332 THE CAUSES OF THE xi 



notion of the nature of the forces exercised by 

 living beings, we discovered that they if not 

 capable of being subjected to the same minute 

 analysis as the constituents of those beings them- 

 selves that they were correlative with that they 

 were the equivalents of the forces of inorganic 

 nature that they were, in the sense in which the 

 term is now used, convertible with them. That was 

 our general result. 



And now, leaving the Present, I must endeavour 

 in the same manner to put before you the facts 

 that are to be discovered in the Past history of 

 the living world, in the past conditions of organic 

 nature. We have, to-night, to deal with the facts 

 of that history a history involving periods of 

 time before which our mere human records sink 

 into utter insignificance a history the variety and 

 physical magnitude of whose events cannot even 

 be foreshadowed by the history of human life and 

 human phenomena a history of the most varied 

 and complex character. 



We must deal with the history, then, in the 

 first place, as we should deal with all other 

 histories. The historical student knows that his 

 first business should be to inquire into the validity 

 of his evidence, and the nature of the record in 

 which the evidence is contained, that he may be 

 able to form a proper estimate of the correctness 

 of the conclusions which have been drawn from 

 that evidence. So, here, we must pass, in the first 



