CONTINUITY IN EVOLOTTON. 103 



effects; until at length there have arisen meteorological 

 actions, and consequent geological actions, such as those we 

 now know : determined partly by the Sun s heat, partly by 

 the still-retained internal heat of the Earth, and partly by 

 the action of the Moon on the ocean? How have we 

 reached these geological phenomena ? When did the astro 

 nomical changes end and the geological begin ? It needs 

 but to ask this question to see that there is no real division 

 between the two. Putting pre-conceptions aside, we find 

 nothing more than a group of phenomena continually com 

 plicating under the influence of the same original factors ; 

 and we see that our conventional division is defensible only 

 on grounds of convenience. Let us advance a stage. As 

 the Earth s surface continues to cool, passing through all 

 degrees of temperature by infinitesimal gradations, the for 

 mation of more and more complex inorganic compounds 

 becomes possible ; later its surface sinks to that heat at 

 which the less complex compounds of the kinds called 

 organic can exist; and finally the formation of the more 

 complex organic compounds becomes possible. Chemists 

 now show us that these compounds may be built up synthe 

 tically in the laboratory each stage in ascending complexity 

 making possible the next higher stage. Hence it is inferable 

 that, in the myriads of laboratories, endlessly diversified in 

 their materials and conditions, which the Earth s surface 

 furnished during the myriads of years occupied in passing 

 through these stages of temperature, such successive syn 

 theses were effected ; and that the highly complex unstable 

 substance out of which all organisms arc composed, was 

 eventually formed in microscopic portions : from which, by 

 continuous integrations and differentiations, the evolution 

 of all organisms has proceeded. Where then shall we draw 

 the line between Geology and Biology? The synthesis of 

 this most complex compound, is but a continuation of the 

 syntheses by which all simpler compounds were formed. 



