OF GEOLOGICAL DYNAMICS. 121 



become warm by the conversion of mutual poten- 

 tial energy, whether of gravitational, or gravita- 

 tional and chemical, attraction between its parts, 

 into heat. 



36. It may be said, why not admit previous 

 kinetic energy without limit, as we have no reason 

 to believe that the antecedent condition of the 

 matter now constituting the earth was a condition 

 of rest rather than a condition of motion ? I 

 answer that we know nothing of absolute motion 

 or rest in the universe, and that any great degree 

 of relative motion of different portions of matter 

 through space, renders the chances of their hitting 

 one another very small. I therefore say it is not 

 probable that the portions of matter now consti- 

 tuting the earth had in their antecedent condition 

 any great amount of relative motion ; and it is 

 probable that the kinetic energy which was con- 

 verted into heat in their coalition was the equivalent 

 of kinetic energy acquired by mutual gravitation. 

 It seems, indeed, that Kant's " attempt to account 

 " for the constitution and mechanical origin of the 

 " universe, on Newtonian principles," only wanted 



