ix.] ON A PIECE OF CHALK. 175 



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 &quot; without haste, but 

 without rest &quot; 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. 



