AMERICAN GEOLOGY EATONIAN ERA. 1820-1829. 



275 



He remarked on the disappearance of the primitive rocks soon after 

 leaving 1 Philadelphia and the appearance of the transition limestone, 



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with occasional protrnsions through this limestone of amphibolite. 

 He also made reference to the red sandstone of Pennsylvania, New 

 Jersey, and Maryland and the calcareous breccia found on the Potomac 



