230 WALKS AND TALKS. 



early precipitation. We find other traces in the conglom- 

 erates embraced in the old Eozoic rocks. We even find traces 

 in the slaty character of many of the pebbles, since much 

 alumina and silicate of alumina must have been liberated in 

 the progress of the chemical conflict, as already explained. 

 So when, at the end of the Eozoic ^Eon, vast beds were up- 

 raised which stand to our times, they were not the first land, 

 but only the first land which has survived to the human era. 



XL/. THE WORLD \VITHOUT A. BACKBONE. 



REIGN OF INVERTEBRATES. 



WE have followed the train of events down to a time 

 when the work of the geologic forces had become settled to 

 the tenor which was to be maintained through all the later 

 seons. Uplift, erosion, sedimentation are the key-words to the 

 physical history of the world; and these all express mere 

 sequences of a more fundamental action, COOLING. We are 

 DOW contemplating the world as it existed during the aeon 

 designated Eozoic. I think, for reasons already stated, that 

 even then some areas of sea-bottom had been upraised to serve 

 as sources for the clearly fragmental materials laid down to 

 become Eozoic rocks. Where those crumbling lands were 

 located, we can not well conjecture. There may have been 

 clear, sun-lighted cliffs, beaten at times by dripping rains, 

 corroded by breaking waves all as in the human epoch. The 

 same mineral substances resisting the agencies of destruction ; 

 the same quality of sun-light, the same breeze blowing up 

 from the sea, the same ceaseless roar of the battle along the 

 beach. But it was a reign of the physical forces alone. The 

 wide sea was without a tenant; there were no bleached shells 

 strewn along the beach. No shrub contended with the surf 

 for the possession of the sandy foothold ; and no tree, how- 

 ever humble, held safer possession of the sparse soil gathered 

 in the chinks of the knotted cliffs. There was no form of 

 living creature seeking the ends of its being over all the 



