DISPLACEMENT 



PROPOSITION XVIII. 



Force cannot be transmitted from one body to 

 another body, which is in all respects equal to the 

 first body. 



Let the circle A represent a body in all respects 

 equal to the body represented by the circle B. 



And let a force be transmitted through the small 

 bodies represented by the dots. 



Then it is evident that if B is in all respects 

 equal to A, it is, also, equal in that which tends 

 to transmit force, from A to B, and the tendency 

 will be equally strong to transmit force from B 

 to A. 



Let the force to be transmitted from A to B be 

 that manifestation of force to us known as elec- 

 tricity. 



Then, if A and B are both balls of pure copper 

 and equal in size and form, both charged with 

 positive electricity of the same intensity, there will 

 be no exhibition of electrical energy until a third 

 inequal body is brought in contact. 



When the water below the mill dam gets as high 

 as it is above the dam, there is no more power. 



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