CONSTITUENTS OF THE UNIVERSE. 



ary motions that approach in point of speed 

 the primary motions of the earth. 



We shall discover that the objects moved 

 can move in only one direction from the oper- 

 ation of a single force. 



Also that such examples of this movement 

 must have a base of operations, or foot-hold, 

 as it were. 



Let us now see how these requirements and 

 conditions meet the case of 



THE MOVEMENTS OF THE MOON. 



That motion is nearly one hundred 



times swifter than the movement of a 

 rifle ball, and is unceasing and regular; while 

 the other movement is brief and irregular. It 

 requires the equivalent of two of these forces 

 in the case of the rifle ball, to produce its 

 simple movement. How would it be then with 

 the moon's peculiar motion, and what possible 

 forces could be applied to such a movement? 

 In the first place the moon has a motion in 

 common with the sun's path, which is prob- 



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