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CHAP. XX. THE STELLAR EVIDENCE EEGARDING INORGANIC 



EVOLUTION,. 



JUST as plants and animals compose the organic or living world, so do 

 the so-called chemical elements (either single or combined) compose the 

 inorganic or non-living world. 



Formerly plants and animals and the chemical elements were all 

 considered to represent special creations " manufactured articles " ; 

 we now know that plants and animals do not ; that they have been 

 continuously evolved from simpler forms. 



What we have now to consider is whether the facts set out in the 

 preceding chapters do or do not indicate that we must accept the 

 chemical elements, like plants and animals, as products of evolution. 



Taking plants and animals as we know them, the more we dive 

 into past times the more differences in form are noted, though the 

 temperature at which the vital processes were and are carried on have 

 certainly not been widely different. 



Taking the chemical elements as we know them here, we find differ- 

 ences in composition continuously indicated as stars of successively higher 

 temperature are studied. It is obvious that this is a very important 

 point. In inorganic evolution we are dealing with a great running down 

 of temperature ; how tremendous no man can say. We know the tem- 

 perature of our earth, but we do not know, and we cannot define, the 

 temperatures of the hottest stars. So that how great the temperature 

 of the earth may onee have been, supposing it to be represented by the 

 present temperature of the hottest star, no man knows with certainty. 



With regard to organic evolution, however, which has to do with 

 the plant world and the animal world, there can have been no such 

 running down of temperature at all. The temperature must have been 

 practically constant within a very few degrees. 



The differences then depend upon time in organic, and upon tem- 

 perature in inorganic, nature. 



It is for this reason that in the inorganic evolution which now 

 concerns us the chemical changes brought about by changes of tem- 

 perature must be our chief guide, and the earliest and simplest forms 

 must be sought in regions where the highest temperature is present. 



The effect of high temperature in producing simplifications is known 

 to everybody. If we deal, for instance, with well known chemical 



