CHAPTER IX 

 ENERGY 



IN the preceding chapters certain facts as to the 

 composition of matter have been stated, which may be 

 summarized in the statement that matter is granular 

 in structure and electrical in nature. In all matter 

 we have reason to believe that the constituent parts 

 are in motion. By the motion of electrons the phe- 

 nomenon of contact electrification (cf . page 95) was ex- 

 plained. In later chapters we shall discuss further the 

 motions of the electronic constituents and also of the 

 atomic aggregates which compose the molecules of 

 matter. Of the motions of the molecules themselves, 

 at least in the case of liquids and gases, there is familiar 

 evidence in the phenomenon of diffusion, that is, the 

 unaided mixing of two different substances, of which 

 the diffusion of an odor through air is an example. 



Because of the characteristic of inertia (cf. page 68) 

 there is associated with all the motions of these con- 

 stituents of matter an ability to do work, which we call 

 energy. To say that all bodies in the universe have 

 inertia is to say, in effect, that all moving bodies 

 possess energy, but offers no explanation of the original 

 cause, the energy source of the universe. All the 

 physical explanations of the origin of our earth, or our 

 astronomical system, must start from an assumed con- 



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