18 



THE STOEY OP THE EARTH AND MAN. 



but for which I have elsewhere proposed the name 

 " Eozoic/^ or those that afford the traces of the 

 e^-rliest known living beings. These rocks are the 

 Laurentian Series of Sir William Logan, so named 

 from the Laurentide hills, north of the River St. 

 Lawrence, which are composed of these ancient beds, 

 and where they are more largely exposed than in 

 any other region. It may seem at first sight 

 strange that any of these ancient rocks should be 

 found at the surface of the earth ; but this is a 



Fig. 6. The Laurentian nucleus of the American continent. 



necessary result of the mode of formation of the 

 continents. The oldest rocks, thrown up in places 

 into high ridges, have either not been again brought 



