THE THEORY OF ENERGY AND THE LIVING WORLD. 523 



energy is much in evidence. We shall admit the existence of a latent 

 state, or state of potential chemical energy. In the example just given, 

 the carbon under the preliminary excitation combines with oxygen and 

 forms carbonic acid gas. The potential energy becomes actual energy 

 and immediately is transformed into heat. A very incomplete and 

 fragmentary conception of the matter would be formed if the 

 phenomenon of combustion solely were regarded and it was neglected 

 to inquire after the source of the energy thus dissipated. The ante- 

 cedent fact is the action of the sun upon growing vegetation. The 

 carbon which burns in the furnace of the engine comes from a mine 

 where it was accumulated, in the state of coal, a primitive vegetable 

 product which was formed indirectly from the carbonic acid of the air. 

 By the aid of the solar energy the plant had separated the carbon 

 from the oxygen to which it was united in the carbonic acid of the 

 atmosphere and had created potential chemical energy, which through 

 the lapse of ages awaited its utilization. Combustion dissipated this 

 energy in re-forming carbonic acid. 



The fecundity of the conception of energy is seen from these examples 

 to lie in the connection which it establishes between the phenomena of 

 nature, and that it thus reestablishes a proper articulation, necessarily 

 broken in the ancient analytical view of the sciences. We are led to 

 see in the phenomena of the world nothing but the mutations of energy. 

 In these mutations themselves we see the circulation of an indestructible 

 agent, which passes from one form to another as if it but changed into 

 disguise. If our intellects required images or symbols to embrace the 

 facts and seize upon their import they are at hand. They materialize 

 energy, making of it a sort of imaginary being and conferring upon it 

 a real objectivity. It then becomes for the mind, on condition that the 

 latter does not become the dupe of a phantom itself has raised, an 

 artifice eminently comprehensive, and capable of rendering the greatest 

 assistance in grasping the relation and affiliation of phenomena. 



The world then appears, as we said at the beginning, to be con- 

 structed with singular symmetry. It offers us nothing but mutations 

 of matter and mutations of energy. These two kinds of metamorphoses 

 are governed by two laws similar and necessary, the conservation of 

 matter and the conservation of energy, which these maintain, the first, 

 that matter is indestructible and passes from one phenomena to another 

 in integrity and equality of weight; the second, that energy is inde- 

 structible, and that it passes from one phenomena to the other in rigid 

 equivalence numerically determined by the researches of physicists. 



The first problem of energetics is to examine the different forms of 

 energy, to consider them in their relation to each other, to determine 

 if their mutual transformations can be directly realized, and if so to 

 follow this means to determine their quantitative equivalence. This is 

 a laborious task, which extends over the whole field of physics. 



Such an examination suffices to show that mechanical energy may be 



