LIFE AND THE COSMOS 303 



ent form of our universe as the result of a 

 gradual evolution from an earlier unknown 

 form, the development of successive solar 

 systems being mere incidents of the larger 

 process, the evolution as a whole directively 

 governed by the law of the degradation of 

 energy. 



A 



THE PERIODIC SYSTEM 



In either hypothesis the remarkable sys- 

 tematic relationship between the elements 

 which is manifest in the periodic classifica- 

 tion has a peculiar place. If the second hy- 

 pothesis be accepted, there seems to be little 

 room for doubt that at an early period the 

 chief cosmic process was the evolution of the 

 elements themselves ; and in the first theory 

 the nebula, whose properties depend almost 

 wholly upon chemical constitution and chem- 

 ical and molecular energy, occupies a unique 

 position, like the leaf in the organic cycle, 

 or spring among the seasons. Thus, whether 

 or not the periodic system is to be regarded 

 as the one remaining plain result of a process 

 bv which the elements were evolved, at least 

 it takes precedence over the other properties 

 of matter, and lies at the very foundation of 

 the known processes of evolution. Clearly, 



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