72 WALKS AND TALKS. 



Now, with this preparation of mind, permit me to state 

 what has been ascertained by studying the fossils imbedded* 

 in the succession of strata. The deepest rocks of which we 

 have any knowledge are those already named Eozoic. They 

 are mostly hard and crystalline such as we find in our in- 

 numerable bowlders. They were stratified originally, never- 

 theless ; they were marine sediments, and if any marine crea- 

 tures lived at the time, their relics were inclosed in the sedi- 

 ments. But you see how greatly the sediments have been 

 changed to make of them granites and gneisses. If the 

 change almost or completely obliterated the lines of bedding, 

 it must also have destroyed most traces of the included fossils. 

 As a fact, almost no fossil remains are found. Yet a few 

 have been preserved to us. I do not intend to describe them 

 at present ; but you may learn that thy belong to the very 

 lowest grade of animal life. The ages during which they 

 existed may be styled the REIGN OF PROTOZOANS. 



The strata next above, in the lower part of the Palaeozoic 

 Great System, abound in the remains of marine animals; but 

 no traces of fishes or other vertebrates have been found. 

 This was the REIGN OF MARINE INVERTEBRATES. Their 

 exclusive remains extend through two systems, Cambrian and 

 Silurian. In the next higher formations we detect the bones 

 and teeth and armor-plates of fishes. There were many in- 

 vertebrates also, but, as the fishes were dominant in rank and 

 prowess, we designate this age the REIGN OF FISHES. The 

 strata deposited during this Reign form the Devonian System. 

 Next came the relics of the first air-breathers which ever 

 lived. We find their bones resembling those of modern sala- 

 manders or amphibians, though often much more powerful. 

 This was the REIGN OF AMPHIBIANS ; and the corresponding 

 strata are the Carboniferous System. The Cambrian, Silurian, 

 Devonian, and Carboniferous systems make up the Palaeozoic 

 Great System. 



Next, as stated in our last Talk, come the strata which 

 form the Mesozoic Great System. Through this, in addition 

 to relics of amphibians, fishes, and invertebrates, we find for 



