A DYNAMICAL THEORY OF THE ELECTROMAGNETIC FIELD. 571 



gravitating force, and R the resultant magnetic force at a corresponding part 

 of the field, 



R= -R, and 0: 

 Hence 



07T 



(47). 



The intrinsic energy of the field of gravitation must therefore be less where- 

 ever there is a resultant gravitating force. 



As energy is essentially positive, it is impossible for any part of space to 

 have negative intrinsic energy. Hence those parts of space in which there is 

 no resultant force, such as the points of equilibrium in >the space between the 

 different bodies of a system, and within the substance of each body, must have 

 an intrinsic energy per unit of volume greater than 



where R is the greatest possible value of the intensity of gravitating force in 

 any part of the universe. 



The assumption, therefore, that gravitation arises from the action of the 

 surrounding medium in the way pointed out, leads to the conclusion that every 

 part of this medium possesses, when undisturbed, an enormous intrinsic energy, 

 and that the presence of dense bodies influences the medium so as to diminish 

 this energy wherever there is a resultant attraction. 



As I am unable to understand in what way a medium can possess such 

 properties, I cannot go any further in this direction in searching for the cause 

 of gravitation. 



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