CHAPTER XII 



GRAVITATION AND THE PROPERTIES OF MATTER 

 THE KINETIC THEORY AND NATURE OF GASES. 



THE phenomena of Gravitation remain still un- 

 explained. The ordinary conception of gravitation is 

 that it is the attraction or drawing together (from 

 "Attrahere," to draw to) of one body towards another. 

 It seems impossible to explain this drawing action of 

 mass acting upon mass. A solid ether without 

 movement cannot explain it, and the atomic theory 

 of the ether can do little if any more. It is evident, 

 however, that the same movement of two bodies 

 towards each other can be produced by pressure ex- 

 erted from outward towards each other in the straight 

 line of their respective centres. It is probable that 

 in all cases where apparent attraction exists, or even 

 its opposite, repulsion, that the real motive force is 

 that of the pressure of the surrounding medium ; the 

 difficulty is to demonstrate the existence and the 

 cause of the external pressure. The laws or con- 

 ditions under which gravity or the attraction of gravi^ 



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