THE STORY OF OUR ROCK FOUNDATION 



47 



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. 32. 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. 



