200 THE WOKLD OE LIFE 



always sinking below it, yet ever being renewed by elevatory 

 forces, whose nature and amount we can only partially deter- 

 mine. Yet these obscure forces have always acted with so 

 much regularity and certainty that the long, ever-branching 

 lines of plant and animal development have never been com- 

 pletely severed. If, on the other hand, the earth's surface had 

 ever reached a condition of permanent stability, so that both 

 degrading and elevating forces had come to a standstill, then 

 the world of life itself would have reached its final stage, and, 

 w^anting the motive power of environmental change, would have 

 remained in a state of long-continued uniformity, of which the 

 geological record affords us no indication whatever. 



Readers of my book on Man's Place in the Universe will 

 remember how, in chapters xi, to xiv., I described the long 

 series of mechanical, physical, and chemical adjustments of 

 the earth as a planet, which were absolutely essential to the 

 development of life upon its surface. The curious series of 

 geological changes briefly outlined in the present chapter are 

 truly supplementary to those traced out in my former work. 

 The conclusion I drew from those numerous cosmic adapta- 

 tions was that in no other planet of the solar system were the 

 conditions such as to render the development of organic life 

 possible upon them — not its existence merely, which is a 

 vastly different matter. That conclusion seemed to many of 

 my readers, including some astronomers, geologists, and 

 physicists, to be incontestable. The addition of the present 

 series of adaptations, whose continuance throughout the whole 

 period of world-life history is necessary as furnishing the mo- 

 tive power of organic development and adaptation, not only 

 increases to an enormous extent the probability against the de- 

 velopment of a similar ^^ world of life," culminating in man, in 

 any other known or reasonably conjectured planet, but af- 

 fords, in my opinion, an exceedingly powerful argument for an 

 overruling Mind, which so ordered the forces at work in the 

 material universe as to render the almost infinitely improbable 



