CHAPTER III. 



THE PEIMOEDIAL, OE CAMBRIAN AGE. 



BETWEEN the time when Eozoon Canadense flourished 

 in the seas of the Laurentian period, and the age 

 which we have been in the habit of calling Primor- 

 dial, or Cambrian, a great gap evidently exists in our 

 knowledge of the succession of life on both of the 

 continents, representing a vast lapse of time, in which 

 the beds of the Upper Laurentian were deposited, and 

 in which the Laurentian sediments were altered, con- 

 torted, and upheaved, before another immense series 

 of beds, the Huronian, or Lower Cambrian, was formed 

 in the bottom of the sea. Eozoon and its companions 

 occur in the Lower Laurentian. The Upper Lauren- 

 tian has afforded no evidence of life ; and even those 

 conditions from which we could infer life are absent. 

 The Lowest Cambrian, as we shall see, presents only 

 a few traces of living beings. Still, the physical 

 history of this interval must have been most impor- 

 tant. The wide level bottom of the Laurentian sea 

 was broken up and thrown into those bold ridges 

 which were to constitute the nuclei of the existing 

 continents. Along the borders of these new-made 

 lands intense volcanic eruptions broke forth, produ- 

 cittg great quantities of lava and 'scoriae and huge 

 beds of conglomerate and volcanic ash, which are 



