72 ON A PIECE OF CHALK 



of the common order of nature, as those which have 

 effected the changes of the inorganic world. 



Few will venture to affirm that the reasoning which 

 applies to crocodiles loses its force among other ani- 

 mals, or among plants. If one series of species has 

 come into existence by the operation of natural causes, 

 it seems folly to deny that all may have arisen in the 

 same way. 



A small beginning has led us to a great ending. If I 

 were to put the bit of chalk with which we started into 

 the hot but obscure flame of burning hydrogen, it 

 would presently shine like the sun. It seems to me that 

 this physical metamorphosis is no false image of what 

 has been the result of our subjecting it to a jet of fer- 

 vent, though nowise brilliant, thought to-night. It has 

 become luminous, and its clear rays, penetrating the 

 abyss of the remote past, have brought within our ken 

 some stages of the evolution of the earth. And in the 

 shifting "without haste, but without rest" of the land 

 and sea, as in the endless variation of the forms as- 

 sumed by living beings, we have observed nothing 

 but the natural product of the forces originally pos- 

 sessed by the substance of the universe. 



