272 THE EVOLUTIONARY CAREER 



Then it has been held, in quite recent years, that the energy 

 that is emitted by a hot star may come from the " annihilation 

 of matter." Protons and electrons, of which material atoms are 

 compounded, may come together in some way and disappear, 

 being converted into high-frequency radiation. But, again, this 

 is emitted into space, is absorbed by other material bodies, and 

 so becomes converted into the low frequency of heat, which again 

 becomes ever more uniformly distributed throughout interstellar 

 space. 



And so, considering the elements of the universal system of 

 things as quanta of energy it appears that the distribution of these 

 quanta, or elements, tends always to become more and more 

 uniform in all regions of space. The probability that we shall 

 find just as much energy in any one block of space as in any 

 other block, taken at random, becomes ever greater. And, looked 

 at in another way, cosmic evolution means that a particular order, 

 or arrangement, that of the concentration of energy in particular 

 minute parts of the cosmos (in the stars) tends to disappear during 

 those physical changes which we see to proceed in the universe. 

 Since all that we call " physical phenomena " are dependent on 

 the existence of these concentrations of energy, or of an initial, 

 particular order, or arrangement, the changes that proceed in the 

 process of cosmic evolution tend toward the cessation of those 

 changes themselves, that is, to an ultimate equilibrium. 



89^. Planetary Evolution. A planet was originally a certain 

 mass of hot vapour extruded by a star as the result of the near 

 approach of another star : the mutual gravitation of the two bodies 

 led to the extrusion of material by one or both of them. This 

 hot material drew together, in spherical form, condensed to a 

 liquid and then to a solid state, cooling all the while. Finally 

 a solid, light, lithospheric envelope, or shell, condensed on a 

 solid, heavy metallic kernel, or centrosphere. Later w^ater con- 

 densed on the lithosphere, or earth-crust, as the hydrosphere, 

 or ocean. Finally an atmosphere came to surround the lithosphere 

 and hydrosphere. Such has been the course of evolution of the 

 earth. 



The inorganic earth-envelopes. We shall now consider the 

 formation of lithosphere, hydrosphere and atmosphere in order 

 to contrast the processes with those by which the biospherey or 

 earth-life, was formed : it will be seen that the contrast of two 



