ix.] ON A PIECE OF CHALK. 201 



Choose your hypothesis ; I have chosen mine. I can 

 find no warranty for believing in the distinct creation of 

 a score of successive species of crocodiles in the course of 

 countless ages of time. Science gives no countenance 

 to such a wild fancy ; nor can even the perverse 

 ingenuity of a commentator pretend to discover this 

 sense, in the simple words in which the writer of 

 Genesis records the proceedings of the fifth and sixth 

 days of the Creation. 



On the other hand, I see no good reason for doubting 

 the necessary alternative, that all these varied species 

 have been evolved from pre-existing crocodilian forms, 

 by the operation of causes as completely a part 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 animals, 

 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 



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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 fervent, 



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 " with- 



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out haste, but without rest" of the land and sea, as in the 

 endless variation of the forms assumed by living beings, 

 we have observed nothing but the natural product of the 

 forces originally possessed by the substance of the universe. 



