24 FKAGMEXTS OF SCIENCE. 



passed any point, the tension previously in store at that 

 point disappears, but not without having added, during the 

 infinitely small duration of its action, a due amount of 

 motion to that previously possessed by D. The nearer D 

 approaches to F, the smaller is the sum of the tensions re- 

 maining, but the greater is the living force ; the farther D 

 is from F, the greater is the sum of the unconsumed ten- 

 sions, and the less is the living force. Now the principle 

 of conservation affirms not the constancy of the value of the 

 tensions of gravity, nor yet the constancy of the vis viva, 

 taken separately, but the absolute constancy of the value 

 of the sum of both. At the beginning the vis viva was 

 zero and the tension area was a maximum ; close to F the 

 vis viva is a maximum, while the tension area is zero. At 

 every other point the work-producing power of the particle 

 D consists in part of vis viva and in part of tensions. 



If gravity, instead of being attraction, were repulsion, 

 when the particles are in contact, the sum of the tensions 

 between two material particles D and F would be a maxi- 

 mum, and the vis viva zero. If D, in obedience to the 

 repulsion, moved away from F, vis viva would be gener- 

 ated ; and the farther D retreated from F the greater 

 would be its vis viva, and" the less the amount of tension 

 still available for producing motion. Taking repulsion into 

 account as well as attraction, the principle of the conserva- 

 tion of force affirms that the mechanical value of the ten- 

 sions and vires vivce of the material universe is a constant 

 quantity. The universe, in short, possesses two kinds of 

 property which are mutually convertible, at an unvarying 

 rate. The diminution of either carries with it the enhance- 

 ment of the other, the total value of the property remain- 

 ing unchanged. 



The considerations that we have here applied to gravity 

 apply equally to chemical affinity. In a mixture of oxygen 

 and hydrogen the atoms exist apart, but by the application 



