OR CJPPER BARRIER. 345 



be noticed in the sequel, that the summit of Michil- 

 limakinac contains the shells of bivalve molluscas, and 

 consequently must have been covered with water. The 

 supposed dam confining the water in former ages, reached 

 from the extremity of the Cumberland mountain to the 

 Missouri hills. And by the flood which effected its de- 

 molition, the vast tract behind it was drained, the lakes 

 Erie, Huron and Michigan were formed, and the dry 

 land appeared around; while the ruins of sand and soil 

 were carried down the valley of the Mississippi, and de- 

 posited on the alluvial bottom there. 



These imperfect traces may serve to give some con- 

 ception of the former geography of North America, and 

 of the changes by which that configuration has been 

 changed to its present state. 



A List of some of the Organic Remains deposited by the Salt 

 Water before it was drained off* 



A middle-sized oyster, entire, from the neighbourhood 

 of Sackett's Harbour. The shells are in their proper si- 

 tuation, cohering in such a manner as to exhibit a per- 

 fectly natural appearance. The specimen brought by 

 David B. Ogden, Esq. is in high preservation. 



From the county of Ontario, a petrified oyster, six 

 inches long, and four broad, was lately brought to me 

 by Mr. Isaac Adriance. The valves of the shell are a 

 little disclosed, and the space between them filled with 

 a black fetid limestone. Near the opening where the 



44 



