ENERGY AND ITS TRANSFORMATIONS. 



25 



from mass-energy to molecular energy of any kind, or 

 from one form of molecular energy to another, with a 

 definite quantivalence. 



These laws lead to the conclusion that, in any iso- 

 lated system of bodies, or in any isolated mass, the 

 total of all energy present is always the same ; though 

 it may be transformed in various ways, and to an ex- 

 tent only limited by the special conditions affecting the 

 system. They lead to the conclusion that energy of 

 higher intensity than the mean must occupy a limited 

 space, and will continually tend to dissipate itself by 

 dissemination through a greater volume, affecting 

 larger and larger quanties of matter, with proportional 

 reduction of intensity, until the whole system is occu- 

 pied by the originally existing energy, at a finally uni- 

 form and minimum intensity. Energy confined within 

 a limited space thus continually tends to expand, and 

 to break through its boundaries, and, if not freed from 

 this constraint, it produces a pressure upon the sur- 

 rounding surfaces, which, e.g., is exhibited as tension 

 of enclosed vapors and gases. Freed from confine- 

 ment, it tends to indefinitely expand. 



Either form of energy may produce either other form 

 under suitable conditions. 



Rankine's statement of the " General Law of the 

 Transformation of Energy" is as follows : 



*'The effect of the whole actual energy present in a 

 substance, in causing transformation of energy, is the 

 sum of the effects of all its parts." 



The axiom, as Rankine calls it, that " any kind of 

 energy may be made the means of performing any kind 



*Proc. Phil. Soc. of Glasgow ; vol. iii. No. 5 ; 1853. 



