HOW LIFE CAME TO EARTH 187 



ture allowed sufficient complexity of chemical 

 structure for life to be borne upon the earth, 

 then life appeared. 



This note cannot be too strongly sounded 

 that as matter is allowed capacity for assuming 

 complex forms those complex forms appear. 

 As soon as oxides can be there, oxides appear : 

 when temperature admits of carbonates, then 

 carbonates are forthwith formed. These are 

 experiments which any chemist can to-day 

 repeat in a crucible. And on a cooling planet, 

 as soon as temperature will admit the presence 

 of life, then life appears as the evidence 

 of geology shows us. But the latter cannot 

 as yet be repeated by the chemist because the 

 conditions of chemical complexity are too 

 delicate, and the colloids begin to show their 

 characteristic slowness of reaction and delicacy 

 of balance. 



Next in order of development prior to life, 

 inorganic colloids begin to appear in solution, 

 or suspension, in the waters of the cooling 

 globe, alumina and silica deposited in colloidal 

 form are seen in many sedimentary rocks. 

 Single molecules existing in solution, and 

 .capable of forming colloids, with alterations 

 in temperature, and in chemical reaction of 

 the environment, begin to form complexes, 

 or solution aggregates, in which the unit of 



