86 ON A PIECE OF CHALK 1 



/ 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 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 no- 

 wise 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 assumed by living beings, we have 

 V observed nothing but the natural product of the 

 'forces originally possessed by the substance of the 

 i mi versa 



