THE LIBERATION OF ENERGY 



59 



in the final decomposition of all dead bodies, the 

 oxidised products pass back again to the sources from 

 which they came, in all probability to be rebuilt into 

 the tissues of another generation of green plants. 

 The diagram now before us, aims at showing that 

 a similar generalisation may be arrived at with 

 reference to the circulation of energy in the Universe. 



The solar energy K,NET,C SOLAR ENERGY ' 

 becomes, in part, 4 



stored as potential 

 energy in the organic 

 compounds manu- 

 factured by the green 

 organism. Whether 

 these are oxidised in 

 the green plant itself 

 or in an animal 

 which has used the 

 green plant as food, 



FIG. 23. 



Circulation of energy. 



or in a carnivorous animal 



which has preyed on a herbivorous one, the result 

 is the same ; the energy is gradually released. 

 Before being radiated from the body in its final form 

 as heat (the one form of energy, it will be remembered, 

 into which all other forms are ultimately transform- 

 able), the potential energy of the food makes its appear- 

 ance as mechanical, chemical or electrical energy. The 

 energy, even in its final form, is not " lost," however, 

 but becomes unavailable on its dissipation into space. 

 There is thus both a balance of matter and a balance 

 of energy in the Universe, and these two great generali- 

 sations are among the most important with which 

 modern science has made us acquainted. 



