THE FOUNDATIONS OF THE CONTINENTS 87 



cone, and multitudes of eggs and free-swimming 

 germs of hundreds of kinds of marine animals to 

 re-people the sea-bottom. Whence were such 

 things to come from to occupy the old Archaean 

 hills and sea-basins ? and all our knowledge of 

 nature gives us no answer to the question, except 

 that a creative power must have intervened ; but 

 in what manner we know not. That this actually 

 occurred, we can, however, be assured by the next 

 succeeding geological formation. We have seen 

 that the granitic and gneissic ridges could furnish 

 pebbles, sand, and clay, and these once deposited 

 in the sea-bottom could be hardened into con- 

 glomerate, sandstone and slate. But beside these 

 we have in the next succeeding or Upper Lauren- 

 tian formation rocks of a very different character. 

 We have great beds of limestone and iron ore, and 

 deposits, of carbon or coaly matter, now in the 

 peculiar state of graphite or plumbago, and it is 

 necessary for us to inquire how these could 

 originate independently of life. In modern 

 seas limestone is forming in coral reefs, in shell 

 beds, and in oceanic chalky ooze composed of 

 minute microscopic shells ; but only in rare and 

 exceptional instances is it formed in any other 



