IDENTICAL CHANGES 



it had first received, and the receiving body, being 

 unable to store up force, must again transmit it. 



We can trace identical manifestations of force, 

 heat for instance, back through many changes in 

 surrounding material, and forward through many 

 changes that follow the original manifestation of 

 heat; but nowhere can we find a material, being 

 changed by heat, that does not by its own change 

 produce farther change. 



We trace every manifestation of force on earth 

 back to the sun ; but does not the sun receive while 

 it gives, and does not the earth give while it re- 

 ceives ? 



Both sun and earth are surrounded by void 

 matter, and in that same continuous void matter 

 float millions of stars that shine upon the earth. 

 And because we see their light we know that mate- 

 rial must pass from each one of them to us. (Prop. 

 XVII, B. 1.) 



The sun that holds the earth in the grasp of 

 gravity is again held and influenced by other 

 stars, for the sun also moves, not in a straight 

 line but in an orbit. 



There are changes upon the sun; clearly our 

 astronomers can observe them; but can the sun 

 change his own spots? 



Because the primary spheres of void matter 

 penetrate all substance, and because all that part 

 of the Universe not filled with organized matter 

 is occupied by a continuous mass of void matter, 

 therefore the spheres of void matter are eyery- 



95 



