of any kind. 



Now, it is a well-recognized fact that in very many ma- 

 chines only the smaller part of the energy is directed to the 

 end sought. Take a common candle. We wish to get light 

 from it. But most of the energy of the candle is devoted 



