THE CAUSE OF GRAVITATION 



possible distances between the stars, and if perfectly 

 elastic would retrace their paths in the reverse direc- 

 tion. As gravitation acts inversely as the square of 

 the distance, and as the nearest star is at least 300,000 

 times farther from the sun, and probably from other 

 stars, than the earth is from the sun, gravitation be- 

 tween the nearest star and the earth would be only 

 one ninety thousand millionth (ao^oopoo) P ar * of the 

 force that holds the earth in its orbit around the 

 sun. We know that gravitation acts between these 

 remote stellar suns and their planets: it is shown 

 by the occlusion of light in the instance of the so- 

 called variable stars, caused, beyond question, by a 

 large planet interposing itself between the star and 

 our line of vision. The phenomena of the double 

 stars may also have a like explanation ; but too little 

 is known as yet concerning them to formulate a 

 theory thereon. Before further considering the 

 dynamic action of gravity it is necessary to give a 

 short statement of the PHYSICAL CONSTITUTION 



OF MATTER. 



All matter is believed to be composed of molecules, 

 or groups of atoms, of a determinate character, shape 

 and size, which, though minute, far below our power 

 of vision aided even by any microscope, are yet vastly 

 larger than the atoms that compose the ether. 



The atoms of matter are the chemical atoms or 

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