524 THE THEORY OF ENERGY AND THE LIVING WORLD. 



transformed into all the other forms and all the other forms into it, 

 with one exception, that of chemical energy. Our knowledge of the 

 role of pressure in dissociation reactions seems at first to abolish this 

 restriction. But this appearance is deceptive. The pressure does not 

 enter into this operation except as a preliminary condition or incentive, 

 merely putting the bodies in such a state relative to each other that 

 chemical affinity can come into play. 



In connection with the calorific and luminous forms of radiant energy 

 it should be noted that they are not as distinct as was believed by 

 the older physicists. To consider the matter objectively, there is no 

 light without heat. It is the same agent which at a certain interval in 

 its scale differently impresses the skin and the retina of men and ani- 

 mals. The difference in sensation is to be imputed to the diversity of 

 the organ, not to the diversity of the agent. At lesser degrees of 

 activity this agent exercises no effect either on the terminations of the 

 thermal nerves of the skin or on the retina. As its degree of activity 

 augments (infra-red heating) the thermal nerves are first impressed, 

 and quite to the exclusion of the nerves of vision. Next both are 

 impressed (sensation of light), and finally the sight only is affected. 

 The transformation of energy therefore reduces itself in this case to 

 the possibility of intensifying or diminishing the action of the common 

 agent to such conditions as suit the passage from one state to another, 

 and this may easily be brought about. 



It may be remarked that this form of energy of which we have been 

 speaking can not be transformed directly into chemical energy. To be 

 sure, radiant energy favors and determines many chemical reactions, 

 but if we go down into the root of the thing we must admit that the 

 radiation serves only to incite the phenomena, to prepare for the 

 chemical reaction, to put the bodies into such a state (liquid, perhaps, 

 or vapor) or temperature (400 for instance in the combination of oxygen 

 and hydrogen) as suits the entrance upon the scene of chemical affinity. 

 On the contrary, chemical energy may be transformed into heat and 

 radiant energy, as could be illustrated by numerous examples in which 

 no other forms of energy are present, and by others where, as in the 

 combustion of hydrogen and carbon, or in explosive decompositions, 

 reactions continue of themselves when once initiated. 



Other restrictions appear in studying the laws which govern the 

 transformations and transference of heat energy, the most important 

 of which maintains the impossibility of heat transfer from a body at a 

 lower to a body at a higher temperature. As the result of all these 

 restrictions heat is an imperfect form of the universal energy, or, as it 

 is expressed by the English, a degraded form. 



On the other hand, electrical energy represents a perfect and highly 

 advantageous form of this universal energy, and this explains the 

 immense development which has taken place in its industrial applica- 

 tion within less than a century. Not that it is better known thau the 



