206 THE PHENOMENA OF MOTION 



If we alter the arrangement of the elements, we are 

 able to separate the constituents of a compound by 

 means of another active body ; while the same ele- 

 ments, united in their original order, would have 

 opposed an invincible resistance to the action of the 

 decomposing agent. 



In the same way as two equal inelastic masses, 

 impelled with equal velocity from opposite points, 

 on coming into contact are brought to rest ; in the 

 same way, therefore, as two equal and opposite mo- 

 menta of motion mutually destroy each other ; so 

 may the momentum of force in a chemical com- 

 pound be destroyed in whole or in part by an equal 

 or unequal, and opposite momentum of force in a 

 second compound. But it cannot be annihilated 

 as long as the arrangement of the elementary 

 particles, by which its inherent force was mani- 

 fested, is not changed. 



The chemical force of sulphuric acid is present 

 in sulphate of lime as entire as in oil of vitriol. It 

 is not appreciable by the senses ; but if the cause 

 be removed which prevented its manifestation, it 

 appears in its full force in the compound in which 

 it properly resides. 



Thus the force of cohesion in a solid may disap- 

 pear, to the senses, from the action of a chemical 

 force (in solution), or of heat (in fusion), without 

 being in reality annihilated or even weakened. " If 

 we remove the opposing force or resistance, the force 

 of cohesion appears unchanged in crystallization. 



