34 LIFE AND LIGHT 



neutralised acidic and basic oxides, can stand the heat, and such 

 bodies as the carbonates of the alkaline earths, for example, can be 

 present in an incomplete state of combination, partially oxide and 

 partially carbonate, in labile equilibrium with a varying partial 

 pressure of carbon dioxide in the atmosphere. 



But it is only at a very much lower temperature that compounds 

 at all complicated in structure can exist in equilibrium, and for 

 those compounds of many hundreds of atoms which are character- 

 istic of life the range is narrowly limited. Thus, practically all the 

 life of the planet would be completely destroyed at a temperature 

 which we may place for inclusive purposes at 56 C. At a little more 

 than 10 below this moderate limit all birds and mammalia would 

 have disappeared, and even at 30 C. the vast bulk of cold-blooded 

 creation would have perished. Even the highly organised ferments 

 called enzymes, which still bear half impressed upon them the 

 properties of the living cells from whence they came, begin to suffer 

 rapid deterioration in all cases at about 50 C., and at 60 to 70 

 they are rapidly destroyed. 



We may next note that as the temperature begins on the cooling 

 planet to reach the limit at which sufficient complexity of chemical 

 structure to support life becomes possible, then more and more 

 complex chemical compounds are not only possible of existence, 

 but begin to exist. 



For example, as soon as the temperature will admit of carbonate 

 formation in equilibrium, then carbonates come into existence. 

 In other words, when equilibrium conditions admit of it, matter 

 of its own properties tends where energy is available to take on the 

 complex forms. 



Next in order of development, inorganic colloids begin to arise 

 on the cooling globe. Single molecules existing in solution, and 

 capable of forming colloids with alteration in temperature, begin to 

 form complexes or solution aggregates in which the unit of structure 

 passes from the atom to the molecule. Now instead of single 

 atoms uniting to form simple single molecules, we find molecules 

 behaving as atoms, and uniting with a new order of affinities alto- 

 gether to form colloidal aggregates. 



Accompanying these structural changes the energy types and 

 phases inhabiting the unit of structure also vary. The rates of 

 vibration or of phasic activity in the colloidal aggregates would be 

 slower than in the simpler molecules of the crystalloids. All that has 



