THE ORGANIC AND THE INORGANIC 297 



motion of its own. It does not matter that the silicates, 

 carbonates, oxides, and all other mineral substances 

 that we now know existed then in the form of chemical 

 elements, or the precursors of chemical elements : all 

 the material bodies now present in the solar system 

 were present in the original nebula. The energy of this 

 nebula consisted of the potential energy represented by 

 the separation of atoms which later on became com- 

 bined together, and of the kinetic energy of motion of 

 these atoms ; and this material and energy, together 

 with the other cosmic bodies radiating energy to it 

 and those bodies receiving the energy which it lost by 

 its own radiation, constituted a system, in the sense of 

 the term as it is employed by the physicists. Now, in 

 the process of cosmic evolution this system became 

 transformed, because it was continually losing energy 

 by radiation. As it cooled, the mean free paths of its 

 atoms and molecules became less and less, and finally 

 condensation to the liquid and then to the solid con- 

 dition occurred. The parts of the nebula continually 

 gravitated together, so that it became smaller and 

 smaller while its rotatory motion became greater. 

 Finally, mechanical strains became set up in its mass 

 as the consequence of the increased velocity of rotation, 

 and disruption occurred with the formation of the sun, 

 the planets, and the satellites. There was no increase of 

 complexity of the system. At any moment of time its 

 elements, that is, the chemical atoms composing it 

 and the energy of these atoms, was the same as at any 

 other moment of time. Heat-energy may have been 

 radiated from one part of the system — the heated 

 nebula — to some other part of the system — the other 

 cosmic bodies absorbing this radiation, but the total 

 energy of the system remained the same. The chemical 

 atoms may have combined together to form molecules 



