THE BEGINNINGS OF LIFE 



mal means as we have at command. Speaking 

 generally, the most complex compounds are the 

 most unstable, and these are the soonest decom- 

 posed by heat. The highly complex organic 

 molecules of fibrine and albumen are often 

 separated by the ordinary heat of a summer's 

 day, as is witnessed in the spoiling of meat. 

 Supersalts and double salts are decomposed at 

 lower temperatures than simple salts ; and these 

 again yield to a less amount of heat than is re- 

 quired to sunder the elements of deutoxides, 

 peroxides, etc. The protoxides, which are only 

 one degree more complex than simple elements, 

 withstand a still higher temperature, and sev- 

 eral of them refuse to yield to the greatest heat 

 which we can produce artificially. No chemist, 

 however, doubts that a still greater heat would 

 decompose even these. 



We may thus picture to ourselves the earth's 

 surface as at the outset composed only of un- 

 combined elements, of free oxygen, hydrogen, 

 nitrogen, carbon, sulphur, etc., and of iron, 

 copper, sodium, and other metals in a state of 

 vapour. With the lowering of this primitive 

 temperature by radiation, chemical combinations 

 of greater and greater heterogeneity became 

 gradually possible. First appeared the stable 

 binary compounds, such as water and the in- 

 organic acids and bases. After still further low- 

 ering of temperature, some of the less stable 



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