THE STORY OF OUR ROCK FOUNDATION 



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32 



FIGS. 30-33. Fig. 30. Map showing land and sea when the Potsdam sand- 

 stone was depositing (Upper Acadian). Fig. 31. When Magnesian limestone 

 was depositing (Beekmantown) . Fig. 3 2 . When Richmond shales were depositing 

 (Cincinnatian). Fig. 33. When part of the Niagara limestone was depositing 

 (Mid-Silurian). Land is white, sea finely lined; black shows areas of present 

 outcrop. All after Schuchert. 



