HIS PROGRESSIVE RELATIONS. 165 



active and operative as ever, and if to them we 

 ascribe in any degree the vital changes that have 

 taken place, so through their instrumentality we 

 must look for similar changes to follow. So far as 

 science can determine, there is in nature no abate- 

 ment of force, no change of method ; and it were 

 reversing every principle of reasoning to suppose that 

 under these circumstances life had ceased to diverge 

 or had found its culmination in man. It is true 

 that to whatever process we ascribe the introduction 

 of new species, its operation is so slow and gradual, 

 that centuries may pass away before its results 

 become discernible. But no matter how slow ; time 

 is without limit, and if we can trace a process of 

 variation at work, it is sure to widen in the long run 

 into what are regarded as specific distinctions. It is 

 no invalidation of this argument that science cannot 

 point to the introduction of any new species within 

 the historic era, for, till within a century or so 

 science took no notice either of the introduction or 

 extinction of species, nor was it sufficiently ac- 

 quainted with the flora and fauna of the globe to 

 determine the amount of variation that was taking 

 place among their respective families. Indeed, in- 

 fluenced by the belief that the life of the globe was 

 the result of one creative act, men were unwilling 

 to look at the long past which the infant science of 



