CONTENTS. 



1. INTRODUCTORY Observations 321 



2. The Original Saltness of the North American Lakes 327 



3. The Barriers which probably restrained the waters, in 



some parts of North America, after the ancient ocean 

 had retired 332 



I. THE INNER OR UPPER BARRIER, ib. 



Breaches of this Barrier 334 



1. At the northeast extremity of Lake Ontario ib. 



2. Northern extremity of Lake George 335 



3. By the Hudson River, at Hadley ib. 



4. Mohawk River, at the Upper Falls 336 



5. Delaware, above Easton 337 



6. Lehigh, above Bethlehem ib. 



7. Schuylkill, through the Blue Ridge 338 



8. Susquehannah, through the same ib. 



9. Potomac and Shenandoah 339 



10. By James's River ,.... 344 



11. By the Ohio and Mississippi .,... ib. 



Enumeration of certain Organic Remains found within the li- 

 mits herein delineated. 



A. MARINE PRODUCTIONS ,.... 345 



Oysters ,.- ib. 



Scallops 346 



PectinitCB,. ,,,,,,. ",..,,, ,,,,,,,,,..,,,,,,,,, ,,,,,.,. ib. 



54 



