238 WH AT IS LIFE 



3. The change from (probable) faint light or, 

 perhaps, mere heat from the sun to direct sunlight. 



How completely the presence of life on the earth 

 is dependent upon the sun, is known to everyone. 

 Since, as now known, the sun pours torrents of elec- 

 trons upon the earth, and sunlight exerts actual 

 pressure,^'' the enormity of this change is evident. 



All these causes, of course, are interrelated and 

 were interactive. 



4. The great periods of convulsions and upheaval 

 with their changes of the earth's surface. 



The untold significance of these times as mighty 

 factors in determining the possibility of the appearance 

 of higher life-forms, remains to be realized. 



Heretofore it has been thought and taught (by 

 those who believe that all existing life-forms are 

 descended from the first and lowliest forms of life 

 on the early earth — by practically "everybody") that 

 life advanced in spite of these disturbances. Of 

 course, all pelagic and bathybic forms were unaffected 

 by changes of continental surfaces, and flourished as 

 temperature conditions permitted. Undoubtedly 

 "many new forms have appeared (or 'evolution has 

 gone on') in the sea." Possibly numerous surviving 

 forms, through adaptation to changed environments, 

 suffered modifications because of these disturbances. 



" J. H. Poynting, The Pressure of Light. 



